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Post by sime66 on Feb 19, 2017 16:49:34 GMT
Thanks for your post, pxguru. My feeling is that it’s been wrong for some time, but it’s becoming more obvious as it’s gone on; the idling problem has been hindering my jetting for a while, and this non-starting is a further development, probably of the same issue, but did also happen once last year, and for which I’ve been suspecting my carb itself, but I can’t find a problem there, or anywhere else yet. No good news this morning either – she just didn’t want to start, and I didn’t want to mess about all morning again, so she’s back in the naughty corner. That means on Friday she wouldn’t start, then she started and ran well, but wouldn’t idle, and when I was about to start playing with carb screws she cut-out, wouldn’t start again, and hasn’t since (though I’ve had a good check of everything since then and found nothing to cause it). So now I’m just chewing it over in the back of my mind while I decide what to do next. Firstly, I must just do basic ‘scooter won’t start’ checklist to make sure I haven’t done or missed something simple. Once I know my fuel, air and decent spark are all getting there, I’ll go on to crankcase and barrel. I’ve got compression and crank pressure tests to think about then: · Compression feels OK in the kickstart, but I haven’t measured it – it looks like I need to get myself some kit to do that. · I guess I’ll have to do a proper crank case pressure test too; can’t see any reason to put that off any longer. Depending on whether I find anything with compression or crankcase pressure, I am still ready to change my rings if it looks likely to be helpful, but (if/when she’s fixed) I’ll be running-in again if I do that. I’ll end up doing a pressure test before and after if I change my rings too, but that’s OK. Other things to bear in mind: 1) I drained 220ml of oil with no fuel in it at all; that suggests that there is no leak between crankcase and engine, either direction, through seal or casings. 2) That plug above doesn’t really represent a ‘white plug’; it was intended to show that I didn’t have an oily plug like I’d have expected for MJ145. The temp band on the electrode, and the colour on the surface of the ring for jetting both looked reasonable to me; just no colour in it because I need a good run. In fact, especially as it was a brand new plug that only did a mile or two, it’s probably irrelevant, and maybe it would have been better if I hadn’t posted it. My last plug before that was the plug I took out at the time of my last ‘rough running’ film, when it would only do about 4500 rpm (5th Feb), which ended up being the fuel leak; I think that’s the plug that sat in the engine over Winter though, but it definitely wasn’t a white plug then either. I haven’t had any white plugs, which is why I now believe my CHT gauge has been reading high since I replaced it:
That’s all I can think of for now. I’ll go over the basics again first, and then go on to pressure and compression tests I think that’s the way to go…………
(Edit – for your edit, before I’d finished composing mine)
Yes I mentioned above those two studs came out again – I checked it is the same two as before, and I did use Loctite 603 again; hopefully that won’t happen again, but maybe they are a bit loose on the threads in these old (1982) casings already. They torqued-up OK again, but I have a hunch I’m not finished there yet.
Although I don’t think I’ve lost any oil in that direction (note 1 above), I am aware of this business of sucking oil (or air?) through the very narrow mating surface there (and have since learnt that’s why you place the gasket on the flyside casing, not the main casing). I guess a pressure test will answer that one, and I know for next time to do it differently and why. It’s worth noting this is something that I picked up from Sausage DVD, which I’ve since learnt isn’t the best way of doing it (make a note anyone doing this job for first time). There is a film (in case anyone else is reading this still) it’s from the chap that mijapxman linked to before, ‘mista FreakMoPed’, and he explains why (though I think he gets carried away with his ‘sealing mass’:
Anyway: 1) Basic once over in case I’ve done something stupid 2) Crankcase pressure test
Just thought; I haven't checked the torques on the casings studs, so should do that before a pressure test, especially around crank, so that'll be flywheel (and stator) off again too.
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Post by pxguru on Feb 20, 2017 7:08:37 GMT
It just has to be the crankcase pressure, you have tried everything else!
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Post by sime66 on Feb 20, 2017 10:19:27 GMT
Must be; however I’m busy, and preoccupied for a couple of days now, so I’m just having a quick think of batting-order for next session, before trying to forget about this until later in week (other than ordering compression test kit – see link at bottom). Here's my plan: 1) Towards the end of the week I’ll give it all another thorough check of the basics, and retorque the crank case studs, and have it ready for a test run. 2) If she is then still either not starting, running rough, or not idling I will do a compression test first**. I do know that I used old rings after the seize this time; and aggro starting, not idling/cutting out and not restarting were the same symptoms of worn rings when I first joined this forum for advice, as they are now. 3) I will then do a pressure test – afterwards**, because I have to take the spare, rear and exhaust off, and the carb, so she’ll be immobile, up on bricks, after that. · If only the compression test is poor, I’ll do the rings in the garden, and then pressure test again afterwards to make sure top-end is all back properly. · If pressure test is poor, I’ll have the engine indoors to do the casings gasket, cylinder studs (properly with a stronger Loctite), probably rings (depending on compression test result), and the long-awaited engine mounts - all in one go (which had been my intention over-Winter, but I took a break from it). I sort of need one or other of these to show as a problem, because, as you say, I’ve tried everything else. I do still have Old Faithful up my sleeve if I need a temporary spare to run-around, but I’m sure it won’t come to that; there’s only a limited number of possible causes, so I’m bound to find it eventually. I looked at compression test kits last night; I’ve read poor feedback from lowest-spec manufactures, so think Draper or Bergen would be right without spending a fortune. I need 14mm x 1.25 for the adapter; is this the sort of thing I should be buying? cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=311321824705#ht_3491wt_1397(….and 120-150psi for a decent test result?)
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Post by pxguru on Feb 20, 2017 10:53:47 GMT
I really think you shouldn't run it anymore until you know about the crankcase pressure test. It does sound like it has an issue.
The rings won't be perfect but will not be the cause of this. You could change them while you have it apart but if the kickstart feels ok, then personally I would wait until it's obvious. I have seen them run not so bad with hardly any compression and a kickstart you have repaetedly kick to 'pump up'. If there is still some decent resistance on the kickstart, it's enough to be dismissed as not an issue for not starting. People say 100 psi is the minimum to change rings etc. but they will still run ok down to 80 psi.
You've certainly come a long way from the early days of old faithful. Would be interesting for you to ride that engine again.
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Post by sime66 on Feb 21, 2017 7:44:21 GMT
Thanks pxguru; I’ll still do all the basic stuff and crank case studs, but only take it as far as kicking it for spark and compression – I won’t run it, even up the lane. (I am going to do the compression test because I’m curious, and because I want some data to decide whether or not to do the rings if/when the engine is indoors for everything else – I like the idea of having it back to pre-seize state as much as possible too). Then I will definitely do the crank case pressure test, regardless of anything else I find before then; it’s important to know for sure how it is. I dug my last results from this engine out to use as my benchmark. I’m trying not to think about all this at the moment, but my curious mind keeps wandering back to thinking about compression ratios, compression, rings, temps, efficiency, performance; when I have more time I’m going to get a better understanding of this bit. I’m really curious why worn rings don’t seem to concern you when we’ve taken so much care with everything else – anyway, for now at least, that’s just my morning coffee speaking; my curiosity, not relevant to the actual problem. Yes, Old Faithful, if she gets an airing, would be ‘interesting’; she was a bit of a plodder compared to now, but after my deft rebuild after the (less-than-skilled) clutch-drilling incident, she’s a good engine, and does always get me there and back – eventually…………… Must crack on; the more I get done in the next few days, the longer my weekend is for bringing The Beast back to life. For reference later; my previous results for comparison, as I have them to hand, to save me looking for them again on the weekend: 10psi to 7psi in 1st 5 minutes = 0.6psi/min 7psi to 5.5psi in 2nd 5 minutes = 0.3psi/min 5.5psi to 4psi next 10 minutes = 0.15psi/min vespa.proboards.com/thread/5222/brief-build-update?page=2
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Post by pxguru on Feb 21, 2017 20:04:41 GMT
Will be interesting to see the pressure test result. Even if it is perfect for the milage since it was done, it won't be much like your last test results. If normal it could even be down to 2 psi in 2 minutes. Will assess when the result is out. As for the rings, I like to see things wear out before they are changed. The static compression test is no great issue until it is obviously a problem. New rings also accelerate wear on the barrel, which when so much effort goes into each one of ours. We want them to last as long as possible.
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Post by sime66 on Feb 22, 2017 7:50:32 GMT
If I were a betting man, I’d still go for it turning out to be something other than crank case, but I’ll do the tests as thoroughly as I did before, and we’ll see. It bugs me that the non-starting is/was intermittent, and the performance is good when the throttles opened-up. The idling has me baffled though – that’s been the constant problem since the Autumn. I hadn’t thought about the extra wear on the barrel from new rings, I was more thinking about making it good-as-new again, but that makes perfect sense; I knew there’d be a good reason. I’m still curious about how ring-wear will affect other stuff as it develops, but there’ll be time for that later; I might as well turn the trouble-shooting/fixing into a learning opportunity somehow. Another connected point that’s niggling me is whether I overdid the removal of the seize marks from the barrel. I recall you saying if I hadn’t already taken it apart (and broken a ring in the process because the piston was so stiff on the gudgeon pin, and so used a spare ring from a previous seize), you’d have let the marks sort themselves out, but I got it back to smooth and shiny again, which wasn’t necessary and probably made the bore a bit bigger (and reduced its life, probably). I wonder if that might have made the re-use of old rings worse, and if that might warrant new rings to compensate for it, now it’s done – although I wouldn’t do that again. Anyway; it’s all conjecture until I get out and do some fiddling and finding; I’ll report back over the weekend with some new numbers to chew over……….
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Post by sime66 on Feb 22, 2017 10:59:02 GMT
I think I’ve found something significant!
I snook a quick couple of hours this morning, to get the basic stuff crossed off my list, so I could get on with things when compression tester arrives, before dismantling scoot enough to do pressure test. All stuff around CDI, HT and carb are rechecked and all confirmed OK; I have made a mental note and taken some photos of my float bowl level, but I want to leave that for now because….
…One of the crank case studs behind the stator is not tightening. I nipped them all up with torque wrench, but the one at 4o’clock wouldn’t tighten (or I over-tightened it this morning and stripped the nut). Either way I’ve either found or caused a definite problem.
A couple of questions arise, which I’ll try to answer for myself later, but will jot down here in case there’s some input while I go about my business: 1) Does this make the pressure test pointless, or should I do a before and after test; I think probably still best to do both to confirm it is a/the problem. I know it is a problem, but I don’t know it was the problem, if you follow me.
2) I have a spinning nut, which will probably need drilling to remove, and the stud replacing; if I do manage to get the nut off, how accessible is stud-withdrawal from the other side if I try to do it in the garden? – That’s if it’s even sensible to do just one stud without either loosening/replacing and retorquing all four, or splitting the casings to check the gasket anyway. (I’m trying to decide if it’s already become an indoors-job or not).
(Edit: I've realised those four studs are in the main casing, not through-bolts like the rest, so it's probably going to have to be engine out, unless it turns out it's just the nut and I can get it off without messing the stud threads up - if they aren't already.)
I’m sort of glad I found something, but have a slight niggle that I just caused it rather than discovered it, but either way I need to decide how best to go about fixing this one to see whether or not it was the cause.
Must crack-on; I’ve got myself filthed-up and behind schedule for today, and I’m not sure whether I’ve made progress or made myself a new problem – either way it’s something specific to think about now……………….
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Post by pxguru on Feb 22, 2017 21:09:09 GMT
That certainly is something. Need to do the pressure test to prove it. Not sure that would leak enough but probably wouldn't suck in much gear oil from that position. I expect it to be just the nut, as those studs are difficult to strip. If the pressure test is bad it woul'd explain why yours is now so different jetting to my tourer.
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Post by sime66 on Feb 23, 2017 10:49:12 GMT
Only half-hour on it this morning; grabbing time when I can at the moment. Still narrowing it down though, and pressure test will be the next job, but more time needed for that one to take a few bits off scooter first. Anyway, I do have a spark, but I do have very low static compression; I tested it twice and got 68psi & 70psi, so that’s confirmed as requiring attention. Next two jobs: 1) Pressure test………….coming next, honest. 2) Trying to get the spinning nut off without buggering the stud threads, and with pretty limited access – any advice here appreciated, however obvious it may seem – this sort of thing isn’t my strong point (not sure what is actually). That’ll do; more soon.
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Post by shipscat on Feb 23, 2017 20:38:29 GMT
hi sime66 to get the nut off try with some long nose vice-grips clamp on the nut , pull hard whilst undoing remember righty tighty lefty loosey hopefully the nut will find the thread and start to undo enough to get a screwdriver in between the washer and nut assuming you have a gap to get your screw driver in , twist to put force on the back of the nut at the same time try undoing the nut with a socket fingers crossed it will come off, do not spend more than 10 minutes doing this if the nut does not start to undo it will not come off this way !!!
much more aggressive and not really recommended the last resort without welding gear you will need to buy another stud but you wont need to split the engine set up your dremel with a small cutting disc and set about cutting the nut to split it in half carefully cut one side of the nut then do the same on the opposite side note you wont be able to cut all the way through the nut without damaging something else the idea is to weaken it and split it open with a small chisel and hammer
the ideal no p*shing about way is with a mig welding machine , tack weld nut to stud remove replace is there garage/bodyshop close to you ?
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Post by sime66 on Feb 23, 2017 22:25:06 GMT
Thanks very much for that, Shipscat, Pulling up onto any remaining threads and turning did seem like the way to try first, and I do have some long-nose vice grips; I’ll give that a go first for sure. I think I tend to be a bit heavy-handed and make things worse before stopping and thinking when things don’t work, so I’ve probably already spun it a few too many times to be sure it wasn’t coming off, but I’ll give it a go. It’s also the one that has very little room around it, other than to get a socket on it, which doesn’t help. Getting something under to lever the nut upwards too; I’ll give that some thought and see how much room I have to slip something in. I found the studs I would need if it did need replacing, but I hadn’t occurred to me that I might be able to do the job without splitting the casings, so that’s another really useful tip if it comes to that, and I do have a chap who could weld the nut on and extract the stud if I need help. I think, if the nut isn’t coming off easily, it might be better to weld it on because there’s only a short length of stud there without splitting the casings, so that’s probably better than cutting the nut of and butchering the short exposed length of stud, though I could cut the nut off myself; I’ve had to do that with a hub, but it makes a mess of the stud. Also, I think I’d be much better off trying to keep the old stud, than replacing it with a probably lesser quality one like any of these ‘OEM’ ones are likely to be: www.sip-scootershop.com/en/products/stud+m7x50+mm+_47162000www.scooter-center.com/en/product/5150011/Stud+M7+x+50mmwww.beedspeed.com/vespa-engine-case-selector-stud-p-1785.htmlTo give a better picture; here’s what I’m looking at now, and the old stud itself from an earlier photo:
Thanks for your post; it’s a great help, and gives me a few things to try.
Either way, it isn't drastic; I've quite a list of other jobs I could do if I have to have the engine out and split, and at least now I have something specific to sort out, instead of the drawn-out trouble-shooting.
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Post by pxguru on Feb 24, 2017 7:48:57 GMT
That is something else significant! 70 psi won't run well at all. Probably will only bump start, then not go very well, splutter at low rpm and misfire occasionally Not sure how it is possible that your rings are so bad but they are. To hijack your thread for a second. I did a Winter strip of my Polossi yesterday (still in pieces), with the intent of; Repaint exhaust, change clutch, slight port re-tweek, fit new MRP cylinder head and check and adjust all. What happened was, clutch inspection showed it is ok for another season but piston rings are not ok for another season. Ring gap has grown from 0.1mm to 1.2mm, which although not quite so bad, won't last the year. I have a new set already, so just need to get on with the porting tweek before re assembly. Will be interesting to see what the ring gap on yours is with only 70psi If you squash that nut a little it might grip the threads enough to get it off.
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Post by sime66 on Feb 24, 2017 11:07:39 GMT
From June 19th 2016 vespa.proboards.com/thread/5222/brief-build-update?page=23The ring gap on the part-worn rings I re-used in June, measured using piston to push them 25mm down, but on barrel before I cleaned it up were: ‘Scored bottom ring’ (from Jun 2016 seize) = 0.6-0.65mm; ‘Old spare ring’ (from previous seize) = 0.7-0.75mm – those are 25mm down using piston” We discussed acceptable gaps at the time, several sources agreed: “Piston ring gap on assembly = 0.25mm - 0.4mm. 2mm max permissible.”· I’ll measure them when I replace them now to see what I had for the 70psi. · Exhaust is off for inspection and painting; I got paint for it yesterday. I checked, and I first installed it new in April 2014 · It had crossed my mind to have a look at the clutch while I’m messing about · I’d quite like to get my engine mounts done, though they weren’t as bad as the ones I replaced on Old Faithful · I can sort my barrel studs out, to prevent them keep coming out · I’ve got the spinning crankcase nut to sort out Pressure test results:……No tidy little table for comparison with the one above I’m afraid; I could only get it up to 6psi, which went down to 2psi before I’d even started timing, then dropped to 1.2psi withing two minutes where it stayed, but that is pretty much atmospheric because when I released the valve the gauge stayed there anyway. I checked all my seals, valve and bungs and tried several other pumps, then redid the test and couldn’t even get the 6psi again. It might be my equipment or method (both exactly the same as for the results above), or it might just be really bad. With the access and visibility I have, I am not entirely sure which; I could check everything and try again, but it feels like a waste of time.
To be blunt about it, I’m sick of fannying around up the lane and scrambling around in the garden with no access, limited visibility, worrying about neighbours and weather and waiting for free daylight hours, and I’ve decided it’s time to get the engine indoors and do all these jobs properly where I can work in a clean, undisturbed environment with decent lighting a power supply, and full working-height access, and only put the engine back when I’m satisfied everything on the list is spot-on again. There’s enough of a list to warrant it, it needs doing properly, and I can’t do that rolling around in the garden. Once I’ve got myself organised indoors, it only takes an hour to get the engine up here; I'm going to do that over the weekend, and get it all sorted out.
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Post by pxguru on Feb 24, 2017 15:33:46 GMT
The saga has turned a corner now. It really looks like old faithful is soon to have an airing. Good work getting the pressure test done. Results pretty much confirm how it starts, runs and rides. I really hope the main seal has torn. This will give the best outcome. Whatever it is, there is no doubt it is fixable. Might as well get everything you want done while it's out. New mounts, case stud, rings, main seal and gasket set should do it. Might as well put in a double hard crux if it's looking worn.
edit; One point to mention about the compression. With the lack of crankcase pressure the compression will be somewhat lower. You might just make bare minimum with it sucking mixture but still going to need new rings in.
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Post by sime66 on Feb 25, 2017 9:42:57 GMT
09:15 My baby is tied down with her arse in the air, The Beast is on the operating table. Glad that's decided and done, so I can work properly now.
Now we can have a proper sort-out. Old Faithful can stay where she is until full diagnosis is complete. I'll get everything properly sorted before either engine goes back in - some neglect last Autumn/Winter on frame and cables means there's work there too if I'm going to be thorough. Yes, hard crux was on my mind; we'll see how this one looks if/when I split the casings.
I noticed your edit re crankcase pressure and compression; I'm going to start with a crankcase pressure test to be certain my results yesterday were correct, and take it from there. I'll also be measuring the ring-gap as part of the top-end stuff on the list, but I I'll end up with new rings for sure. I have rings, seals, gaskets etc. 'in-stock', but I'll do a shopping list for the rest as I work through it all. Top-end work, spinning nut and crankcase re-check of pressure test will determine whether engine gets split, I think. Happy days - whatever it is, I can sort it.
(Not now though; clean up, tool tidy, wash up, bacon sandwich, rugby..................)
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Post by pxguru on Feb 25, 2017 10:43:07 GMT
Good work! If there was no bacon, life or sport I am sure the beast could be back on the road by tomorrow but it's cold out so take your time.
I think you might have had this issue getting progressivly worse for a long time. Jetting is not normally so hard or confusing, as you have had to put up with.
You can't put it back in without giving the clutch a once over for cracks and damage. If you take the clutch off before the pressure test you will be able to squirt something in the main bearing to confirm any leak from the main seal.
With my Polossi rings I would have been happy for them to go to 1.5mm gap before changing them but as they are removed anyway, I have a new set to hand and most importantly I have had about 4 years on this barrel and no matter how much I thrash and abuse it it won't blow up, so this will be the last set in it for now and then its time for a my "new barrel" to get an airing
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Post by mijapxman on Feb 25, 2017 16:34:54 GMT
Sime, hope you get it fixed without too much hassle. May be worth looking at the BGM engine mounts,I fitted a complete set to my 200 engine, using talc to help them in. Haven't put the engine in a frame and tried them yet, tho.😉
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Post by sime66 on Feb 26, 2017 12:04:40 GMT
I’m not rising to any joviality about how quick I can get it back in; I’m interested in doing it as well as possible, not as quick as possible, I’d like this to be the last time I have to have this engine out for a good long while. If I get held up or browned off, Old Faithful can have a spin; for now I’m happy to have this indoors for a thorough sorting without any time pressure at all; I'm much happier working like this already. Mijpaxman; I’ll deal with yours first because it’s quickest reply – I used those BGM engine mounts last year on Old Faithful, and bought two lots then, so have another set for this engine; I’m much happier having BGM that pot-luck unbranded – there’s a whole thread on the subject from my last go at it. I also, have not ridden on the engine I fitted them to yet: vespa.proboards.com/thread/5607/selecting-replacing-engine-mountsNow to business:My overnight (mare) was this nut, so after giving the casings a quick Gunking this morning, I tackled that (all other matters seeming less important if that was going to be a proper problem and preventing me splitting casings AND tightening crankcase studs). Anyway, the good news is that I did get the nut off; I held the socket on at a bit of an angle to get some friction between nut and stud, and got a small screwdriver up under it (edged in through the spring washer). Anyway it is off. I then thought I’d better make sure I didn’t have the same problem with the other three, and I’ve ended up partially undoing the two top studs (10 & 2 o’clock, if you like). I’ve taken some photos of the stripped nut and stud, and although my eyesight is becoming a real problem (years of fine work on drawing board and staring at computer screens), I think the stud and nut are both knackered; there may be some curls of aluminium still stuck in the stud, but it’s hard for me to see for sure. Anyway, given that two of the other studs are coming out as well, and given the fact that the same is happening with the barrel studs, I think these old casings might be needing some proper, careful replacing of the best quality studs I can find, stuck back into thoroughly cleaned-up holes with the strongest Loctite (or better) I can find. I think this means I should split the casings and do that regardless of anything else, and probably first job. Unfortunately, because those studs came out, (and I didn’t want to screw them back in) I didn’t repeat the pressure test; maybe that doesn’t matter, but it’s probably too late now. Here’s some pics of that bit:
I then had a look at the clutch, which is as good as new! I’m impressed with that 16 rivet SIP whatever with reinforced circlip; I’d been expecting a big expense there to upgrade it for this engine and weight. Anyway, there is no damage to castellations, no cracking, it spins smoothly under the resistance of the oil when compressed. The extra-wide circlip had spun but not opened, and I put it back between castellations. I could take it apart to look at the corks and plates, check the rivets are tight; I’m inclined to leave well alone, but probably should. I gave the primary a spin and inspection too, and it too shows no signs of any stress, damage, or loosening of those rivets either. I did mean to mention last time, when we were talking about crux, that the clutch and gears on this engine, since initial setting up and cable stretching, have always been very smooth and nice to ride, so I’m hoping/expecting the crux to be in good shape as well, but open-minded about that upgrade. Here’s some pics of that bit:
It seems to me I could now retighten three out of four of the crankcase studs and do the pressure test (but I'm inclined not to tighten those studs back into casings); or have the top end off and casings split, and replace all these studs properly before proceeding; I’ll listen to opinions on that, but I think I know what I’d do. I realise I haven’t got a conclusive answer about the main seal, but I can do it anyway, or decide after inspection; I should say that my drained oil is 250ml, dark, no separation overnight, and smells just like new oil. It must seem most likely that crankcase sucking is more likely to be the problem now anyway, doesn't it? Either way, the barrel can come off for rings and stuff next, and perhaps that'll give a clue inside the crankcase too; but guess what – it’s more rugby today, so that’s your lot for now!
(I meant to say, I see you’re letting out little bits of info about Palossi tweaks, and remembered you have a pre-magicked barrel on the shelf waiting, also that you’re doing port-tweak and new head with it now; it’s all going in, but I know you’re a bit more protective of info on that one.)
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Post by pxguru on Feb 27, 2017 5:42:00 GMT
That clutch looks new! I think you are right to be impressed. No point taking that clutch apart. At least you know you have the right clutch for your engine.
Did you repeat the pressure test with the three nuts back on? The other studs look to be ok. That one must have been cross threaded at sometime, hard to tell now. I wouldn't go changing the others if they don't really need to be. Might as well split it now anyway but useful to know if it is the seal or the gasket.
No more rugby but still something Italian winding you up.
My Polossi is all back together and running been quite a big tweek so going to need a full rejet. It's sort of the last go with it before the new barrel goes on. The MRP race head is good for both barrels so no money wasted. Is nothing much of interest for here only to point out that I am not always lounging about drinking beer.
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Post by sime66 on Feb 27, 2017 6:34:50 GMT
I haven’t redone the pressure test, but I can; I was unsure: a) whether it was wise to torque those studs back down, or whether I might give myself a new problem; I’m thinking about the threads in the casings. b) whether a pressure test would be worthwhile with just three studs. (or with the clutch off, maybe they'll hold enough for me to see if anything is passing the seal?) c) whether this obvious problem combined with info about the drained oil already confirmed that the seal was not the problem. d) Whether a torn seal might be pretty obvious anyway, when I split the casings. I’m quite happy to go either way with it; you think I should still try to do a pressure test before splitting? I’ve left it all intact so that I can still do it; maybe I should then.
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Post by pxguru on Feb 27, 2017 7:00:34 GMT
Just nip up those three nuts and quickly try the pressure test. When you take it apart it should be very obvious if it is the seal but doing the pressure test it will also be very obvious it is the seal. The problem comes if you split the engine and it all looks fine inside. Yet it wasn't holding pressure, so there must be a fairly big cause. Confirming it is or isn't the seal before splitting will save confusion. It's unlikely to be two things......surely
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Post by sime66 on Feb 27, 2017 8:59:29 GMT
Righto, thanks; will proceed with caution and report back........
.......Ah ha!
I’m happy the main seal is OK now.
The leak I was getting in the garden was just my plate on top of the inlet, so with that sorted, and the three remaining crankcase studs/nuts retorqued, I was able to hold enough pressure for ten minutes to have a nose round. Still vague on exact pressures because I had to use the bigger gauge on the compression tester through the spark plug, which only has 4 graduations to 25psi, so not very accurate for low pressures, but it held the first graduation (5/10psi) for ten minutes, and went back to zero when I pressed the pressure release on the gauge. I also laid the engine with the seal/bearing horizontal and filled it with oil, which didn’t drain through the seal, or bubble-up under crankcase pressure either. I think that’s got it covered now. I’ll revamp my testing kit so I can do a proper timed job of it again once all the engine jobs are done.
Hopefully it’s just that crankcase stud and my rings combining to give enough of a compression problem for the symptoms, which were never drastic (starting/idling), but needed decisive action to get them sorted; I’m pretty optimistic about that now. I’ve got the rest of my list to work through too. A carb stud came out as well; I must have a serious sort out of all these engine studs and get them back in permanently; some aggressive degreasing chemicals and industrial permanent threadlock needed.....
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Post by sime66 on Feb 28, 2017 9:37:18 GMT
Here is the real problem:
Glad to say, it doesn’t seem to have scored the barrel; I’ve only taken photos before cleaning up for now, while I have a think about it. I checked, and those rings definitely line up with their pegs, so that wasn’t the cause. I was never really happy about using old rings, that I felt were brittle, but I do understand why. Given barrel is OK (after a proper clean and check to confirm, I have an old DR piston (and new rings), or I can buy a brand new piston and rings; after this I think I’d be inclined to start from new. Glad to have found something. Glad that it isn’t a crack in the casings. Glad (I think/hope) I’ve had another close escape with this barrel – lucky I wasn’t happy in the lane, to take it further.
More later……………………..
The points that the ring failed does appear to align with those 'V' divisions in the boost transfer; perhaps I should flatten the tops down a bit. Even if that is the cause, it still didn't happen on new rings, just the reused ones.
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Post by pxguru on Feb 28, 2017 10:56:20 GMT
Well, I am sure no one was expecting that! Rings just don't do that unless there is a sieze up. I don't see enough marks on the piston for a big sieze. If there is no crank case pressure then there would be a lack of 2 stroke getting up the barrel. Did you get the casings opened yet? Looks like the barrel will be fine with a new piston, if that is just a minor scratch that you cant catch your nail in.
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Post by sime66 on Feb 28, 2017 11:43:21 GMT
I’ll split casings next, but I can’t get dirty again until tonight or tomorrow; there is no hurry now. I’ll clean the barrel up to check it’s OK too. I wasn’t actually that surprised to see it; just glad it didn’t do more damage. Whether a seize caused it or it caused a seize - who knows, it’s something definite that I can fix now, and I’ll be checking everything, pressure testing, and running-in rich and spluttery to start with anyway, so can keep an eye on it. The new piston will need some work before I do that, and I need to do an inspection of everything else inside before I do a (probably SIP) shopping list and order the piston, so it’ll take as long as it takes now. I can do a few jobs on scooter/frame; maybe this weekend, while I’m waiting for stuff to arrive, If mood/life/weather etc. allows. (I see you're online as I post, Vespasco; hope you're having fun wanderin' about).
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Post by pxguru on Feb 28, 2017 12:03:42 GMT
Not sure if you already have a spare DR piston handy but if not, one thing you might want to think of is a thin ring (steel/chrome/moly etc.) piston. Not sure what is possible for your bore but there might be something. The iron piston rings you have are good for occasional high rpm use but not too much or too high. As you are unfortunately in this position. It maybe possible to find a thin ring piston that near enough (or exactly) fits your bore. This will also give more high rpm power but thats just a bonus.
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Post by sime66 on Feb 28, 2017 20:42:39 GMT
Couple of hours this evening; cases now split, and stock-take of jobs before deciding how to proceed: 1) Piston: Yes I have a spare (used) DR and new rings, also a new DR with all the new bits is £50. I anticipated you mentioning alternatives; there is a GS 177cc Piston in Ø63 and 63.5mm for £100. That really is third on my list of options at this stage though; I just don’t need any unnecessary expense or work on this at the moment. Perhaps that’s a good option to have up my sleeve if/when I need an o/s piston, if this barrel survives long enough, but I don’t think so this time. www.sip-scootershop.com/en/products/piston+grandsport+177cc+_12037100www.sip-scootershop.com/en/products/piston+dr+177cc+for+vespa+_121901002) Barrel: looks and feels OK after a clean-up (just Scotchbrite pad); you can see the main mark on the photo, but barely feel it at all. I’ll check the ring gap with new rings to decide if it’s still going to be OK or not, but I think so.
3) Crank: I haven’t had the crank out, not sure if I need to, and don’t want to disturb the seal if I don’t have to. I have noticed some signs of heat around the big end bearing, which I’ve compared with photos from before, and there was quite a lot of colour there already from when this crank was in Old Faithful, and it still feels fine to me. If this is a worry, I do have a recently checked spare crank, which would need cutting for timing. Also if it is a worry then I need to know why it got so hot before just swapping stuff. Also deciding on this will help me make decisions about other items. If it all becomes too expensive or too complicated/work-heavy, then Old Faithful can go back in until I’m in the mood for this and have the money to spend. I’m not willing or able to chuck £100s more at this engine at the moment. I’ve checked the web and sealing pad, which are both pristine, and there’s no debris or engine oil in the crankcase; no bits of ring, no oil sucked in – nothing in there that shouldn’t be.
4) Crux: inspected and does need replacing. All gears are fine; 1st was fairly old anyway and not important, 2nd and 4th are pristine, 3rd shows only a little wear. Hardened crux is £50; still not really sure if it’s better to have a soft crux and little wear on gears or hard crux. I think I’ve got a spare or two somewhere as well. End-float on gears has loosened-up a bit to 0.2mm; it was very tight on the build.
www.sip-scootershop.com/en/products/cruciform+serie+pro+by+mj9+_87029100
5) Studs: I have studs in barrel, crank and carb that keep coming out. I want to replace the studs and any others that are not secure. I’d like to find a permanent solution to this; degreasing holes (which is where I think I’m going wrong) and permanently securing new, quality studs (where needed). I’ve been using Loctite 603 and it isn’t doing the job, although it’s supposed to be suitable for situations where degreasing is difficult. I’ve got a stripped one in the casings to get out as well, but, given how easily the others keep coming out, I don’t expect I’ll have a problem there.
www.sip-scootershop.com/en/products/stud+m7x50+mm+_47162000
www.sip-scootershop.com/en/products/stud+m7x36+mm+_52100000
www.sip-scootershop.com/en/products/cylinder+stud+m7x140+mm+_15065700
6) Main gasket (oil sucking?): I don’t think there was any oil sucking; I think I just need to put it back carefully as it was with a new gasket when I get to that – no problem there.
7) Engine Mounts: I have the parts for this, and it’s just extra time when the casings are back together - no problem.
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Post by pxguru on Feb 28, 2017 21:06:33 GMT
The only worry so far seems like the big end. This would also point to poor lubrication, low crankcase pressure. I would take the crank out for a good look. Not much time at the moment. At least the main seal is still in its recess.
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Post by sime66 on Mar 1, 2017 12:33:01 GMT
Here’s a few more views of the crank, which I intend to spin on the jig as it’s out of the engine, and compare the big-end bearing play with the other used one I have, but to re-use this one unless you advise otherwise:
Here’s the main seal, which is in the same condition as when first installed, as is confirmed by pressure test and oil drain/bubble tests. I’ve also shown the Inlet pad, which is also as installed:
I’m also not convinced there’s been any recent overheating issues, or recent seizes because:
· The colour on the crank is more likely to be from the previous two known seizes (one in Old Faithful years ago and one in The Beast in June 2016); I have old photos showing colouring before it was first installed in The Beast. · There are no seize marks on the barrel, just the single score-mark from the broken ring, and light-brown burns on head, piston, down barrel and in exhaust (surely indicating less than complete burning, not overheating). There’s no pitting of crown or aluminium deposits anywhere either. The only damage I see is physical damage from a broken ring. · There is no leak at head, exhaust or carb, nor is there sucking at crankcase, and on the second attempt indoors the crank case held pressure, even with one crank stud stripped (which I think was recent, and due to overtightening whilst checking – it was never cross threaded because it hasn’t been removed since the build). I have shown the main seal is good; (it held pressure, didn’t leak oil and didn’t bubble through the oil when crankcase was pressurised), and the sucking is now disproved as well. · I still think this was caused by old rings, giving increasingly low compression (idling and starting problems) and then only breaking quite recently to give the damage I found; it would not have started with that damage, and it was starting OK only a few weeks ago (on film below and previous week, film above), and it hasn’t done much damage because I was either stationary at the time or very soon after. I think the most the piston has moved with a broken ring was when I did the compression test. That first photo of ring damage in previous post above is in-situ before any cleaning; there is no sign of burnt/unburnt fuel squeezing past broken rings, burning down the piston; just the same sticky brown that is everywhere else, which I highlighted and queried on Feb 18th. The film below from 17-02-17, with AC185 & BE2 (and MJ145 to deal with the previous week’s CHT indicated high temps), shows it running OK, and then cutting-out at idle for the final time before the complete non-starting issue and subsequent trouble-shooting, which led to the engine removal and split; I do not believe this damage existed before then because I would not have managed that starting and riding in the film. My indicated temperature for that short ride in the lane was 150°C (indicated high, lower than the previous week) and if anything my CHT is reading too high; previous readings of 170°C have shown no problem with the plug. The Feb 5th (42/160, 135MJ, BE3+2, AC160, rough running) plug I posted on Feb 19th was very rich.
I do want to be thorough before putting it back together, but I really am not convinced that this has been too hot recently, or that high temps (for whatever reason they may have existed previously), or a seize, were the cause of the ring failure. Recall how brittle I said the ring was before; why then wouldn’t the other one be equally brittle?
This is the last time it ran, and the first time it didn't re-start, and it hasn't started since - just kicked unsuccessfully, kicked to check spark, and compression test since.
I’ll continue to check all possibilities suggested, to remove them from the list of causes of any other problems, but I think new rings, and sorting out the studs I’ve since damaged or are persistently coming loose, will be all that is needed to get this top-end resolved. I also need to decide whether or not this crank is still good to use, (which I think it is), as a separate matter to the possible causes of any overheating if there was any –the heat to the crank does indicate that there has been a problem sometime, but is the heat to the crank actual damage to the crank big end bearing as well? Can I still use it? Then there’s just some minor gearbox stuff, and the external stuff.
For now I’m completing investigation, trying to agree/decide on cause, and deciding on parts before doing an order.
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