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Post by pxguru on Mar 17, 2017 9:23:53 GMT
The up to 5 base gaskets thing, only really applies to a fully standard PX125.
On a T5 the stroke is shorter (size does matter) and therefore the porting is much more sensitive, probably one extra will be an improvement any more will need some calculations and probably a modified head (maybe like this one posted here).
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Post by pxguru on Mar 16, 2017 17:51:08 GMT
I have one of these in my Polossi 221. Really happy with it. I do remember it was a struggle to get working right. I started with a clutch cover spacer on mine, as SIP say but after a few weeks of slight oil leaks I took it off and Dremelled out the clutch cover round the edge where it touches. Been working fine ever since.
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Post by pxguru on Mar 16, 2017 3:09:48 GMT
How you getting on with this jetting? Any better?
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Px 200
Mar 15, 2017 10:47:04 GMT
Post by pxguru on Mar 15, 2017 10:47:04 GMT
Should be no problem with the DRT carb. All the mods should be done to it. If you haven't already check the flow out of your tank is enough, like in the videos.
Check the overflow out of the carb float bowl is not blocked or obstructed by your flat reed block (fuel doesn't go in if air can't get out)
What is on top of your carb, Vortex, filter or nothing? And is the carb box connected by rubber hose to the frame?
Start with a 55/160 BE3, AC160 and 150MJ and see how it runs. Should be spluttery and smoking way too much.
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Px 200
Mar 14, 2017 13:14:20 GMT
Post by pxguru on Mar 14, 2017 13:14:20 GMT
The Polini 210 is a good solid kit. Did you get the head too. Why did you change the 28mm and reeds for this LML type reed and Si24? Must be some good reason. And it's not to run autolube with that block in the way.
Now you have this set up the first thing you need to do is drill the carb. At least 1.8mm is required for a 210. We have drilled ours to 2.0mm and seems to be ok. The standard drilling will struggle to supply much more than a 140MJ. Once you get it to run black on a 150MJ then start jetting in.
have a look at these tips for some ideas
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Post by pxguru on Mar 13, 2017 4:30:40 GMT
I think you are getting close to your original loss of speed problem now.
I would have the flywheel off, have a look then stab around with a multi-meter. As far as I know the spark power and lights power are reasonably separate but if there is some short circuit going on at the stator, then they might not be so separate anymore.
The only time I ever see proper backfiring is when the woodruff key has sheared and then the timing is way out(on a tuned high rpm engine the woodruff key is a service item!).
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Post by pxguru on Mar 12, 2017 12:06:43 GMT
Don't think there is any danger of you getting the train home. Sounding like she's running well again. Pulls quite hard from low rpm. A few more of these runs and it's time for a long ride out, maybe to the seaside but just for a look. Beginning from a clean sheet with 55/160, MJ145, BE3 and AC160 will get the job done quicker. Tweek only what needs it. Get the pilot and mixture set up first and if it revs out enough the MJ can stay where it is until run in. All in all, I think you got away with this one quite cheaply
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Post by pxguru on Mar 8, 2017 17:36:42 GMT
Its not really about rpm, more about where the throttle is. Just be sure it stays under 1/4 throttle and it will be running mostly on the pilot jet. If you do it twice in both in 3rd and 4th you will have a clearer idea of how it runs and if its safe.
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Post by pxguru on Mar 8, 2017 17:25:14 GMT
Those mods to the inside of the piston don't need to be done on the inside. And I cant imagine they would make the pin tight. Chamfer the piston ports from the inside too though. Before fitting a difficult piston put the wheel side circlip in, then give it 30 minutes at gas mark 5 and the pin will just slide straight in.
The loctite 270 will do the trick. Just make sure this is the last time any of those studs ever come out again. When you wind them in stop with a few theads showing.
Surprised you didnt get the thin ring Grand Sport DR piston. Is double the money but there is always the 1st oversize option for much later on.
SIP say that the hard crux doesn't wear the cogs any more than usual. I have no idea if that wizardary is true but I have one in mine with a new set of gear cogs, so we will see how it looks in a year or so.
Be sure to get a good pressure test result before fitting the clutch.
I would imagine you are looking forward to starting with half a kick again.
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Post by pxguru on Mar 8, 2017 3:27:10 GMT
Been a lot going on behind the scenes. You will be the small block engine mount expert before long, if not already. As I remember the beast never went right after the last rebuild. Maybe the top piston ring was cracked since near then? Now you have your compression tester it will be much easier to keep an eye on it.
The main reason for taking out the 0.2mm copper packer was to reduce the max rpm. It was revving too high which means that the bottom end would be flat and it wouldn't pull 4th so well. 0.2mm has no great effect on the compression, not sure it would even notice. Either way its not permanent and will be as you liked it pre re-build, so least it will be running fine for the Summer.
Did you buy a new piston or re-using the original scuffed one from the very first build?
There are a lot of opinions to running in just rings. No additional oil and just the three heat cycles is all I ever do. Nothing bad ever happens and they seem to last plenty long enough. I am not usually running in cast rings though so I suggest not too much prolonged high rpm stuff for the first few tanks or petrol.
I think you will find this time round the jetting in will be confined to a weekends work. Once its running great again it won't be such a chore.
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Post by pxguru on Mar 8, 2017 2:59:25 GMT
With the idle jet covered by the Polini venturi, the slow running could be affected. This might be all it is. The size of the carb box lid and the smaller size of the Polini air filer would only cause restrictions at higher rpm and more open throttle. For the 1/4 throttle problem you have here it's not such a big deal but something you should think about anyway because once the pilot jet is sorted it's onto the WOT runs to set up the main jet.
Once we find out what this problem is the 1/4 throttle plug chop will be lighter coloured with a 50/160 pilot jet.
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Post by pxguru on Mar 7, 2017 3:39:41 GMT
Nice try Pek but the air temperature difference won't change a black oily plug into normal running colour. There is something wrong that is making it run black. A 50/160 should run well in yours, maybe 52/160 or 48/160 but either way pretty close. The smaller sized pilot jet air holes have their uses but will just make this really complicated. As jimscoot says, could be a slight fuel leak. This would make it hard to start for sure. I doubt it is the main seal or you would be complaining much more about how it runs. There is something clouding the issue. Timing at 18 degrees is where it should be for now. Once it is all set up and running great, upping the timing timing a degree or three and being sure there is no issue will make it a bit faster, especially in mid range. If you have the same venturi intake as Sime66 you might want to see what he did to his in this thread vespa.proboards.com/thread/5222/brief-build-update?page=18Modified so there is no need to keep taking it off and less restriction to air flow into the jets.
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Post by pxguru on Mar 6, 2017 4:17:36 GMT
Why do you think a lightened flywheel will make yours go better?
It does sound to me yours has something wrong. It should never be difficult to start with what you have done. No jets you have are big enough to make a black oily plug on the 1/4 throttle plug chop run. This is due to something else a little more ominous....unless you just need a new spark plug. Really hard to tell from here. As soon as the throttle is opened past a few mm the mixture screw has no effect. Anything happening after that is jetting.
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Post by pxguru on Mar 6, 2017 3:57:55 GMT
Easy to get things confused. More oil without up jetting does run leaner. Basically why a pre mix P200E has a 118 MJ and an autolube PX200 has a 116.
Just mild nip ups where you can re-start it before it rolls to a stop are usually nothing much to worry about. Ideally slipping the barrel off when you get home and lightly rubbing down the seize marks on the barrel and piston will help it not happen again so quickly.
Your jetting is way out. For running in your 177 should have at least a 128 MJ and the extra oil in the tank. After it is run in you need to do the same as Pek is doing in his thread.
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Post by pxguru on Mar 5, 2017 4:53:33 GMT
Didn't go quite as I expected with the pilot jets. As jimscoot confirms 50/160 should be about right for yours and 55/160 should make it run blacker. Main jet, atomiser and AC are all ok for now. You should have your carb drilled from the standard 1.6 out to 1.8mm (but that won't help this issue).
What also makes them difficult to start when lean/without choke, run black and smoke is a blown main seal. How is the gearbox oil looking? As Sime just confirmed with his; if after a decent run out, the gearbox oil is really still ok (quantity/viscosity/smell) then the main seal is likely to be fine.
Timing is another tweek and without a fancy box on the CDI the IT mark at 18 degrees is a good place to start. As a general rule the earlier it sparks the more power it will have, that is until it all melts and needs a full rebuild. With all tip top mechanicals, a centred head that fits your piston properly and a well set up carb, it is possible to run up to 21 degrees with little problem. It does take a while to get really set up well and timing the same (but opposite) as jetting begin safe at a low setting and work your way up one degree at a time.
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Post by pxguru on Mar 3, 2017 3:40:55 GMT
In my opinion (and there are a lot of opinions here) a 55/160 IJ is richer than a 52/140. I would have gone down to a 50/160.
What size main jet, atomiser and air corrector is in there now?
With your main jet within a few sizes of correct (sounds like yours is), to check the pilot jet size, ride along for several miles at no more than 1/4 throttle and check the plug colour. Try to get a digestive colour here before changing the main jet.
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Post by pxguru on Mar 2, 2017 10:40:38 GMT
That seal still looks new! The cruciform isn't fully worn either (you know Vespasco would just turn it around and put it back in).
As I remember there was nothing much wrong with your old DR piston.
It will jet in easier this time round, so no more getting hot
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Post by pxguru on Mar 1, 2017 13:17:08 GMT
Still no time but a few comments. Crank looks fine. Many of the heat marks are from assembly. How does it look against the original pictures?
Good to see the main seal still in place. It might be worn. You have an angled picture showing the seal lip? Why did it not hold pressure the first time it was tested?
If the only issue is the broken ring, then this was broken/cracked at the time of the first issues with poor tick over and starting.
If you can re-use an old piston, this will be a fairly inexpensive re-build.
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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 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 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 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 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 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 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 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 pxguru on Feb 23, 2017 7:58:40 GMT
Just one point to add, looking at the photos, normally there would be grease everywhere. Are you just dry fitting these for 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 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 pxguru on Feb 21, 2017 6:41:04 GMT
Still something wrong with it for sure, a standard 125 should always manage 55mph on the speedo and maybe even 65mph on the speedo........on a really good day.
Have you taken the cylinder head off and cleaned off all the carbon? Sometimes there is quite a build up in the exhaust port. Take a picture of the top of the piston (before and after cleaning) and we can see how bad the pinking is and if it is the jetting.
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