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Post by sime66 on Aug 7, 2016 11:13:06 GMT
A plug, more than cover, yes; maybe rather than bits of jet or brass, a lead plug like elsewhere in carb - 'tis a tiny hole though, and well needs to be clear.
still pondering............
Could go really flash and have adjustable drilling with interchangeable jets!! - Might be letting the mind wander too much now though.
(sod it; gone on new page; that's going to read funny unless you read end of previous page too chaps).
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Post by vespasco on Aug 7, 2016 16:05:50 GMT
Good tips on filling the hole What maybe even better is a cable adjuster, which could be threaded in but I've a feeling they may be a little too big. The cable end nipples - some people also use these in the fuel line of a pump circuit as a restrictor. I'm just double checking here that you guys are reading rich in all throttle positions. I was worried that we were restricting the fuel flow with smaller idle jets, which would then be too lean in the mid and high range...same with the main jet. Every time I read that a smaller idle jet is going into into a tuned motor I wonder how that can work. But if you guys are running rich enough, then that's fine, I'll accept it! So you are saying it runs too rich, or supplies too much at low rpm, more so on the idle. It's weird as the main jet also restricts flow to the idle. I can only guess it's the effects of pressure pushing/sucking more fuel in through a larger feed hole. I've also often wondered if the si26, being larger diameter, actually slows down the air supply. I realise there should be more air but the velocity is slower? i wonder the same kinda thing with all these pockets on the slides...i know they must add more air and create more turbulence, possibly actually slowing down the air flow? I don't know. I can't get it quite clear in my head right now. That leaves me with what I think is a duff carb but I may have a solution to that! I'm going to try (probably) one of my custardized float bowl tops. I may even try with the top from the si24, as I know thats ok for sure. These drilled out tops also make it run rich, so with my lean carb there maybe a happy compromise!? It's easier than swapping the whole carb too although I can see me faffing around with jets all day. I will no doubt fit the 24mm and then drill MJ feed hole to 1.7, then 1.8mm (maybe). I have the drills on order. Here's your cover Sime...I'll get it posted this week, hopefully tomorrow.
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Post by sime66 on Aug 7, 2016 17:23:54 GMT
There’s a lot to cogitate there, vespasco, requiring an undistracted mind, which I haven’t got at present, so I’ll have a better read later; my minds on wiring at the moment. I don’t think there’s a single, simple answer for all when you get into volumes, velocities, pressures, turbulence – the only thing the same for all of us is the carb body - (and even then, yours has got big holes in it and a wonky bottom). Also, I was initially having trouble getting enough air, so went RamAir, then Vortex, but a smaller volume too – not like either of yours now, either. Another thought re float bowl hole plug though; it’s got to not foul the float, so can’t get too creative – I went off thinking about push-in home-made oversized jets 170, 175, 180……, but nah……… You’re also limited by the diameter of the cast tube between float chamber and jet well for any insert. Going less-wild with opening up channels into and through float and valve all makes sense too, but it ain’t ‘arf getting fiddly with all the trial and error involved, and will be entirely bespoke; you two can have perfection if you like, I’ll be happy somewhere close enough. Careful with cutting-up those float covers too; they’re bloomin’ expensive on Eurocarb (and there’s different ones for Si20 and Si24/26, but I’m investigating that ‘cos I’ve just put a 20 lid on this 26 carb thinking they were the same because they fit, but it might be more complicated than that): www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/carburettor-parts/si-parts/si-24-24-carburettor-top/www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/carburettor-parts/si-parts/si-20-carburettor-top/( Edit: - just read my own links: Si26; needle valve housing = Ø5.2mm. Si20; needle valve housing = Ø4.5mm - I'll measure and check that later). ^^that made me check prices on BS, which reminded me of Pinasco float chamber (also Ø5.2mm): www.beedspeed.com/carburettor-float-chamber-pinasco-upgrade-p-12895.html?osCsid=5pn195n98svfljmmcub8td3pd5which says: "On these covers, the supply hole from the float chamber to the main jet should be drilled out from 1.5mm to 1.8mm (PX177) or 2.0mm (PX200)"....which takes us full-circle, back where we started, and none the wiser! (I'm going back to my wiring 'til someone says something sensible) That slide cover is the one! Well done, thanks; I’ve measured all my Si20s (mainly parts-donors); they’re all 35mm deep slide chamber and covers. I’ve measured my spare-parts Si26 FrankenCarb; it’s a 40mm deep slide chamber. I’m not taking my Si24 off Old Faithful to measure, but I believe that’ll be 40mm too; maybe you or Henri can confirm; you both have Si24s lying around. If you got the drills I linked to, PM me your Paypal and I’ll get them for you if you like in exchange for slide cover (£5?). Those drills look quite chunky, but they do fit in a pin vice, like these: www.ebay.co.uk/itm/2X-Double-Ended-Pin-Drill-Vice-Vise-Model-Jewellery-Making-Repairs-Engineering-/121031591902?hash=item1c2e0b87de:g:lVsAAOxyIPNTdfUTWatching my film of playing with lights in the car park this morning, it appears that the brake light is on constantly, and the tail light works as it should. First thing in the morning I’m going to have another look up the lane without the lens on, so I can see what bulbs doing what at each light setting and with brake pressed and not, but if it’s just brake light constantly on, then that’ll probably be easier to fix – just a jamming switch probably; I’ll get the pedal off, sort it and get back to carb-tweakery if that’s it…….
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Post by sime66 on Aug 8, 2016 5:56:06 GMT
Bright eyed and bushy tailed 5:00am - up the lane, got me facts straight, got back, hoiked it all out and sorted!! (just sticky pedal and/or switch leaving switch pressed when pedal released - got a new switch coming anyway; might use or keep as spare). Anyway, now that's sorted, later today I shall return to technical ponderings on the topic of carb holes.... ............
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Post by pxguru on Aug 8, 2016 13:15:11 GMT
What about just hammering over the hole and re drilling it? Anyone want to give that a try?
It might rely on the length of the hole to drag the flow down, in what is called a laminar principle. in which case this won't work so well. I am thinking this is the easiest way though.
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Post by sime66 on Aug 8, 2016 19:16:03 GMT
... I think these suggestions are getting more outrageous as we each have a go!
I'll whack someone else's carb with a hammer if there's any volunteers!?
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Post by djloone on Aug 8, 2016 23:45:35 GMT
Dont tempt me lol...but keep at it mate...you will get it sussed..n its all gonna be worth it... too the likes of me that has learnt no end keeping up with this and the other threads/contributers on here ...things have moved on so much since 1992 and my last vespa ownership...how the flying funk some of he machines i rode got too rallys and back on baffles me looking back now lol LOON-E
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Post by sime66 on Aug 9, 2016 5:05:52 GMT
Loon-e; referring to our chat yesterday about your carb; the point is page 5 of this thread (Nov 2015 – setting up Si carb from scratch), is where you should refer to, - that’s after you’ve stripped and serviced that 30yr-old carb, that barely had its arse wiped before you re-used it. You can’t skip all the steps and expect trouble-free running, and I like to get where I’m going. Personally I don’t buy into this Scooterboy bravado that braking down is part of the fun, it’s not for me anyway.
Chaps; just had one pondering of little consequence, but thought I’d mention it; little lead-like pellets in the form of fishing shot – various sizes in little packets, cheap on Ebay, might make good little plugs that can be (warmed and?) tapped/pressed in and then drilled. I also have the old Si20 I drilled as a practice before doing my Si26, so that can be a guinea pig, but I still don’t think hammering the hole closed is a good idea; it might collapse the jet well, and edges might crack off and cause a problem.
I also think we might be getting a bit carried away with this well hole subject (apart from trying to rescue vespasco’s 3mm one); perfection, even if achieved on a given day, will only last ‘til the wind changes anyway. For me there has to be some margin that requires jetting tweaks maybe two or three times a year, not every few degrees change of ambient; they’re old Vespas, not racing bikes. I’ll still experiment with spare Si26 sometime because it's interesting to find out, but I’m not going to discard a new carb because the hole is 2mm, rather than 1.8mm, when it works fine with a jetting tweak (if it works fine).
For my jetting, I’m going half-way between last best good safe jetting, and current jetting, then check my plug at different throttle positions (taking care because of high CHT readings - cause of which is not yet certain, and because I’m suspicious of the Pilot I ended up with before). After that, there are two further tweaks to get back to last best good safe. Middle ground is 45/160, 135, BE3+1, AC160, #4, 2mm drill; that’s my next jetting tweak. It’s cooler in the mornings now too, so that’s another reason for a bit of caution; I’ll be back to crossing the Moors in the cold, dark mornings before the months out.....
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Post by sime66 on Aug 9, 2016 9:28:06 GMT
Cover arrived already, vespasco, thanks (you really should sign your artwork though; get more for it on Ebay then). I sent Co-Pilot Service Number INC48-160 to see you yesterday evening; he’s 1st Class – Chocks away!!
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Post by vespasco on Aug 9, 2016 18:09:07 GMT
Ah yeh! I think I was on the phone, doodling away, when I had your envelope in front of me. I was inspired by your seat And did someone mention hammering carbs? I've used a hammer on a carb before! hahaha But I'm not sure this hole would be do-able Sorry for the poor pic but you can just see how much I drilled away at the bottom of the MJ feed hole, hoping to use a bit more of the float chamber. I think it was a stupid move and probably played havoc with the fuel levels in the carb. Another carb modification, Another crap photo I may actually fit this again, just for fun. It has drilled out float feed hole (i think to 3mm but will confirm next time I'm tinkering). Whatever it was I think it was too much. There's also another mod. to aid fuel flow in the carb that I've seen mentioned a few times, maybe on here and that's drilling more holes, if required, to the outlet holes of the needle housing on the float bowl top. Some tops only have 1 or 2 holes. I may have even drilled these out too. I don't recall and all my notes on this are packed away with all my other manuals etc. (Except my small The Vespa Notebook) I'll put Co-Pilot INC48/160 to work asap but I heard he's an idle barsteward
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Post by sime66 on Aug 9, 2016 19:53:58 GMT
Not a Jackhammer though! – Were you trying to round the edges to make it flow from the bowl better? It does need a sort-out doesn’t it. I think you were on your jolly jaunt when I did mine, but there was less mining involved; I had those little micro drills and tiny files:
I’ve put my box of carb bits away now, except for the one I’m working on, but I also noticed some of my tops had extra holes like you show, but they weren’t on bigger carbs, and look original; I’ll make a note of the different numbers and sizes of holes I’ve got sometime. I was also thinking about what mods I’m going to do on this Si26 float cover, and I think I’ll do the same as I did before (pic above) because it isn’t flow the into bowl that’s the issue for me here, it’s flow from bowl to MJ well. I know you had fuel starvation issues though, but if mine was OK with those mods, it’ll be OK with smaller jet well holes too.
Yours is going to need a proper-job to get it sorted; surely you’re going to need to fill it and redrill? I was thinking more about this earlier; if you filled the bottom of the float-bowl to Jet-well channel with a tiny plug (like blutack, plasticine, or something that can be pushed in to seal it temporarily and fished/drilled/blown out after, then you’ve got a funnel with a blank-end, which you could fill; maybe even pour lead into - we used to melt lead to make weights, so that’s easy enough to do. Then you could get it tidy inside the bowl, and as long as you had the location and angle of the hole measured beforehand, you could re-drill it to the right, or starting size. I think that’s what I’m going to do with the Si20 I drilled when I shouldn’t have:
I’m sure we’ll come up with something worth trying anyway……
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Post by pxguru on Aug 10, 2016 8:33:09 GMT
Any thoughts about chemical metal? It seems to not fall off the engine cases when reshaping transfer ports.
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Post by sime66 on Aug 10, 2016 9:02:34 GMT
Pros and Cons: Chemical metal is easier to work with, sticky to aluminium, easy to sand a drill, which makes a powder so should be easy to flush, but will such a small lining of (brittle when hard) material hold up under vibration, or flake off and block MJ? Not blocking MJ is pretty crucial to any solution working. It is fine in petrol too. Lead will pour into the hole (probably better than chemical metal, which would need careful filling, so as to fill channel, but not to push bung through), but not pleasant to play with molten, and is soft to drill (too soft for accurate drilling?). I’d say less likely to flake because it remains fairly soft. It’s OK in petrol; they use it as plugs in the carb already. (And I’ve just nicked a wheel balancing weight off a neighbour’s car, so have a ready supply). Dunno; which do you think would be best?
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Post by pxguru on Aug 10, 2016 11:55:29 GMT
Using chemical metal I think would need a bigger hole drilled first. And nice and rough with plenty to key on to. Could leave a small dollop in the float bowl too. I don't think it would ever break up and block the jet but falling out would be the main concern.
The ony problem with lead is that it might run in too far and block everything.
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Post by sime66 on Aug 10, 2016 12:09:45 GMT
Putting in a small bung (magenta) before pouring lead (yellow) to prevent it going into well was my solution to that, as shown on my little sketch previously posted above. Here’s another one I prepared earlier….. I thought about opening the hole to enable more material to be left after drilling; ..…so now’s a good time to share this beauty; it was on FaceBook a while back as a way of opening up jet well (no offence intended towards originator, BTW). Certainly wouldn’t have a problem with swarf in the dirt pocket! But would play havoc with your laminar flow! I think they must be suggesting that void under carb is part of fuel route – eek! (Or, I suspect, just a bit of over-exuberant mining - ring any bells, anyone? - , expained-away as planned for). (warning, contains bodgery):
Anyway, that’s not the point of posting photo: I actually dug it out because it occurred to me that opening hole up a bit before filling might help, but you can see from photo how little aluminium wall there is to play with in the channel; not much room for error with position of hole or angle either. (I'll measure the OD of channel later, but you'll take the point * O.D. well = 6mm, hard to be certain about channel, but not bigger).
I think I favour the poured-lead option at the moment.
Edit: (as I was adding in well dims*....)
...Just a last afterthought for now; I've got some O.D.3mm copper tube (I.D.2mm), - I got it for my thermistor tinkerings -, which vespasco might be able to slip (glue? tap if tight?) into his 3mm hole to make it 2mm again - I'll send you a bit to try if you like, vespasco; you could swage the end or make a little foot to stop pit falling in:
(All right, it's a long-shot, but at least I didn't suggest the hammer)
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Post by vespasco on Aug 10, 2016 15:01:41 GMT
haha. I also thought of a small tube like 'something' that you'd find around the house/shed. But failed to come up with anything. That small copper tube sounds well do-able and would be the easiest route by far...and safest...its too big to fall out and do damage. I'll keep searching on my travels for something similar, ali or brass ideally. And the bonus is, I can fit it with a hammer hahaha That carb above, I think I would try lead, or something you could screw into the hole, like a brass bolt, (air mix screw?) or use 'something' that you'd find around the house/shed. hahaha
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Post by sime66 on Aug 10, 2016 15:29:11 GMT
The tube option grew on me after I posted as well, but if you don’t want copper, you’ll have to get your own! 3mm aluminium or brass (metric) = I.D. 2.1mm; chaps who build model steam stuff use it: maccmodels.co.uk/materials-metal/aluminum-sections/aluminum-tubes/aluminium-k-s-tube-metric/3mm-dia-aluminium-tube-12-long.htmlmaccmodels.co.uk/materials-metal/brass-sections/brass-tube/brass-k-s-tube-metric.htmlThere’s imperial too, but I’ll be faffed if I’m playing with thousands of inch wall thicknesses to work out metric I.D. for imperial pipe – what a shἰt system that is for the Luddites who won’t go metric! Anyway, that’s for your carb, not for playing with our currently 2mm drilled carbs where I reckon the lead option is currently favourite. That last photo of carb with holes in bottom of well is not mine (if I’d done that I’d have binned it, not photographed it); it was on Facebook a few months ago, I posted it above for fun, and to show how little wall thickness there is to play with if you're trying to open the tube for chemical metal. Mine is shown in the first reply to your photos of your aluminium-mining project last night. Mine is 2mm and spot-on tidy, and staying as it is because I have another Si26 to drill smaller now, though I do also have a drilled Si20 that I might try some lead in sometime. I reckon we've salvaged your Si26 now though.
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Post by vespasco on Aug 10, 2016 16:29:23 GMT
Oh. I thought it was an ebay thing. Glad it's not yours. I'll find something for my old si26 but I'll keep that small pipe in mind. That's the best way. Something with a smaller diameter even better, or even solid would be ok (aluminium floorboard rivet?) but that may just salvage my donor carb I tried a search for an imperial equivalent of around 1.8mm... wish I hadn't. Drives me nuts sometimes too.
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Post by sime66 on Aug 10, 2016 16:52:12 GMT
Aluminium rivets! (Got fousands of 'em; all lengths and thicknesses; cut the wire out perfick size:
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Post by pxguru on Aug 12, 2016 6:46:23 GMT
Rivet would fit perfect once drilled out some more. Do you think it would bang in ok or need some glue?
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Post by sime66 on Aug 12, 2016 7:26:13 GMT
Dunno; my Si26 carbs are 1.6mm(ish – not checked) and 2mm at present, and I’m not sure I’d want to drill the 2mm to 3mm to fit a rivet; so I’ll be playing with the 1.6mm one instead, which just needs opening to 1.7mm to start with. However I think vespasco would be the man to have a go with rivets because he’s already 3mm. It did occur to me that it might be possible to make a number 3mm OD rivets, with ID 1.7, 1.8 and 1.9mm, and go up in size by swapping them – as long as they could be removed again, but I’m not sure that’s a good plan – AND I broke my 1.8mm drill bit last night ‘cos I got it stuck inside the rivet while I was playing with making a set of different IDs. After that, I think it would be better if the carb hole was tight and the rivet tapped in (as long as it doesn't crumple?) and drilled-out in situ afterwards – though care needed not to break a drill bit off in the carb! I think it would be easier to drill-out a hollow rivet than drill a solid rivet and keep it true. I think we need a volunteer to have a play.........(happy to send some rivets to either of you you've if none to hand; I'm going out at 11:30).
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Post by pxguru on Aug 12, 2016 16:24:07 GMT
Whatever goes in there, it should be drilled out after. I think aluminium is better as it won't move with expansion. I am in no hurry to do my tourer. I think I will experiment on an old 24/24 (I have a few), if it does turn out to be ok on the 24/24 (as expected), it could very well stay like that for quite a while. Been fiddling with the Polossi today. The carb on that is a different kind of complicated. Here's one just like mine. He must be on a private road and looks like he doesn't even have his head down
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Post by sime66 on Aug 12, 2016 18:49:39 GMT
Is this someone we know……..? 15th(?) August 2016?? Hmmm. Sounds the business doesn’t it. Love the 4th climbing on forever like my 3rd does, but like I’ve not yet cracked for 4th. I’ve tried to catch the peak in 3rd and 4th, but it’s quite tricky with that analogue rev counter, and no GPS, just conventional speedo in MPH: 3rd goes to 63mph (not GPS) and around 7750 (7¾ thousand estimate from freezing film) – probably quicker to get there though, but it’s hard to judge that; I’ll get the WAV to see how long it is….. 4th goes to 83mph (not GPS) and around 7250 (7¼ thousand estimate from freezing film). I think I remember you having 81mph GPS (just checked – Jan 6th, page 13), and your tag says 8,700rpm, so this isn’t that close to yours is it? I wonder if the sound recording is good enough to extract the WAV and let Dyno have a look at it to get revs etc…………. 3rd gear WAV (16 seconds), good sound – my rpm app says 7670:drive.google.com/file/d/0Bymw3paxDl18VUJFZG51ZjB2UHM/view?usp=sharing4th gear WAV (29 seconds), wobbly sound – my rpm app can’t pick it up clearly enough:drive.google.com/file/d/0Bymw3paxDl18S3hTdDctdmlOYUU/view?usp=sharing(Head down and filming speedo and stuff is quite tricky; I’ve been thinking about that – rigging camera on scoot, rather than helmet). MOT Tuesday, and my foot’s improving (still no boots on though); anyway, after Tuesday, I’ll get back to breaking the scoot again…….
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Post by vespasco on Aug 12, 2016 19:01:10 GMT
Hahaha C'mon. Fess up, that was kmph. Holy crap. That pulled with ease upto 80!
I'll be tackling the carb next week/end hopefully. I want to get the vespa running a little better first before i start swapping carbs. But I surely must have some rivets to tap in the hole with a hammer
I did get a chance to try my custardized float bowl top.... Drilled out to 3mm but not all the way through, so the needle still seals.
I also measured a si24... MJ feedhole was 1.6mm or less. The other si26 I have is 1.7mm from new.
*BGM faster flow is 1.8mm With a drilled out cosa top They also leave the venturi at 25mm as if it was 26mm it would leave very little tolerance for wear on the slide. Pinasco bore their si carbs out to a proper 26mm and the MJ feedhole to 2mm.
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Post by pxguru on Aug 13, 2016 8:44:21 GMT
You know 7670 rpm in 3rd gear is 61mph on a P200 gearbox. Speedo looks like its been set up properly. I have dropped the packer a bit on mine only goes to 8500 in 3rd now but usually I just take it to near 7500.
To get the atomiser working correctly, what I suggest is to start at 1.7mm and a 155MJ and keep drilling it 0.1mm bigger until the MJ floods out and has to be smaller, ending up something like 145MJ.
Pinasco might do something else too to make the atomiser work properly. There might be something we are missing.
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Post by sime66 on Aug 13, 2016 11:13:48 GMT
If this was indeed someone we know, I’d have a proper play with the WAVs, dynos and gear tables, but then if the someone we know is the someone we know I have in mind, then he wasn’t going full beans anyway, so either way; that’s probably enough number analysis from the film. Great scoot and filming though, but not HD; what’s the camera? I think 63mph indicated, and 61mph from gear tables would both be higher than actual – for reasons previously discussed - and GPS would be lower than both of those….. So speedo being out about 5% would be about right, ie 59.9mph. Is it the worm-drive or magnet SIP speedo input? (For 23x65; 12,13,17,21 & 57,42,38,35, with 1320 tyre, I’m getting 7670 in 3rd = 60.2mph, and 7250 in 4th = 76.3mph); 95% of 83 = 78.8mph, so thereabouts from best-guessing rev counter from film and estimating speedo error. My best GPS in 3rd was 101kph = 63mph; we all get about the same max in 3rd, but only The Beast has it recorded on GPS on film! (And that’s all it’ll do, and I did blow it up shortly afterwards trying to get 9000rpm). My best GPS in 4th was 116kph = 72mph – my 4th is a bit of a girl, but good enough for me ‘cos I am too! I like the plan you suggest to get the float bowl-to-MJ well hole right gradually to get the MJ sensible to get the atomiser working right (with AC160, BE3), but I’m in no hurry right now; I still want to do last good jetting first to see what the temps show now, to try to get to the bottom of why my CHT is high*, or to finally and fully convince myself to ignore it; I’m still wary of thrashing it when CHT is high. I also want to be sure my Pilot is right as first job because CHT had some bearing in why I went so lean, and I want to redo it properly. I still don’t think we’ll all end up with the same size hole either – for various reasons raised above (different cylinder capacities, different timings, different porting, different exhausts, my vortex). I want to compare my float covers with vespasco’s dimensions and info, posted last night too. I’m sure we’re missing something; I am anyway, ‘cos I’ve just spent a year running in then playing with this carb; I’m supposed to be tip-top and moving on to Autumn planned maintenance soon! *Two points I'd like opinions on re; high CHT temp please chaps: 1) Could my decreased squish actually be giving me genuinely higher cylinder temps (by 15-20°C?) 2) Could my worn rings be reducing lubrication up top of cylinder and be giving me genuinely higher cylinder temps (by 15-20°C?) I'm going to be far happier thrashing mine again when I'm sure the CHT readings I'm getting now are bogus, or by finding cause and fixing it. I know my plug is OK, but there are causes of high temps other than lean mix. It's bugging me.
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Post by vespasco on Aug 13, 2016 14:48:30 GMT
Fuel
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Post by pxguru on Aug 14, 2016 13:32:07 GMT
I don't think there is anything wrong with your engine. Rings, compression, head, all fine. I think you should now put the jetting back as it was but on a 135MJ. I think you will be the same as my tourer then. If I had a Vortex I think mine would be better at low down rpm too. You know the SIP speedos can be adjusted by the user. There is no need for significant error. Mine is +/- 1 mph from GPS, as I have adjusted it. And they just count pulses so are linear too. If you consider the beast is about 7mph quicker than a standard P200 or T5 and its not even tuned for speed, This Polossi is 10mph quicker than that. Really quite something. Why you think the scooterhelp gear speeds are no good? They seem close enough to me. I think this SIP speedo is tuned the other way. There is no way that is 94 mph! Is a very quick scooter but not that quick. can you hear how badly the carb is adjusted? And them building that engine is like watching monkeys make tea
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Post by sime66 on Aug 14, 2016 16:10:45 GMT
None of this below is crucial, but it’s all interesting to me, so I’ll go through each point you make. I think I recall you saying worn rings might hinder lubrication getting up the barrel and increase heat, and my ring-gaps were quite large; a point I made when I reused them rather than using the new ones. It’s just been on my mind when I’ve been trying to suss out why my CHT is high now. I put the top-end back on and fixed the CHT at the same time, one or other is different, and there is a reason; I’d like to be sure which has changed before changing more stuff, (especially jetting leaner), but I’m also fairly sure nothing is wrong with the engine; just trying to discount possibilities before they potentially become problems if not considered. Yes the jetting is going back as it was, I also agree 135MJ; my only doubt is Pilot, so may try one size up first. I wrote it down a few days ago, so I’ll check quickly; I was going: 45/160, 135, BE3+1, AC160, #4 (I might end up back at 42/160, but I want to try 45/160 first; I will probably go back to BE3+2, but I want to try BE3+1 first – those temporary, slight deviations from before because I want to check my plug at Idle, Progression and that tricky (3000rpm-ish?) first bit of Atomiser, because I can’t trust my CHT gauge at the moment). I want to know that’s right before I settle on (135?)MJ. It’ll only take an extra half-hour to do it in a few stages on a cool morning to be sure, aiming for the 42/160, 135, BE3+2, AC160, #4 I had before. That’s with the 2mm drilled carb still; I may go on to playing with carb drilling, starting with 1.7mm - afterwards. How much I get done really depends on what sort of Autumn we have, and which of the planned jobs I try to get done before the weather becomes too bad to mess around in the garden (not for me, but for paint etc.) – unless I find an alternative venue for my tinkerings. I have quite a lot I’d like to get done before Spring; some of it is more important than others. I didn’t know SIP speedos were adjustable (for accuracy, or just by changing wheel diameter?), so they work like my pedal-bike then; not a cog, but a magnetic pulse and a wheel diameter. Your Palossi has recorded 8mph (GPS) higher than my highest (81-73mph - both GPS); I’m not sure that film someone posted of theirs shows 10mph higher (83mph - speedo) though; I think that 83mph is high; the corresponding revs are too low in any case; it’d have to be 7900 in 4th, without losses*. (I’ll say why I think that as I answer your other points – but not in too much detail, as it isn’t someone we know). Only GPS is gospel, or as close to it as we’re going to get; didn’t we agree that? I don’t think Scooterhelp gear speeds are no good; I don’t use them now that I’ve done my own, (which I do know are accurate; it’s simple maths and a measured tyre), so I haven’t compared the two for a while (working out how Scooterhelp did theirs was how I sorted mine out; the principle is exactly the same). I do think that speed, obtained from rpm using any of these gear tables/calculators, will be a theoretical speed that will be higher than actual achieved (due to losses like clutch and road-to-tyre*). In all cases, in the admittedly very short time I’ve been doing dynos, or more recently comparing recorded revs with recorded GPS speed, the actual GPS speed achieved has always been lower than that calculated from recorded revs and reference to gear tables/calculators. I’ve made the point several times in the past that actual GPS recorded is less than what should theoretically be achieved from revs; I’ve asked why, and made my own conclusions where the losses* are, which haven’t been challenged. *The rotation of the crank - calculated through, with gear ratios and tyre size - is not identical to road speed. (Nor is the rotation of the front wheel, which slides, expands and deforms) (revs - of crank or wheel, are not identical to GPS speed). Conclusions:I was just picking brains about my CHT; if I don’t find the answer, over time I will learn to trust my plug, but without CHT my progress will be slower because I will be being more careful. (My CHT might always have been 15-20ºC out before and I might have been 165ºC when I thought I was 150ºC – you said yourself that you didn’t think I’d done all the wear on the barrel in one seize – again, just thinking aloud; it doesn’t need a reply). I would like to explain the error, or be sure I can disregard it, without which I will proceed with caution. It occurred to me that there might be a mechanical explanation that was not related to heat of combustion itself, so might not show on the plug; it was an afterthought tacked on to my previous post about the fun bit – just chewing it over with you chaps that know stuff. My scooter is still running perfectly well in all conditions; rev-range, hot/cold, starting etc, (not getting top revs, but that’s safe jetting and because I’m being careful riding ‘cos of CHT - 48/160, 135, BE3, AC160, #4 now - not so far off; Pilot and Atomiser), and the performance when set up well has already been proved; I don’t feel any urgency to getting it so close to the edge again – because it doesn’t matter that much to me, and because it is guaranteed to be getting much colder in the next months; it can be improved now for sure, but it isn’t crucial. This is all curiosity and interest, not the need to change anything. Other than my foot for the last fortnight, I’m still out and enjoying it loads. Having said that, I do have planned jetting changes for later in the week, after MOT on Tuesday, or next weekend. The speed, gear table/speedo/dyno/gps conversation now, likewise is for interest, and maybe to reach some agreements on our thinking, but it’s just conversation, not critical to what any of us is doing. I know for pretty certain, quite accurately what mine does when jetted close to optimum, but I’m not competing with either of you two at all, just comparing for interest and a bit of fun. I'd be better comparing with your Tourer anyway. The more of us that shares accurate data, the better we’ll understand what we’re looking at – or if we at least do our own consistently, comparison for our own improvements is equally valid, but not so much with each other, but it doesn’t really matter; it’s just interesting. I had a quick look at that video; I need to re-watch it a few times to pick up on all your points. Özant Emil isn’t going to make old bones though is he - at whatever speed the Jackanory speedo is saying. (I've just posted that, and it's too long, so I can't even be bothered to read it to check it now, so I doubt anyone else will wade through it; must try to keep it brief).
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Post by pxguru on Aug 15, 2016 4:20:43 GMT
For our needs, anything within plus or minus one mph is close enough. You might think GPS is exact but that has a tolerance too. Generally accepted is that a commercially made sat nav like a TomTom is plus or minus 0.5 mph depending on the day and other variables and a smart phone app will be a little less accurate, usually back to plus or minus 1 mph. Easy to get hung up on the details and miss the big picture.
Can you check the rpm of that Özant Emil video and see what the speed really is. Will have to just guess that it is a P200 gearbox.
Another thing to consider with the lower pilot jet, is that the extended inlet timing makes it run richer, so will need a weaker pilot jet to compensate. How far over is your new CHT sensor?
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