madman Posted July 27, 2006 Report Share Posted July 27, 2006 Hi all Having a bit of trouble with my lads sherco 50 it starts fine but when it gets hot it runs badly sounds like a misfire. Ive stripped the carb and cleaned also cleaned the reeds.ive checked the wiring for good contacts and put a different spark plug in. how do I: 1/ test the stator 2/ remove the flywheel to inspect the stator or replace the stator 3/ test the CDI unit 4/ test the compression i can borrow a four stroke compression tester will this work on the 2 stroke. What compression should i epect has anyone got any ideas what else may cause the running issues. also it gets hard to start when it cuts out. many Thanks Phil Quote Link to comment Share on other sites More sharing options...
alan bechard Posted July 27, 2006 Report Share Posted July 27, 2006 (edited) I know you said you did it, but I would go back through the basics, new plug, checking connections, clean fuel, clean filters, tank vent clear, good grounds etc. first. (maybe again) I have heard of one that had a bad electrical part in it and I do not remember which it was. The troubleshooting consisted of swapping the parts until they determined which was bad. The flywheel pulls with a little puller that looks like a plate if I remember right. I think I got mine from PoliniUSA, It is a pretty universal one that all the 50's used if I remember right and my buddy that races 50's has it at the Youth Nationals right now for a week or so. I may go to Lorretta's and see him, and I will look at it while there to refresh my memory. But my basic memory was flat plate kind of like a small harmonic balancer puller. As to compression, I never ran a test on one. You should be able to feel if it is "normal" or not and it sounds like this is something that just changed greatly so I would suspect the compression fault to be something constant (broken ring say) rather then a gradual loss of compression. If I was hunting, I would bet plug (I would put in another new different one to test) or the plug lead. Little cap on plug or something along those lines. You can also get some more help here http://www.poliniusa.com/forum/ Some of the stuff there may not be relevant, but most will. The guys in Florida that were / are the US importers for Polini were also always more then helpful. I do not know if it has sold or what but what I am seeing are guys in CA, so I am not sure. Let us know what you find. I will alert Chitlen Charlie to this thread, he had the one with the electric problem and get him to chime in. Edited July 27, 2006 by Alan Bechard Quote Link to comment Share on other sites More sharing options...
madman Posted July 27, 2006 Author Report Share Posted July 27, 2006 cheers alan ill buy a new plug tomorrow and put that in. ive cleaned the fuel tank filters and carb a couple of times i was suprised how much water was in the tank the first time. The bikes not been running as it should for the last couple of weekends each time i find somthing and think ive cured it.run it in the yard and it runs graet as soon as it gets a good bit of throttle it stalls and is hard to start i suspect somthing electrical. ill go right through it again. ill keep you informed Quote Link to comment Share on other sites More sharing options...
alan bechard Posted July 27, 2006 Report Share Posted July 27, 2006 http://www.poliniusa.com/forum/viewtopic.php?t=461 Quote Link to comment Share on other sites More sharing options...
madman Posted July 27, 2006 Author Report Share Posted July 27, 2006 Thanks alan i dont think the compression is a problem ive removed the plug and put my thumb over the hole and it blows my thumb off when the engine is kicked but ill borrow a guage to confirm this Quote Link to comment Share on other sites More sharing options...
charliechitlins Posted July 28, 2006 Report Share Posted July 28, 2006 Our 50 began to be hard to start and would miss at high RPM (cut out, actually...felt like a rev limiter). Then, the problem began to creep lower in the RPM range. The old "start swapping parts until the problem goes away" revealed that the coil was the problem. Quote Link to comment Share on other sites More sharing options...
madman Posted August 1, 2006 Author Report Share Posted August 1, 2006 tested compression which was 110 psi so not too bad IMO. tried a new plug still ran like a three legged dog. i've ordered a new stator and coil so hopefully that will cure it. I'll let you know how i get on Quote Link to comment Share on other sites More sharing options...
alan bechard Posted August 2, 2006 Report Share Posted August 2, 2006 (edited) Sounds like it, hope that sorts it out for you. Maybe you could read your old and new stuff while you have it side by side and we could start to develop a troubleshooting baseline on that? Edited August 2, 2006 by Alan Bechard Quote Link to comment Share on other sites More sharing options...
madman Posted August 4, 2006 Author Report Share Posted August 4, 2006 the stator has changed since my origional so the readings dont compare but the coil is the same and the readings between the sparkplug electrode and the stator pickup were 0 ohm on the new and 0.76 ohm on the old one. the spark on the new one is nough to jump from the plug cap to earth wheras the old setup would just manage the spark plug in open air. Quote Link to comment Share on other sites More sharing options...
madman Posted August 5, 2006 Author Report Share Posted August 5, 2006 had the bike running today in the garden and it started ok but seemed to be running hotter. the ammount of power the thing has found has put a smile on my lads face again. he ran it round for 10 - 15 minutes and came to stop it but the cut out would not work(it did work when i started it a few times previously). so i gets a rag and pulls the spark plug cap off (get a good old jolt up the arm in the process) and believe it or not the damn thing still ran. Turns off the fuel and it cuts after a couple of minutes. the motor was very hot which ive not witnessed before. Im therfore thinking the ignition is too far advanced and start wondering if ive put the stator on the right way? the stator fits in one of 2 positions and ive switched it back to the first way i fitted it which according to a diagram ive since found is the correct way. So the bike has been ridden with the ignition out by 180 deg's would this cause the overheating? im suprised it ran at all unless it makes no difference. Maybe its running hot because it needs a bigger jet (50 currently) now the spark is so much better. could an engine get that hot that it doesnt need the spark plug to run? its all got me wondering. the timing canot be altered on the new stator as its fixed but there is a couple of degrees by just turning it a tad before tightening. there is also a slight knocking sound from the engine is this pre ignition or something Quote Link to comment Share on other sites More sharing options...
alan bechard Posted August 5, 2006 Report Share Posted August 5, 2006 (edited) I am missing something in the equation here, I actually came on to ask if it sorted it, but you must have been out trying it. Next time you go to kill one, take that same rag and plug the exhuast, that should bring it too it's knees quite quickly. Sometimes just choking them does the trick as well. I cannot imagine getting my hand in there to pull the plug cap. Did you have the plug cap well away from the plug? And it still ran? Idled? Have never seen a "runaway" that was not screaming, and that is a handfull on a centrifigul clutch bike. I have seen them run away without ignition but they were always real hot and then they were running like an old model airplane with a "glow Plug" in the head. Some "hot spot" that continued to provide ignition for the motor. If it was mine, I would be curious enough to pull the head and look. The one's I have seen were also usually running "tapped" like a stuck throttle cable or slide or whatnot and getting plenty of fuel. As to being 180 out I would want to sit and stare and think at that one quite a bit. I may be missing something but would that not cause it to fire on the bottom of the stroke?????? I keep coming back to different winding's or wires or something. I feel certain there is some portion of this equation I am missing. http://en.wikipedia.org/wiki/Two-stroke_cycle I have never had the stators out, how many winding's and wires are there? Edited August 5, 2006 by Alan Bechard Quote Link to comment Share on other sites More sharing options...
madman Posted August 5, 2006 Author Report Share Posted August 5, 2006 Hi Alan yup its got me a bit baffled too. The plug cap was a good couple of inches from the plug but it was like the whole bike was live! my son got a belt from the handle bar. The engine was real hot. The new stator has 4 coils and im thinking that it may well run in either of 2 positions as obviously the bike would not fire at the bottom of the stroke and deffo not with the ammount of power it had it is the quickest ive seen this bike run in a while. the bike was ticking over perfectly and accelerated rapidly. Good point about blocking the exhaust though (its a method i use on our model cars) i just wasnt thinking quickly. bike maybe lean becxause of an air leak. ill check that. but im a bit stumped Quote Link to comment Share on other sites More sharing options...
alan bechard Posted August 5, 2006 Report Share Posted August 5, 2006 How many coils on the old one and how many wire's? Just curious now as I can probably offer no help, but would be interested to know the outcome or see pictures. If needed I can get my BIL to look at his. He has an 04 and to the best of my knowledge they did not change. I know he does not have the stuff to pull the flywheel though so it may not be much help. Good luck, got to think it is something straight forward when it get's sorted out. flywheel key? I think I would peer at the top end if it was mine to see if it was hot enough to damage something, or if there are any clumps of stuff hanging about that could hold heat and act like a glow plug.... Probably the electrode tip though I would imagine, but do not really know. Did it idle at the period without the plug connected? Quote Link to comment Share on other sites More sharing options...
madman Posted August 6, 2006 Author Report Share Posted August 6, 2006 (edited) It idled fine the old stator had one coil and picked its earth up through the engine and frameand therfore useda single wire. The new stator has 4 coils and 2 wires one has a tag on that connects to the coil earthing connection the other goes on the coil +ve feed. Just on another note ive also changed the engine oil seals as it was smoking a bit must have been getting a little transmision oil sucked in. Maybe that helped cool it too. Smoke is OK now A 50 jet is not that big maybe i need to go up a size. Might give it a try. What else could make it overheat. Small yard on and off the power, thrashing it ,clutch getting hot. Maybe. Im using the same oil mix fully synthetic 125ml/oil to 5 Litres of fuel. Does anyone else running one of these know what size main (only) jet it uses ? Edited August 6, 2006 by madman Quote Link to comment Share on other sites More sharing options...
madman Posted August 9, 2006 Author Report Share Posted August 9, 2006 ok ive checked the timing with a strobe and all seems ok with the timing the carb is jetted with a 60 main not a 50 as i suspected the spark at the plug is immense compared to the old setup ive discovered a leak on the inlet manifold i ran the engine up and sprayed some cleaner at the manifold which stalled the engine so ive sorted that problem when starting the bike there is a lot more resistance at the foot maybe because the spark is better dunno! still got a bit of a knock which comes and goes when bike is idling is it cos its running weak? im gonna get some jets and have a swap ps took head off all seams ok maybe air leak was weakening mixture enough to cook the motor Quote Link to comment Share on other sites More sharing options...
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