252wheelieking Posted April 8, 2012 Report Share Posted April 8, 2012 (edited) I have rebuilt my engine twice, both times the thrush washer on the big end of the crank shattered on the right side & damage the top end. It appears to be detonation & I have replaced everything with new parts except electrical parts. I brought used electrical parts but they passed all test. Can my aftermarket RM stator be passing the test & be the cause of the detonation. Im very All help is highly appreicated Edited April 8, 2012 by 252wheelieking Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted April 8, 2012 Report Share Posted April 8, 2012 Do you have a timing plate? Did you mod you stock one? Do you know it's detonating? What's your compression? I would send my cases out to get checked if everything else passes. As far as electrical parts causing detonation I don't think so, but shit it can happen Quote Link to comment Share on other sites More sharing options...
BUILDER Posted April 8, 2012 Report Share Posted April 8, 2012 Yes a bad stator can cause detonation. I really do not know if that is your problem or not but my buddies motor I built for him was having issues with it backing plugs out and nothing I tried would fix it. I finally replaced the junk rikcy stator and it has never had a problem since. Quote Link to comment Share on other sites More sharing options...
slothman Posted April 8, 2012 Report Share Posted April 8, 2012 People say that RM stator is a POS, so toss it in the garbage and get a OEM one from Yamaha. Next, you need to look at how much compression you are running, what fuel you are using, and what plug. The BR8ES plug might not be "cold enough" if you are running a high compression motor with low octane gas. If it's detonation you can look at the current plugs and tell instantly if that is the problem. Quote Link to comment Share on other sites More sharing options...
Mustang_Gay81 Posted April 9, 2012 Report Share Posted April 9, 2012 Yes a bad stator can cause detonation. I really do not know if that is your problem or not but my buddies motor I built for him was having issues with it backing plugs out and nothing I tried would fix it. I finally replaced the junk rikcy stator and it has never had a problem since. Im game how is this possible? This doesnt make sense.The only way i could see this possible is if his flywheel has slipped advancing the timing but again that dont make sense again because both times he smoked a motor it was the same issue same side.Somethings not right for sure but i doubt its electrical. But please explain... Quote Link to comment Share on other sites More sharing options...
Coupelx Posted April 9, 2012 Report Share Posted April 9, 2012 Im game how is this possible? This doesnt make sense.The only way i could see this possible is if his flywheel has slipped advancing the timing but again that dont make sense again because both times he smoked a motor it was the same issue same side.Somethings not right for sure but i doubt its electrical. But please explain... the CDI is very dependent on a properly operating stator and flywheel. erratic voltage 'could' made the cdi do things its not supposed to. Quote Link to comment Share on other sites More sharing options...
Mustang_Gay81 Posted April 9, 2012 Report Share Posted April 9, 2012 the CDI is very dependent on a properly operating stator and flywheel. erratic voltage 'could' made the cdi do things its not supposed to. Thats a pretty generic answer.I fully understand the workings of an igition set up but how is the engine going to fire before the piston reaches TDC unless the flywheel has slipped?The cdi is dependent on the two pick up tabs on the flywheel and the pick up coil so again as i said unless his flywheel slipped advancing the ignition i dont see how the ignition can detonate on its own.Detonation comes from high compression ratios and the wrong fuel and overly advancing timing ive never heard of an ignition source being the source of detonation care to elaborate on this? Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted April 9, 2012 Report Share Posted April 9, 2012 Thats a pretty generic answer.I fully understand the workings of an igition set up but how is the engine going to fire before the piston reaches TDC unless the flywheel has slipped?The cdi is dependent on the two pick up tabs on the flywheel and the pick up coil so again as i said unless his flywheel slipped advancing the ignition i dont see how the ignition can detonate on its own.Detonation comes from high compression ratios and the wrong fuel and overly advancing timing ive never heard of an ignition source being the source of detonation care to elaborate on this? I didn't think so either. Like I said I highly doubt its any electrical. But there is an off chance it could be. First I would check your compression. Are you using shit gas? All the other questions I asked too. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted April 9, 2012 Report Share Posted April 9, 2012 Nope. Its my opinion. That's why I said 'could'. Want to know more, I bet the generic site Google.com has more. While the things you named are the most common, dozens of things can cause detonation. Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted April 9, 2012 Author Report Share Posted April 9, 2012 (edited) All I know is: 1st setup I had blow was 18cc domes @ 115 psi (needed to be bored), +6 timing, 100LL 2nd setup was 21cc domes, 150psi (fresh top end) +4 timing, 93 pump gas results was samething thrust washer on right side connecting rod shattered & killed the top end again. So im & wondering should I switch cases & stator? I never had this problem with any other build, only mines with these used cases. This problem occurred when I started using these cases & could be an coincidense. If I switch cases, stator & cylinders shouldnt that kill the problem? Im building my 421 cub now & I can't afford this to happen to my cub, so im trying to avoid this problem. I appreciate all the advice...keep it coming. Edited April 9, 2012 by 252wheelieking Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted April 9, 2012 Report Share Posted April 9, 2012 I'm thinking the cases. Is the spark plug all fucked up from it detonating? And I don't think you should change all those parts. Throwing parts at a problem doesn't fix it. Are the cases a matching set? Did you check for play on the crank? Is you crank true? There's a lot to check because I'm sure you know this by now, this is getting expensive. I would want to know exactly what is causing this. Not just change a bulk of items and hope for the best and find out to late that what you changed didn't fix the problem. Quote Link to comment Share on other sites More sharing options...
bansheesandrider Posted April 9, 2012 Report Share Posted April 9, 2012 All I know is: 1st setup I had blow was 18cc domes @ 115 psi (needed to be bored), +6 timing, 100LL 2nd setup was 21cc domes, 150psi (fresh top end) +4 timing, 93 pump gas results was samething thrust washer on right side connecting rod shattered & killed the top end again. So im & wondering should I switch cases & stator? I never had this problem with any other build, only mines with these used cases. This problem occurred when I started using these cases & could be an coincidense. If I switch cases, stator & cylinders shouldnt that kill the problem? Im building my 421 cub now & I can't afford this to happen to my cub, so im trying to avoid this problem. I appreciate all the advice...keep it coming. Are you sure the problem is not your crank guy? Could the washer be getting damaged when the crank is being assembled and welded? Are the cases a matched set or are they 2 halves from different engines, are you absolutely sure someone else did not mix and match before you got them? Just throwing things out there. In the true sense of the word, your stator can't cause detonation, but it can cause other ignition misfires that would mimick detonation. Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted April 9, 2012 Author Report Share Posted April 9, 2012 I'm thinking the cases. Is the spark plug all fucked up from it detonating? And I don't think you should change all those parts. Throwing parts at a problem doesn't fix it. Are the cases a matching set? Did you check for play on the crank? Is you crank true? There's a lot to check because I'm sure you know this by now, this is getting expensive. I would want to know exactly what is causing this. Not just change a bulk of items and hope for the best and find out to late that what you changed didn't fix the problem. I agree on the cases but it cant be the cranks cause I had Kevin @ HJR look over & true/weld the first crank & Brandon @ Wildcard do the same for the second crank. Both crank thrust washers done the same exact thing. The spark plug on right cylinder looked gray from all the metal in the cylinder I assume, but when i was jetting it both plugs we're the same color. left cylinder plug still look good & ran & it had some small chunks on top of the piston also that i believe came from detonation. My jetting was 34 PJ's: 52 pilots, CEG mid clip, 162 mains temp was between 60*-80* @ 82ft. sea level. Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted April 9, 2012 Author Report Share Posted April 9, 2012 Are you sure the problem is not your crank guy? Could the washer be getting damaged when the crank is being assembled and welded? Are the cases a matched set or are they 2 halves from different engines, are you absolutely sure someone else did not mix and match before you got them? Just throwing things out there. In the true sense of the word, your stator can't cause detonation, but it can cause other ignition misfires that would mimick detonation. I brought two cranks & had them inspected & trued/weld by two different site sponsors....samething happened. I dont think I damaged them, as I have built them plenty of times & it only occurred with these cases on both builds. Cases are a matching set. top & bottom have X9 142 ingraved on them. Im not postive that they didnt mismatch the cases but they have the same number ingraved on them. I appreciate the help as im Thanks for the stator advice as im changing to a stock one for piece of mind. Heard alot of bad things about RM stators. Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted April 9, 2012 Report Share Posted April 9, 2012 Seen issues with some of the CDI boxes around the same year as your machine. Yamaha released a few that had an advanced timing curve Quote Link to comment Share on other sites More sharing options...
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