trex banshee Posted March 28, 2011 Report Share Posted March 28, 2011 (edited) I am in need of some help on a bike of ours. it has been put together for atleast 3 seasons now with no issue for the first two years. Last year it started breaking the right spark plug. The right cylinder would drop so we would pull the plug and there is basically nothing left! you can imagine what that leads to, chewed up piston and dome. So I pulled it apart and went through everything double checking it all. Could not find any obvious air leaks or problems. The color of the top of the piston looked great and so did the color of the plug, what was left. So put it all back together, needless to say it did the same thing, twice... This bike is a 350 stock cylinder drag ported on alcohol with 35mm carbs. stock coil and cdi running just the standard b8es ngk plugs. base timing is set at 10. We have replaced the cdi thinking it went south and sparking the plug at the incorrect time, that changed nothing. The jetting has been the same on this bike for 3 years now and the carbs used to be on my bike with no issue for a few years also. we have also turned the timing all the way down to 4 thinking we were getting into detonation but that did not cure the issue. Is this a sudden shortage of fuel and excessive air causing this or is it on the electrical side? It takes about 3 good 300 foot passes for it to do this, but at the same time leaving everything other than the plug, piston, and dome looking perfect. Thanks for the help, Thomas Edited March 28, 2011 by trex banshee Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted March 28, 2011 Report Share Posted March 28, 2011 Shouldnt you be running 9's on methanol. I dont have any experiance running methanol but I do know that they run B9ES or BR9ES plugs. What are your compression numbers? What is the squish? Quote Link to comment Share on other sites More sharing options...
Mike Z Posted March 28, 2011 Report Share Posted March 28, 2011 Based on the information you gave, the motor is definitely detonating because that is the only thing that will shatter a plug. If it is something that has just developed over the years, then more then likely the problem is an air leak. If you blipped the throttle, would the rpms comes right down or do they come down slow? The first test I would do it to see if there is an air leak. This is very east to do with just a few parts. First you will have to remove the pipes and carbs. If you have a stock bumper, take the rubber ends off and bumper, get a hose clamp that will fit over it and then put those ends on the exhaust flanges making sure to tighten down the hose clamps. Now go to your local hardware store and by a set of electrical pipe ends that are close to 28mm or 1 1/8" inch. You can also use a PVC end that also has an OD of 28mm or 1 1/8". Now buy a schrader tire valve(the kind that have nuts on both ends and then drill a hole in one of the caps you bought to stick in the intakes. No matter what size you choose. Now make a hole to you can screw the. Now normal case pressure is between 4-7 pounds, this is not really important but it is good to use it as a guideline so you don't pump in to much air when you check to see if the motor is sealed. Now that you have the intake and exhaust sealed, pump up the cases with about 6lbs of air. Now wait for at least 15 minutes and then check the pressure again. If it is still at 6lbs, then you have no leak. If it loses any air within the 15 minutes, then you have an air leak and will need to find it. The best way to find the leak is to remove anything that covers seals(side covers, flywheel and the area where the to case half's meet) then pump it back up to about 6lbs and spray with soapy water and you will find leak by looking for spots that soap bubbles are forming. Now that you have found the leak, you will need to fix it and that depends on what is leaking. If there is no leak, then my second guess would be that the gas you are using is bad, probably from sitting over time. It may also have low octane and the motor requires that higher octane fuel be used. If octane is the problem then the fix is the easiest to fix. Just by better gas like some race fuel. If your motor is not set up with that much compression, you can also get away with a 50/50 mix of regular. If you do these two tests and nothing changes, then there must be a more serious problem. Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted March 28, 2011 Report Share Posted March 28, 2011 Did you try swapping carbs side to side. If problem moves, it's in the carbs...otherwise sounds like a clutch side air leak. Is your basket sealed at the shaft? Quote Link to comment Share on other sites More sharing options...
trex banshee Posted March 28, 2011 Author Report Share Posted March 28, 2011 thanks for the replys guys. No i have not swapped carbs, also if you just start it up it idles fine, you can set there and dry rap it with no issue at all it never runs away due to an excessive lean issue. The fuel is alcohol so the octane is not the issue. The compression on the bike was i believe right at 170 with .048 squish. As far as the particular plug ive always ran 8's on my other bike and its been going strong for atleast 5 years no issue whatsoever. When we get another piston and dome bought im definitly going to the hardware store to build a leak down tester. the only way i have been able to prove this bike had no leaks was with starting fluid. Any other ideas?? Anyone ever had an issue with a coil or cdi going crazy and causing issues like this or do they typically just stop working in all? Thanks again, Thomas Quote Link to comment Share on other sites More sharing options...
J-Madd Posted March 28, 2011 Report Share Posted March 28, 2011 Based on the information you gave, the motor is definitely detonating because that is the only thing that will shatter a plug. If it is something that has just developed over the years, then more then likely the problem is an air leak. If you blipped the throttle, would the rpms comes right down or do they come down slow? The first test I would do it to see if there is an air leak. This is very east to do with just a few parts. First you will have to remove the pipes and carbs. If you have a stock bumper, take the rubber ends off and bumper, get a hose clamp that will fit over it and then put those ends on the exhaust flanges making sure to tighten down the hose clamps. Now go to your local hardware store and by a set of electrical pipe ends that are close to 28mm or 1 1/8" inch. You can also use a PVC end that also has an OD of 28mm or 1 1/8". Now buy a schrader tire valve(the kind that have nuts on both ends and then drill a hole in one of the caps you bought to stick in the intakes. No matter what size you choose. Now make a hole to you can screw the. Now normal case pressure is between 4-7 pounds, this is not really important but it is good to use it as a guideline so you don't pump in to much air when you check to see if the motor is sealed. Now that you have the intake and exhaust sealed, pump up the cases with about 6lbs of air. Now wait for at least 15 minutes and then check the pressure again. If it is still at 6lbs, then you have no leak. If it loses any air within the 15 minutes, then you have an air leak and will need to find it. The best way to find the leak is to remove anything that covers seals(side covers, flywheel and the area where the to case half's meet) then pump it back up to about 6lbs and spray with soapy water and you will find leak by looking for spots that soap bubbles are forming. Now that you have found the leak, you will need to fix it and that depends on what is leaking. If there is no leak, then my second guess would be that the gas you are using is bad, probably from sitting over time. It may also have low octane and the motor requires that higher octane fuel be used. If octane is the problem then the fix is the easiest to fix. Just by better gas like some race fuel. If your motor is not set up with that much compression, you can also get away with a 50/50 mix of regular. If you do these two tests and nothing changes, then there must be a more serious problem. Good info, except that he's running alcohol. Did you try swapping carbs side to side. If problem moves, it's in the carbs...otherwise sounds like a clutch side air leak. Is your basket sealed at the shaft? Surely you mean the primary gear keyway, not the clutch basket??? Usually a bad seal on that side will draw in tranny fluid and leave deposits on the plug. It will burn the fluid but not usually burn down a cylinder. While swapping carbs left to right will rule out certain issues, I'd hate to ruin the other cylinder just to rule out an air leak on one side. Try a different set altogether if you want to rule out a carb issue. There has to be an air leak somewhere, or a bowl is running dry, or something. Maybe its the base gasket?? I had a bad base gasket keep burning plugs. It didn't run erratic like you think it would. Are you running a new gasket every time you put it together? I ALWAYS pressure test any motor after it has been apart, regardless of the condition it was in before. What kinda shape are the bearings in on the bad side? 3 melt downs can't be good on the crank. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted March 28, 2011 Report Share Posted March 28, 2011 What are the specs on the carbs? Are they sync'd? Maybe one carb isn't opening up all the way, which would lean that cylinder out. YOu have powerjets, right? If so, make sure one isn't vibrating closed. I have seen that also. Quote Link to comment Share on other sites More sharing options...
trex banshee Posted March 29, 2011 Author Report Share Posted March 29, 2011 What are the specs on the carbs? Are they sync'd? Maybe one carb isn't opening up all the way, which would lean that cylinder out. YOu have powerjets, right? If so, make sure one isn't vibrating closed. I have seen that also. the carbs are syched yes..and on the powerjets they are actually just another main jet. Andy at GRR converted them years ago and just drilled and tapped the carb for the jet. They have worked flawlessly for about 5 years on other bikes then this issue, but that does not rule it out. I was just leaning more towards an ignition problem due to the fact that it doesnt really burn down or melt down, everything still looks great as far as color goes, the only reason why i need a new piston everytime is because when it smashes the porcelin of the plug that dings it up and the dome, the rings are still very free and can be taken right off. Also yes, i have replaced the base gaskets everytime and this last time i even used some adhesive for extra insurance. Im just wondering if it is still a lean issue due to an air leak but it is only at WOT and only takes just a split second the shatter the plug that it never changes the plug white or make the piston look like it is burnt. There are many issues that need to be addressed and getting the stuff to do a leak down is my first step for sure. Im not about the just swap the carbs to check that, lol. I do however have a completely other set i could try but i dont believe i have the intakes for stock cylinders and 39 carbs. Thanks for all the help again guys. jmadd, did you hear about travis? Quote Link to comment Share on other sites More sharing options...
J-Madd Posted March 29, 2011 Report Share Posted March 29, 2011 Any chance the head is letting water in that cylinder? Quote Link to comment Share on other sites More sharing options...
Nightrider Posted March 29, 2011 Report Share Posted March 29, 2011 Sounds like detonation to me, only thing that would shatter the plugs like that. looks like your getting just enough to wreck the plug. Maybe a combination of lean condition and bad alky? Quote Link to comment Share on other sites More sharing options...
Mike Z Posted March 29, 2011 Report Share Posted March 29, 2011 Good info, except that he's running alcohol.[/color] Alcohol doesn't detonate huh? You better educate yourself more if you think alcohol doesn't detonate. Why don't you put some 14cc domes on your bike that runs alcohol, and tell us what happens! Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted March 30, 2011 Report Share Posted March 30, 2011 (edited) Good info, except that he's running alcohol.[/color] Alcohol doesn't detonate huh? You better educate yourself more if you think alcohol doesn't detonate. Why don't you put some 14cc domes on your bike that runs alcohol, and tell us what happens! I believe this is why J-Madd posted that info. I don't think he was making a personal jab at you ethire. He was just stating that the O.P. was running methanol and not gasoline. I am sure J-Madd is verry aware that methanol can detonate as he runs several banshees on it. If the O.P. was supose to take your advice on the fuel, what fuel would you reomend running through a set of keihin carbs that have been moddified for methanol and has a higher octane rating than methanol? It may also have low octane and the motor requires that higher octane fuel be used. If octane is the problem then the fix is the easiest to fix. Just by better gas like some race fuel. If your motor is not set up with that much compression, you can also get away with a 50/50 mix of regular. Edited March 30, 2011 by jbooker82 Quote Link to comment Share on other sites More sharing options...
trex banshee Posted March 30, 2011 Author Report Share Posted March 30, 2011 im not 100% sure what is happening first, once it dropped the cylinder this last time it puked all the coolant out. Could it have been slowly burning coolant this whole time which was causing a hydraulic lock in the cylinder shattering the plug? Then the third time finally blowing the oring completely? Honesly i really dont think that i put new orings in the head. That would explain the fact that the overall color of the cylinder wall and piston top and skirts and plug looks great. Im open to anything, and mike z j-madd didnt mean anything at all towards you, he is a very nice guy and would do anything to help you. I believe he said what he did because you kept saying 'gas' in your post and that you would recommend to run a 50/50 mixture. Quote Link to comment Share on other sites More sharing options...
Mike Z Posted March 30, 2011 Report Share Posted March 30, 2011 im not 100% sure what is happening first, once it dropped the cylinder this last time it puked all the coolant out. Could it have been slowly burning coolant this whole time which was causing a hydraulic lock in the cylinder shattering the plug? Then the third time finally blowing the oring completely? Honesly i really dont think that i put new orings in the head. That would explain the fact that the overall color of the cylinder wall and piston top and skirts and plug looks great. Im open to anything, and mike z j-madd didnt mean anything at all towards you, he is a very nice guy and would do anything to help you. I believe he said what he did because you kept saying 'gas' in your post and that you would recommend to run a 50/50 mixture. See, most people take my replies wrong. I wasn't trying to condescend j-madd, I was just merely saying that it does. I guess the huh at the end might have made it sound bad, but I was just saying that it does. And I can tell you with 100% certainty is that the only thing that will break a plug while it is in the motor, is detonation. One of the reasons spark plug are made out of porcelain is for that very reason. You can through it at the ground to try to break it and I bet you will quit before it breaks. But don't listen to me, I'm just a know it all A$$hole that knows nothing even though I have blown up and built more motors then most members age on this site. Quote Link to comment Share on other sites More sharing options...
trex banshee Posted March 30, 2011 Author Report Share Posted March 30, 2011 See, most people take my replies wrong. I wasn't trying to condescend j-madd, I was just merely saying that it does. I guess the huh at the end might have made it sound bad, but I was just saying that it does. And I can tell you with 100% certainty is that the only thing that will break a plug while it is in the motor, is detonation. One of the reasons spark plug are made out of porcelain is for that very reason. You can through it at the ground to try to break it and I bet you will quit before it breaks. But don't listen to me, I'm just a know it all A$$hole that knows nothing even though I have blown up and built more motors then most members age on this site. hey man you need to chill. none of us are meaning to come across the way you think. and i believe i dont recall any of us calling you just a know it all asshole. Im not saying i dont believe you, not at all. i would just rather get as many opinions as possible, im not ruling out your theorys at all. I will have to disagree with you on the spark plugs breaking though. i work at a parts store and things get dropped, it happens...and they will break. Quote Link to comment Share on other sites More sharing options...
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