Wellsy Posted June 3, 2006 Report Share Posted June 3, 2006 We have had our first real day of sun here in the UK today so it should have been an excellent day quading but again after only six or so outings since my last seized piston it has happend again. (to top it of my Mrs TRX250R seized as well) Only the right piston (as you sit on the quad) has seized with no signs of problems with the left piston. This is the second time this has happened!!! I am running PJ34's which are cleaned after every couple of outings so I am trying my best to keep on top of the maintenance. The piston are vito's super stock, I have a K&N filter and FMF full exhaust system. Oh and the quad is an '05 model. I am mystified why this is happening to the same side time after time. Its becoming annoying to say the least and very expensive to rebuild the top end. I have two rebores left so I can not afford another seizure. Please can some kind soul offer some advice on what is causing these seizures before I have to re-mortgage the house. Quote Link to comment Share on other sites More sharing options...
watkins Posted June 3, 2006 Report Share Posted June 3, 2006 Have you performed a leakdown test yet? If it keeps happening on the same side I would think you have an airleak. Are the carb boots cracks? Base gasket leaking? Crank Seals? Its too late to test now, but when you get it back together spray it down with Starter fluid and see if it starts reving up as you spray. Quote Link to comment Share on other sites More sharing options...
lowriderb Posted June 3, 2006 Report Share Posted June 3, 2006 on top of a leak down, were you letting the bike get fully warmed before taking off on it? also are you sure that the bore wasnt too tight for the pistons? as well as getting fuel to that side carb? (running stock petcock) what were you doing when it seized? Quote Link to comment Share on other sites More sharing options...
Toybreaker Posted June 4, 2006 Report Share Posted June 4, 2006 (edited) I had been on the quad for about ten minutes with medium throttle and then me and mate (on hit TRX440) decided to have a race. At the time of seizure I was on full throttle giving it all I can in third gear. Then the motor died and locked up. Whats the requirement of an upgraded petcock as I think the one on the shee is standard. Could the reeds have closed or be damaged? Thanks for your replies so far. Show us the fragged piston. It could be you are running lean on that side due to an air leak. I also learned the hard way that if you melt a piston tear it all the way down and thoroughly clean out the crank bearings and replace the crank seals while you are there. Edited June 4, 2006 by Toybreaker Quote Link to comment Share on other sites More sharing options...
lowriderb Posted June 4, 2006 Report Share Posted June 4, 2006 see about doing a leak down test searching for an air leak, it does sound like you leaned out did you change anything thing with the tuning since the weather has changed? and here is what people use for an aftermarket petcock http://www.pingelonline.com/hex_dual_race.htm they are about 80 bucks shipped from them, and very worth it so you dont have to worry about not getting any fuel.. Quote Link to comment Share on other sites More sharing options...
Wellsy Posted June 5, 2006 Author Report Share Posted June 5, 2006 (edited) Not a nice sight as you'll all agree! Here is a picture of the melted piston along side the unmelted piston. Why only the one side again!!? I will order the upgrade petcock that lowriderb has suggested to eliminate another potential problem. With only one rebore left is it worth getting another set of cylinders either used of ebay or, a re-sleeve or go mental on a 421cc big bore set up from vito's? Remembering I will be using this to compete in MX. Edited June 5, 2006 by Wellsy Quote Link to comment Share on other sites More sharing options...
canyncarvr Posted June 5, 2006 Report Share Posted June 5, 2006 (edited) Make sure the crossover tube (cold enrichment) is in good shape AND properly fit. One that is not will destroy the RH piston. **edit** That comment intended for VM26ers, no application to Keihin. I glossed over the PJ part. If the petcock is restricting fuel flow the first piston most likely to feel it is the left piston, not the right. Edited June 5, 2006 by canyncarvr Quote Link to comment Share on other sites More sharing options...
lowriderb Posted June 5, 2006 Report Share Posted June 5, 2006 where the flow goes depends on how the fuel lines are ran, with the stock petcock the tee can be pointed more towards on carb more than the other (more vertical) and the liquid will flow where there's least resistance.. which can lean towards either carb. a crank seal that would cause an air leak would be the left side, the right side would be burning oil.. blown head gasket (stock head) is possible (if no air leaks were found anywhere else, check the base/intake gaskets as well) if the bike were to run out of coolant (which would be blowing out of the over flow) it would lean out because there wouldnt be anything there to seal against. blown o-ring (aftermarket head) would be about the same as a blown head gasket.. the big bore sleeves will cut down big time on the transfer area in the stock cylinders.. also for the cost of it you could get a cub setup (or similar cylinder setup) Quote Link to comment Share on other sites More sharing options...
Wellsy Posted June 5, 2006 Author Report Share Posted June 5, 2006 (edited) Thanks for your replies lowriderb and all The petcock theory makes perfect sence so I will order a upgraded petcock from you suggested supplier. Lowriderb when you talk of bad crank seals ie left gives an air problem and right gives an oil problem are your refering to the cylinder as if you are sat on the shee or from the front of the quad. On Saturday when the piston seized I had noticed a slight leak that was running down the frame and dripping on to the rear of the lower right (as you sit on the quad) a-arm. I assumed it was from the radiator overflow pipe as it was a hot day (80+ degrees F). I lost less than a 1/8 of an inch of coolant all day. Canyncarvr mention the crossover tube on VM26ers (Mukuni's I think) and that made me think of the possibility of the Boost bottle seals being to blame. Any thoughts? Now that the cylinders are off I will replace Head gasket, Base gasket and intake (reed cage) gaskets as well as checking the carb boots. The Cub cylinders sound appealing but I will have to raid the piggy bank and sell all my worldly posessions on eb*y. Thanks for your info so far. Please keep telling me of other possibilties and details of other items that I should check. Edited June 5, 2006 by Wellsy Quote Link to comment Share on other sites More sharing options...
lowriderb Posted June 6, 2006 Report Share Posted June 6, 2006 im meaning from when your sitting on the bike (left is stator side and right is clutch side) the stator side would be open to air, the clutch side would be open to the crank case oils.. the reason why i would suggest getting the cub cylinders over putting in the big bore sleeves in the stock cylinders is because it would cost about the same total (sleeves installed and port matched) Quote Link to comment Share on other sites More sharing options...
canyncarvr Posted June 6, 2006 Report Share Posted June 6, 2006 re: '..possibility of the Boost bottle seals being to blame.' Anything leaking (including the balance tube and/or bottle hardware) can lead to a seizure. Yes, the type, angle, of the petcock, and routing of hoses matters. Generally speaking, the petcock being on the LH side, the LH carb hose route is shorter than the RH carb hose route. That gives you more fuel 'storage' in the RH setup. You can turn the fuel off and see which cylinder runs out first. (Not a recommendation btw..) Obviously a completely different carb setup would be..well..completely different. It is not uncommon to have different jetting requirements for the two cylinders even with everything else (boots/reeds/bottles etc) OK. Good luck! Quote Link to comment Share on other sites More sharing options...
lowriderb Posted June 6, 2006 Report Share Posted June 6, 2006 im sorry but they are "twin" cylidners not "similar" cylinders.. ive never jetted one side different than the other... if they are needing different state's of tune for each side then there has to be a problem seeing how they are supposed to be exactly the same.. could the stock carb on the right side have something clogging the fuel inlet, or main jet.. outside of that i would search for an air leak somewhere down the line.. Quote Link to comment Share on other sites More sharing options...
96dragbanshee Posted June 6, 2006 Report Share Posted June 6, 2006 I would agree with most people that is probably an airleak, but if u do a leakdown test and find out it isnt. Check and make sure ur spark plugs are the same brand and same number. Next check and make sure your carbs are sychronized. But my guess is airleak when was the last time you had the bottom end rebuilt or changed the crank seal. That could cause it. If you do all this message me if u dont figure it out. I may be able to help u more when i can get pictures of the piston. Quote Link to comment Share on other sites More sharing options...
Wellsy Posted June 7, 2006 Author Report Share Posted June 7, 2006 Ive have pictures of the pistons but cannot attach or insert them. Perhaps this because they are high res macro pictures. Any idea? Quote Link to comment Share on other sites More sharing options...
lowriderb Posted June 8, 2006 Report Share Posted June 8, 2006 email them to me and ill post them for you.. lowriderb2001@yahoo.com Quote Link to comment Share on other sites More sharing options...
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