Aitchy Posted September 1, 2009 Report Share Posted September 1, 2009 (edited) I feel for ya, Im in the same boat, What is it with that left side ?????? I nipped mine up , a week later my mate nipped his up same side Both right sides are fine ,Cryin shame " FOR SALE 1 X 65.00 .040 O/S & 1 X 65.25 .050 O/S Wiseco , Cheap good as new lol " Cheers, Aitchy. Edited September 1, 2009 by Aitchy Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 1, 2009 Author Report Share Posted September 1, 2009 Did you break the motor in on 40:1 as well? Yes I did Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 1, 2009 Author Report Share Posted September 1, 2009 What are you doing for assembly lube? I wipe down the cylinders with the premix oil, aswell as the piston skirt and lots around the rings and ring lands. Also, I put a bunch of drops down into the crank bearing lubrication holes. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted September 1, 2009 Report Share Posted September 1, 2009 Well...it does sound like you covered your bases....and your specs seem to be damn near spot on. Are you using a stock fuel valve or a pingel? If the carbs are new...and clean, I don't see that being the issue. If your piston to wall clearance and ring end gap are fine, I think you're running out of fuel. A faulty ignition can cause it to run like crap, but won't melt it down like that. Did you see any signs of Orings in the head breaking/leaking. Here's my thoughts...either it's running out of fuel OR the surface of the cylinders or the head/shell/domes isn't sealing right. If you suck antifreeze it can lean out in a hurry. Quote Link to comment Share on other sites More sharing options...
mopar1rules Posted September 1, 2009 Report Share Posted September 1, 2009 Im using Yamaha 2-R oil since this rebuild and mixing at 40:1. Correct me if I'm wrong but I thought that was a safe ratio to mix at. Also, what kind of plugs do you guys use? Im using NGK BR9ES plugs. Could a leaking exhaust O-ring at the jug cause air to be sucked in when the exhaust pulse creates a vacuum in that area and then the pulse from the forcing cone coming back towards the port push the air into the engine? br9es plugs (common sled plugs), are 1 range cooler than stock. b8es is the stock plug. those br9es plugs didn't cause that melt down. Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 1, 2009 Author Report Share Posted September 1, 2009 Well...it does sound like you covered your bases....and your specs seem to be damn near spot on. Are you using a stock fuel valve or a pingel? If the carbs are new...and clean, I don't see that being the issue. If your piston to wall clearance and ring end gap are fine, I think you're running out of fuel. A faulty ignition can cause it to run like crap, but won't melt it down like that. Did you see any signs of Orings in the head breaking/leaking. Here's my thoughts...either it's running out of fuel OR the surface of the cylinders or the head/shell/domes isn't sealing right. If you suck antifreeze it can lean out in a hurry. Im using a stock fuel valve. I used a chariot cool head for this build and it is brand new, never used. When I disassembled the engine, all the o-rings looked fine and I didn't see any signs of coolant being burnt. The domes were spotless still, and the plugs didnt have any deposits, they were a dark brown colour ever since break in. I didn't check the piston to cylinder clearance because I assume that was done when the cylinder was bored and honed but I realize I should have. I believe the ring end gap was around 0.012" but I could be wrong, I have it written down. I'm at work right now so Ill look when I get home. I still cannot believe this happened, I was so careful and took my time putting the engine together because I have a lot of money into it this time. Both times it melted the right pistons it was pretty well a stock engine and now I have replaced almost everything. Quote Link to comment Share on other sites More sharing options...
ToomeySheeLE Posted September 1, 2009 Report Share Posted September 1, 2009 It wouldn't hurt to run a tank of 24:1 - 32:1 through it first before switching to 40:1.. Its good to break them in with a richer oil mixture in my opinion.. but even so, I dont think thats what caused this.. It does look like a lack of fuel and or air leak, but it sounds like you went through all the right steps.. Fuck there's nothing worse than not knowing for sure what the hell caused the failure.. Hope it can be figured out. Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 1, 2009 Author Report Share Posted September 1, 2009 (edited) I noticed this morning when I was cleanig the pipes off that there is burnt oil residue that has run down from a weld in the left pipe about half way between the jug flange and the expansion chamber. So there has to be a pinhole in the weld that is leaking exhaust, could this suck in air too? The hole is on the same side that melted the piston, I suppose It could just be a coincedence. One more thing, does anyone know the average running coolant temperature for a build like mine? I have a trail tech vapour mounted and riding through the trails it stayed around 140 - 150 degrees F but when I was riding in the sand pit it got up to about 185 degrees. I usually wait till it is up to 110 - 120 degrees before I even start riding. Edited September 1, 2009 by 03bansheeLE Quote Link to comment Share on other sites More sharing options...
J-Madd Posted September 1, 2009 Report Share Posted September 1, 2009 Not gonna help you now, but if you would've done a pressure test AFTER the damage, before disassembly it would at least rule that out. However, the many times that I've burned a piston, I'm always anxious to get it tore down, and always forget to perform a pressure test most of the time. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted September 1, 2009 Report Share Posted September 1, 2009 I doubt the pinhole did it. I had several on my pipes from the last time at the track, and it actually cracked on the seam and I still made a bunch of passes. Stupid, I know...but didn't hurt the motor at all. Bigger bowls or a pingle would be my next bet. While the air/fuel mixture is probably fine, if it runs out of fuel...it won't survive long. Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 2, 2009 Author Report Share Posted September 2, 2009 Not gonna help you now, but if you would've done a pressure test AFTER the damage, before disassembly it would at least rule that out. However, the many times that I've burned a piston, I'm always anxious to get it tore down, and always forget to perform a pressure test most of the time. Yea I totally thought of that after I tore it apart, it would have definately ruled out a vacuum leak but I will check it when I put it together again. Going to go up a couple sizes on the jets and be real careful this time. Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 2, 2009 Author Report Share Posted September 2, 2009 I doubt the pinhole did it. I had several on my pipes from the last time at the track, and it actually cracked on the seam and I still made a bunch of passes. Stupid, I know...but didn't hurt the motor at all. Bigger bowls or a pingle would be my next bet. While the air/fuel mixture is probably fine, if it runs out of fuel...it won't survive long. Alright it was just a thought, how about leaking exhaust o rings at the jug? Im just getting ready to order pistons and gaskets so Im getting a pingle valve too. I think Im going to get nology coil and wires aswell, they are original so it can't hurt to change them. Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 2, 2009 Author Report Share Posted September 2, 2009 It wouldn't hurt to run a tank of 24:1 - 32:1 through it first before switching to 40:1.. Its good to break them in with a richer oil mixture in my opinion.. but even so, I dont think thats what caused this.. It does look like a lack of fuel and or air leak, but it sounds like you went through all the right steps.. Fuck there's nothing worse than not knowing for sure what the hell caused the failure.. Hope it can be figured out. If I were to use 32:1 instead of 40:1 I would have to use larger mains right? More oil = less gas per volume of air/fuel mixture that goes into the engine. Therefore it would essentially be running a leaner air/fuel mixture but with more oil. Correct me if Im wrong but I might try this. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted September 2, 2009 Report Share Posted September 2, 2009 If you're running pump gas, 32:1, race gas (leaded) 40:1. From the sounds of things, I don't think it was a jetting problem...I think it was running out of fuel...to be honest. Quote Link to comment Share on other sites More sharing options...
03bansheeLE Posted September 2, 2009 Author Report Share Posted September 2, 2009 If you're running pump gas, 32:1, race gas (leaded) 40:1. From the sounds of things, I don't think it was a jetting problem...I think it was running out of fuel...to be honest. Im using 94 octane pump gas so ill try 32:1. Have you heard of the cdi screwing up or something with the flywheel triggers causing the timing to advance too much? Quote Link to comment Share on other sites More sharing options...
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