Thanks for the information you put together for CCing for compression ratios.

Save your money. On my particular quad on the first failure. It was rode for quite a while with oil coming out of the crank case vent tube. At no time, ever, did smoke come out of the pipe. At startup, idle, high rpm runs or anytime in between. There is almost always someone behind me and in front of me when I'm riding.

The second failure happened so fast there was not enough time running it to see any smoke coming from the pipe. The piston itself lasted longer than the first but, the failure occured all at once instead of gradual.

 

i have had an 11to1 piston do the same thing. it starts cracking around the wrist pin bosses and then a piece falls out from the cracks connecting to form a triangle.
i recently took my 105mm piston out and it also had cracks around the wrist pin bosses.
there is definitely an issue with the design or materials used, regardless of how hard these engines are run.

 

Thats not good news. First JE piston other than the 11:1's that I have heard about that have had similar problems.

 

wow, some cheap pistons huh, thats terrible

 

Well, after taking a day to read through this thread I hope that my year old, just installed 11:1 JE piston holds up along with the stage 1 hotcam. I broke em both in just today. Im running Chevron pump 93 octane.. no probs so far. Redskin your jetting recommendations were pretty close. I am using 27.5 pilots, 2 turns and 180 and 185 mains. I'm losing a little on the top, I'll try 185-190 next. First I putted around for about a half hour let her cool off then fired her back up and let her rip....By the way, it seems harder to turn over now???? From what I remember it's a little quicker on the bottom but the midrange is great.....man I defenitely need to go back up to a 13 tooth up front, I'm revving out the gears way too quickly. I also notice that the "ticking" from the cam is a lot louder...almost annoying. Anyhow...I'll keep ya'll updated on how she's holdin' up...Thanks

 

Delta,

Tighten up the clearance on the valves. I use 6 thousanths on the intake and 8 thousanths on the exhaust. Hot cam recommends 8 and 10 respectivly. This will quiet them down some. Just keep an eye on the clearance and you'll be fine.

 

Yeah, I have had my valves adjusted 2 times since I got her back together and the valves on the right side of the bike seem to be ticking pretty loud. I have them set to Hot Cam's spec's, but they seem lose. I just figured I would follow the spec's hot cam gave me and run it like that.

 

Hey Doctor, have you ever seen a Vacum opperated fuel pump?? It's tapped into the intake between carb and cylinder. It pumps fuel by using the negative/positive pressure in the intake.
What happens if you have a leak between the carb and cylinder?? The engine will draw air through this leak creating a leaner mixture because the engine needs more flow then the carb can provide (this must be the case for a carburator to function)
With a 102mm bore (8167.14mm sq) and two 33mm carbs (1709.73mm sq) intake velocity would be approximately 4.7768 times the piston velocity at WOT. What happens when you accelerate air through a ventury?? The PRESSURE DROPS!!! (The same way an airplane flys. The airfoil shape of the wing accelerates the air over the top creating a lower pressure. Now the pressure is lower above the wing then below, thus creating lift.
You do need very fast responding and sensitive gages to measure it. Your regular 0-15 In/HG gage won't do the trick, LOL
Air flow will come from the path of least resistance but the path of least resistance is restricted so it will draw air from where ever it can!!!!
If an engine with a cracked piston didn't smoke it was because the crack was to small.
Sixsix, you hit the nail on the head. There is no sign of a lean mixture or detonation, so I would have to lean toward a piston design or manufacturing flaw as well.
Ray

 

The only other thing I thought of since my last post was harmonics. Changing piston weight. But it's usually OK to go to a lighter piston. With rods, wrist pins and pistons cracking/breaking it's possible that harmonics could be a problem. I don't know how it could be tested but I do know it can do all kinds of damage to all parts of an engine including snapping cranks.

 

Is anyone having their engines balanced? I know that it's only one cylinder and chances are it would be ok but is anyone having the extra step done... especially in the case of a new Carillo or other aftermarket rod.