400EX spark knock problem

[Blown 331]

My cousin bought a 1999 440EX and the owner said it was fine on 93 octane. My cousin put 93 in it and is spark knocked so he started running 110 but it was too late and blew the head gasket and cracked the piston (JE). .

He got it back together with a 11.2 to 1 Powroll kit. At this time he ported the head him self and put on a flat slide carb from a CRF450. It didn't run like it should, he tried swapping carbs back and that didn't really help. He was running 110 in that but put 93 in it when he ran out of gas and blew that head gasket too! He put a stock head on it thinking his port job messed it up but that didn't help and he blew another gasket. Well the bike is sitting apart and we're not sure what to do with it. He wants to run pump gas but it has the worst spark I've ever heard. I'm talking in first gear you give it half throttle and all you hear is spark knock, it's crazy!
He bought another 440 cylinder off ebay for next time around. He also has the biggest cam web cam makes and his valves have been making slight contact with the pistons, both set ups. He thinks that cam is preventing it from making power like it should, too big. But that cam is still no where near the size of the HRC cam in my 450R, so I'm not so sure that's it.

I think it should run on 93 octane with 11.2 to 1 compression. He has tried 2 heads to I don't think he has a milled one. We also check to see if it had an advanced flywheel key, nope. Any ideas why this thing spark knocks so bad? He is thinking about running 2 head gaskets and like 6 base gaskets. lol. Looking for some imput here.

well, the valves hitting the pistons is definatly not good lol..

Mine has this annoying TICK and it kinda drives me nuts.. is that what your hearing? i have a 11.1 JE and i run 93 with absolutly no issues at all, but a 11.2:1 may be a bit different, as you may know.

One thing to check is the head studs, are the the heavy duty jobbers? I have heard and read many people saying the stock head studs will pull out and cause the head gasket to blow everytime.. Even tho it may look like they are in there sturdy, with a 440 your swinging one hellava piston..

Is there alot of play in the wristpin/rod area?

One thing with webcam's as good as they are, some of there lift/durations are too much for the bikes to handle, not saying they dont work well, just some of them are too much.. I would much rather deal with a .010 clearence than a .001 @ 10k rpm yanno?

Shoot me a message on aim @ linux krnl and ill send you a video of some different taps, knocks, and what not and can narrow it down a little more for you

Jesse

btw, find a r motor yet?

[Blown 331]

He got head studs put in it. I'm not totally sure on this but I think he sent it to Ohio and FTZ put in studs. Does that sound right? There no play at either end of the rod. What piston do you have to only get 11 to 1 compression? Does anyone offer a 10.5 to 1- 440 piston? It only makes slight contact with the piston, never bent valves but you can see marks.
It's definitely spark knock we are hearing. It doesn't do it when running 110 octain leaded fuel. I still don't think that should be needed though. He wants to run pump gas.

Yep got a motor for my 3-wheeler. Nothing special, has some work done to it but a stock cylinder. Runs good in that light bike. Just needs a bit more and it will beat my 450R. Hangs pretty good the way it is.