I tried sticking a flat head under the spring and lightly prying on it but it is pretty right and the spring stretched a tad so I don't think that's the case. The spring did not lift out.

Another tid bit of information for help with diagnosis; Prior to this all happening, I noticed a sound that I thought sounded like a ping. I brought it up on the forums, but I was advised that it was probably something minor like the gas tank rattling or something. (I originally thought that it was rocks getting thrown off my new tires into the engine or my keys rattling against the triple clamp) Someone suggested I add a little bit of octane booster to see if the pinging goes away. I did this, and that is currently the tank of gas I am on.

 

Question for those of you with the 351 kit:
Does the new piston have valve reliefs in it and are the intake and exhaust reliefs the same? Just thinking that maybe the piston went in backwards and there was less clearance between the valves and the piston. Some high rpm valve float and BANG!

Ride on
Brewster

 

For this reason Bill draws an arrow on the piston with a sharpie as to the way it is to be oriented facing forward. It should only go in this way....

 

I don't think the top of the valve would be sticking up like that, if it wasn't broken - unless the keeper let go, in which case you should be able to pull the spring out. I'm thinking the valve is broken, and the part you see can't be pulled out because the broken end is a bit bent or mangled & won't let it come through. Why it broke is another thing, sure sounds like piston/valve contact, and maybe Brewster has nailed it. Kind of why I was wondering how much room the valves would have after the cam mod changed the timing - maybe adequate for stock setup, but not enough for big bore with some valve float, and really not enough if the piston is in backwards from what the reliefs look like.

I gotta say, this was a great board before jhoffy started posting, now it's on a whole other level if interestingness. Really hope your luck turns dude - I can't say anything about other peoples bad luck after the booboos I've made. Good luck.

 

just take the cylinder off and have a look
Do you still have your stock cylinder and piston?

 

Looks like the 351 piston has more relief for the intake side. If the piston was indeed installed backwards wouldn't it be an intake valve that would suffer the failure ?

 

I need to figure out what needs to be replaced now.

 

It might be helpful if you could find out why it happened also.

Did you check your cam timing before you tore it down? Any chance it jumped somehow? Everything look OK in the cam sprocket/chain/tensioner department? Otherwise, it appears maybe a bit of float combined with too close tolerance - it would seem to be too big of a coincidence to have a valve suddenly break like that out of nowhere unless previously weakened. Also looks like the piston was in right, and also like was said above, if it was wrong I think the bigger relief would go to the exhaust side anway.

Tough one...

 

No idea why it happened yet. I'm sick to my stomach about it though. I need to figure out everything that I need to replace to fix it and why it happened so it doesn't happen again. The timing was spot on, nothing jumped or anything. Yes, everything looks good with the cam sprocket/chain/tensioner. I'm not sure that I suggest anyone do the camshaft mod that has the 351 kit. Bad idea. It has to be what caused it. The bike was running fine and then all of a sudden - bam!

 

That's harsh! Sorry about your KLX troubles jhoffy. One thing positive is you should try to learn as much as you can about why this happened so you'll be older and wiser when it's all behind you. Someday you'll sit back with a beer in hand laughing about the KLX you blew up. Meanwhile, school is in session, don't forget to take notes.

Good luck with your rebuild bro!