you need to pull the piston and cylinder too. The edge of the piston could have collapsed on the ring causing it to bind up. This would require a new piston. Also run the piston down in the cylinder and see if the walls are scored. Any groove will make it so the bike will not run even with a new head.


as far as why it happened, it could have been a clearance issue like timing or something could have gone through the engine causing the valve to bend then stick open then break

I can only speculate.

David

 

Sloooow dooowwn man, take some air

 

I'd really like to see someone to do some putty or solder (or whatever) valve/piston clearance checking when they're doing the cam mod, and report on it - both stock & big bore. Would be kind of a pain to go thru the head/valve train assembly twice, but seems more info on that might be quite helpful - especially with the way this one went.

 

I'll take pictures of everything and post them on here. It's going to be over $1,000 to fix everything in just parts and I'm not even sure that Bill can sell me just the piston and the rings. I'll probably also want to pay a mechanic to do it so it's not as likely to happen again. I don't know if it's even worth it. Terrible situation.

 

I ran the piston down by cranking the engine by hand. The sleeve doesn't look scored. The timing was good, I checked it multiple times after torqueing everything down and then before I took the engine apart tonight. I have no idea what could have caused this. The piston is shot though. I don't think I can use this again, can I?

 

No, can't use the piston...at least in the engine. As a paperweight or ashtray, it would be fine.

I would assume that Bill would sell you just the piston/gasket kit to replace those parts.

 

Am I seeing a couple of symmetric dimples from the other exhaust valve on the piston?...or just chance divots from the loose valve head? I'm not sure that the cam timing mod can be absolutely identified as the cause here, can we? The rather helter-skelter assembly process might have had something to do with it. Not dissin' you jhoff, just looking at all possibilities here. Still, this cam timing mod does retard...slow down...when the exhaust cam shuts the valve, doesn't it? Maybe some here will be glad you went at this mod with the 351 in such a rapid manner after all.

 

Yeah, it's the exhaust valve that was stuck open and lodged in the piston. So I'm nearly 99% positive that this is something that you don't want to do with the 351 kit. I deserve the dissing, but I guess it's better me than someone else. I hope nobody else has any experience like this. I'm really wondering if I should try to rebuild this. I'm going to be looking at >$1k in parts alone. And then trying to find a quality mechanic. The bike is an 06 and had 5k miles when I bought it 2 months ago. I got it for $2,100.

 

If anyone wants to give me a call and walk me through some standard "engine melt down procedures" to try to figure out the cause of this, that would be great. I just don't want to invest any more money in this bike until I figure out the exact cause of the problem.

 

From bad to worse. Good luck man..

And I doubt it was the cam mod that did it. If it was running fine for a while, then grenaded, it was something else. If the cam mod allowed piston to valve contact, it would have grenaded the first time you fired it up - if it even fired. It would probably just throw the valve before that happened.

Something let loose at a high RPM.

Where are you located?