2001 raptor, ported stage 2 cam w/686 kit, was running fine now, it has a terrible knock in it, tore down the top half and found the valve was hitting the piston, but all the parts look alright, any ideas, can i shave the one piston pocket down 30 thousand to cure the problem??

 

Check for tight guides ,bent valve and have the springs tested .

 

thanks, yes the guides and the valve are alright, not even alot of carbon build up on them, can check the springs if I find the measurements from the dealer I bought them from, they are supposed to be a different spring from stock, called Trinity Racing after posting this message and they said I could cut the piston 30 thousand, just have to be real carefull, guess the biggest problem now is finding a quality shop for the machine work.....

 

Is the middle valve 1mm or 2mm over? Who sold you the valves? Are the valve springs double, or single per valve?

I have seen a Trinity build with a 2mm over center intake valve and it was hitting the piston also, but the biggest problem was the valve was not even a Heat treated Ferrera Valve. It mushroomed real bad on top of the valve where you adjust the valves.

Your best bet is to call Bob Craycraft at 817-441-5893

 

hey, the mechanic that tore my machine down told me the valves are stock yamaha, springs are single, all parts looked alright, that's what was throwing us off as to why it started making the noise, I am beginning to believe that I did not get what i paid for, had a part-time mechanicc do the work and he sent the head off to be ported, not sure where, thought the guy would do me a better job than this, life and learn, yes, i will call craycraft, if they can not fix the problem here, i will load the quad and take it craycraft and have him go over the entire engine, thanks......

by the way, have you ever been to the Kermit dunes? if I ever get my ride fixed, lets hit it sometime....

 

Sounds like your builder did not set the engine timing correct.

 

Not necessarily.......we also have a 2001 Raptor with the same bore and Stage 2 Hotcam that also has the same problem with the valves hitting the piston - broke a rocker arm due to this and have to get all new top-end. Timing and everything was set right.......valves were adjusted properly........hmmmmmmmm

 

Could be a wore out timing chain letting the cam rotate a tooth off. My first suspician would be timing incorrectly set.

 

I bent the middle intake valve, reason still unknown. New valve, seat, guide, etc and it has worked fine since.

Some people have stated that you have to shorten the valve guide for the middle intake valve when you use a stage 2 hotcam, perhaps there is something to this. But my replacement was stock length with an 11:1 stock bore.

 

The deal on shortening the intake guide was cleared up to me when I spoke with a rep for Hot Cams. Some Raptors do not have the center intake guide pressed down far enough and some do. There is a little springy metal keeper that slips on the guide. If the keeper is flush with the head, then you are OK. I could see a guide to high causing the spring to bind creating a FUBR situation.