I have a 98 warrior that broke an exhaust valve. I had the valve replaced and now seams like compression or kick back is high. I've taken out 2 starting bearings. When it starts it runs good but just seams tight. I did develop cam chain noise and replaced thatnow I have this whinning noise when its running almost sounds like nylon gears not rod bearing noise. When I changed the valve I replaced piston and when apart the mains felt good still has anyone a clue?

1998 Warrior
Stage One Hot Cam
Full FMF exhaust
Open air box and jetted

 

anyone? One other thing I noticed while at idle it surges a little. Can I check lower end without disassembling?

 

Thanks for all the help guys I'd have been better off staying in the garage with a Miller Lite in one hand and my Toy in the other!

 

Sounds to me like it's not put back together right? Have you tried a compression test? Could it be possible the piston is in backwards, or the piston rings not correct, or was the cylinder bored exactly for the piston?

The noise could be coming from the timing chain rubbing the chain chamber in the head/cylinder. Are the front and rear cam chain guides installed and is the automatic chain adjuster working properly?

 

Thank you, I suppose the piston could be backwards and I only bought a replacement piston and rings I did not have the cy;inder honed because it was just done less then 6 months prior when the valve broke part of it lodged in the top of the piston also the head had some pretty good gouges in it. The cam chain tensioner id good aas well as the guides I do think I broke a little tab off the side of one of the guides when I took it apart though. The compression is 150 or better.

 

You are really supposed to have your cylinder matched to the piston. The new piston could be .001" bigger than the old piston. Not sure how much tolerance can affect performance, but it doesn't take much to screw things up. The gouges in the head shouldn't hurt anything, if anything, it might lower compression.

I think I would pull it back apart, replace the cam guide, check the piston sizing, and make sure the arrow on the piston is facing forward.

 

yea thanks pretty busy weekend hope to get to it next week sometime I'll let you know

 

I measured the compression its 170psi manual calls for 128max. I removed the head and did not find anything glaring at me. Piston is installed right and valves face is ok. Has some carbon on top of piston and valve face as well. I removed cam it is ok too. I removed jug rings are good moves in cylinder ok no marks on side wall. The wrist pin does have slop in it. It is very tight to remove from piston but inside connecting rod is worn some. There are crome plating spots rubbed off it. I did replace the pin with the piston. I can only think I have wrong base or head gasket that would cause my compression to be that high from what I see. The cam chain is new but the marks don't line up real good indicating the crank gear and cam gear are closer can a person get a thicker gasket like if they had head changed? When I rotate the cam to make valves open and close not connected to crank it is tough until it peaks on the cam then drops off easy because cam face is steep this is what I felt when I got the kick back is this normal I'm used to 2 stroke.

 

Mostly all of what you mentioned is normal. The cam mark never lines up perfectly, and the cam is hard to turn by hand. I can't see how the gasket could be a problem, although some people double up the base gasket to relieve compression, but that's usually if the head was shaved too much or something else on a modified engine. Are you sure the piston is not a .020" oversize and you have a stock bore cylinder? If you're not sure, a machine shop could measure them and tell what is going on. Sometimes there are numbers stamped into the piston.