I have a 2005 KFX 400 with a 2003 head in it. I bought with bent valves on it due timing chain skip. I replaced the big bore with a stock cylinder/piston and replaced with a head from a working quad. It started right up when i took it for a test run. Then a couple weeks later, i started it up, took it for a couple of test runs to 50% thorttle for couple laps around the house and started hearing a ticking noise. So I replaced the cam chain with a brand new one, replaced the chain tensioner (OEM), the exhaust cam and the oil pump gear that I observed was missing a tooth. The noise sounds is coming from the top end but i cant figure out what it is. I can only hear it when the bike is idling. when i give it gas it goes away; i dont know if it actually goes away or if i just cant hear it because of the engine. I am out of ideas. I've double checked my timing marks and the valves are within spec and compression is 115ish after 5 cranks. Could it be piston slap, decompression mech, other????

 

Just a WAG [wild azz guess]...........is the KACR intact, spring attached?



I'd think a mechanic's stethoscope would help isolate the ticking. Piston slap / wrist pin, etc would be picked up more distinctly in the cylinder rather than the head, I'd think. Keep us posted. Engine will run with valve cover off, maybe some eyes on will pick up the ticking offender.....

 

Maybe. Here's a video. Let me know what you think

 

I'm thinking valve noise......did you set the valves with the engine cold...

.010-.020mm intake

.020-.030mm exhaust

Shims are my least favorite valve adjustment method. Easy to get off a few thousands. If you kept track of what you used when you reassembled the top end, you should be able to feed the info into a shim calculator gizmo like this and confirm your adjustment is in spec.

Valve Shim Calculator

Either way, I'd pull the valve cover and do a looky see and check your valve adjustment just fer giggles. The tick sounds more like loose valve than KACR troubles.

 

Here's the update. I took the cam cover off and spun it by hand. I noticed a faint click from the decompression mechanism right when that half-moon metal elbow passed over the exhaust tappet. Now this was only at about 15 RPMs but my guess is it gets a lot louder with higher idling RPMs. The valve clearance for the right foot exhaust tappet was .009in/0.229mm cold. What do you guys think? Should I buy hot cams or can I fix this mechanism?

 

If you look at at the KACR, you'll see two rivets act as rotation points for the counterweights. They can be loose, one or both. The rivets are hard and tough to draw up, and I've never had any luck in doing that. Some have run their engines without the KACR successfully. Hot Cams won't have a KACR. Hot Cams will increase performance, possibly at the cost of longevity.