TR 280 BB Install, CCT issue

I have a 2008 yamaha wr250x with 5,000 miles. I have just finished installing a thumper racing 280 big bore kit on it.

When i first fired it back up assured that timing and all was correct, it started up instantly as seemed to be running fine but i had quite the tick coming out of the chain area. I spent the weekend double checking everything and reset timing to be absolutely sure something was not off. When i fired it back up it had same noise but after running a couple minutes i could bring up the rpm's a hair and let off and it would sound normal so it confirmed its not a valve tapping a piston or anything of that nature, i could actually let it idle for 10 minutes and never hear the noise but as soon as i rev it just a little i get this clatter that sounds like a chain bouncing back and forth. Now the CCT on my bike is held tight by oil pressure that i know i have and cct was filled each time i removed it. When i first started to tear the motor down i removed the cct and set it to the reinstall position of being locked down. It sat on my bench for a little over 2 weeks before i had everything to reinstall the motor. Is it a likely scenario that leaving the cct in the locked position may have jeopardized the spring inside. Like i say it idles ok sometimes the noise being there and other times it would completely disappear but if i raise rpm's slowly it comes up a little then its as if the tensioner lets loose and it starts clattering. Anyone think this a likely failure of this oem CCT? Any input or opinion would be great, i've about pulled my hair out this weekend trying to sort this out.

I've had experience with manual cam chain tensioners on some kawasaki 636 motors and this sounds like a loose chain type of tick and chain bouncing but just trying to find other opinions. Gonna order a Kreiger manual cct as it is a great option anyhow i'm just hoping it resolves.

Just curious if anyone has ever heard something similar, it was scary at first thinking I may have a piston hitting a valve but its deff not. Everything seems ok there and when the noise isn't happening the bike sounds absolutely flawless.

I think I would change the CCT. My Yamaha snowmobile is a 05 and they had problems with them. They were not recalled but close to it. If the CCT were to fail and the bike jumped timing would be catastrophic to the engine and your new big bore kit. IMO I would put a new one in just for a piece of mind.

Quote :

Cam Chain Tensioner

Everyone that has an RS sled with the old style tensioner should replace it BEFORE it fails! If it fails your engine is shot.

Mine died at 4000 miles. Yamaha would do NOTHING for me. This does NOT speak highly of Yamaha.

Replace your tensioner now. Yamaha does NOT have the courtesy to contact customers and make them aware.

This is from my TY4stroke forum. I don't know if there has been any issues on the bikes but would for sure ask a Technician.

I've already emailed them to see if I can order a manual one to try, I wont be running it until I get that replaced, I haven't heard all that much about failures with these bikes tho, that is what seems very odd. But there isn't much else that it can be for what i'm hearing anyhow.

Just a report back on this, it wasn't the cct altho I didn't mind adding the manual one anyways. What I found was one of my intake valve shims had jumped up out of the hole on top of the valve and was resting on top of the valve washer, this was allowing my piston to just barely tap on my valve as it was returning upward and piston coming upward at same time. Fixed the shim and all is fine, runs like a top and I can feel the added power of the tr 280 kit so im confident I didn't do any damage to the valve that was lightly being tapped. Not sure how it ever happened as I never once lifted the bucket on the intake side, only thing I can think of is either when lifting the camshaft off the bucket it stuck for just a second and allowed the shim to move over. I know from now i'll be double checking valve clearance before placing the cover back on. Stupid mistake on my part but glad I figured out before damage was done.

Good to hear you found it.