Cam Chain Binding after Valve Clearance Work

[LaserBeam]

Bike Model = : GT250R

G’day guys. The Front Cam Chain is BINDING after i removed the cams. I also put a new gasket on the Stator Cover & thought the IDLE GEAR SHAFT had come loose & that the Starter Idle GEAR was moving around. IT WAS, but i drained the oil & fixed that. But i still have the binding. The Front Timing Chain is SO TIGHT i had to remove the bolts of the Chain Tensioner to give it some slack. Then i turned the motor by hand & the Timing Chain is SKIPPING/JUMPING over the Front Cylinders INTAKE CAMSHAFT. Literally skipping with a jolt. It’s like the Cam Chain has 2x Links stuck together & NOT gone on corrrectly, even though i count 16xPINS between the Intake & the Exhaust cam.

I’ve spent 4 full days doing new oil, filers, gaskets, plugs, then valve clearances, only to end up with TIMING that keeps going on it’s own. The Timing CHAIN must be jumping off, & not rotating the camshaft, for it to go out of sync.

I’m worn out. 4x full days work, 4x removing the front & rear camshafts, another week of not riding. It’s hurting me badly. Any ideas of what could be causing the cam chain to bind so tight & jump off the cam as i rotate the engine?

I’ll drop the cam chain off from the TOP & see if i can get it back on with a magnet. What else could it be? I am exhausted. I hope you guys have some ideas for me. I feel like crying but i’m too dehydrated from working in the heat. PLEASE HELP. Cheers.

-----LaserBeam---->

[♠️ M77]

Hey, this sounds like extra hassle but i hope you don’t mind it,  remove the whole flywheel.

I had this issue with a customer bike in the UK that was a 125cc variant, the bottom crank shaft had 2 missing teeth which was a known for certain engine batches, so the chain was never fully wrapped around and didn’t run right, eventually the front cam shaft snapped in half.

So have a look at the bottom crank teeth where the chain rolls and confirm it all looks good and healthy ?

If so, do you want to chance a replacement cam chain and cam shafts and tensioner ?

Take a look at the tensioner Belts (the plastic guides that slide the chain , including the top metal triangle which has a plastic buffer that gives the chain some little downward tension also)

It’s a good job you have sharp ears and eyes, it could have been worse and fortunately it sounds like either the chain or the tensioner need a replacement  (IF the crank teeth are OK or  the cam shaft Teeth are also OK? – giving the sprockets no-reason to jump the chains at high speed)

You’re lucky, a single chain bounce out of the sprocket,  over here means were are rebuilding a snapped engine🤕🩼

Let us know what you find!

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