! Help Please :-) 2013 Txc250 Removed Timing Chain Tensioner On Accident

I will preface with “what was I thinking”!?

Working on my son’s bike to try and fix several items (Radiator fan / Bogging down at throttle /oil leak / starter issues) and for no reason other than to see what it was to we removed the (we know what it is now) timing tensioner to clean it but didn’t use the correct process of compressing the spring First before removal.
We put bike all back together and kickstarted and it fired up and ran fine for 10 sec before we started to hear a clanking noise and then it stopped.

Now there seems to be very little compression when cranking the kickstart by hand. And can hear the timing chain move with each light crank.

Any suggestions on what happened inside and what I need to put back in place?? (assuming we didn’t break anything else)

Thanks a lot!

Thanks for quick reply!

Popped the top off and ah ha! Somehow the top timing chain sprocket has popped out! Not sure really how unless we must have moved the bike a bit while tensioner was out which started the issue perhaps..

I’m surprised there can be that much play for it to come out of place unless I’m missing another part that has broke and is at the bottom?

Suggested next steps?

Maybe the gear was knocked out of position because the timing was way off after removing the tensioner? Either way, running or cranking the engine with the timing gear out of position means that your piston was moving up and down while your valves were stationary causing damage to the valves and piston.

I would suggest to take the head off and inspect the valves and piston and hopefully they are still fine. If so, reassemble the head and time correctly.

From the exploded part diagrams I cannot see any obvious parts missing. However, I think that the raised edge on the shaft should prevent the sprocket from moving outward. Maybe the bearings inside the sprocket are broken or the gear has shifted over the bearings

The snap ring on the picture below is not on your bike, but the shaft should look the same.

Much appreciated Sjiefke! If I were closer would buy you some Grolsch! (I was fortunate enough to make a couple of trips to Deventer for work and got to tour the Grolsch plant) You were right on the spot, the bearing broke apart and found the fragments at bottom of the engine sitting in the oil. I have new bearings on order. (Still scratching my head as the tensioner was installed correctly up against the poly guide, and looks like it’s hard to screw up! Hmmmm)

Also, if you get a chance, please see my other post for help on troubleshooting the starter as my 15yr son would love not to have to kickstart all the time! Lol

Best, Chad

The tensioner needs to be compressed before re-installation. If you remove the screw in the center of the tensioner and look in the hole there is a slot for a small flathead screwdriver. Turning the screwdriver clockwise will pull the piston back in. Install the tensioner without letting go of the screwdriver, put the bolts back in, and then let go. The tensioner will push against the guide and self adjust.

As for the electric start, the only things that have helped me are to replace the starter motor and upgrade to a Shorai battery. I also replaced starter gears, but my old ones weren't bad. Shimming the left side exhaust valve slightly tighter than spec will help the finicky auto-decompressor to work a bit better also.

Even after all that, it's hit or miss if the starter actually works.

Thanks a lot benny_mech for your direction!

Update: Was able to get new bearings replaced for the top gear timing chain sprocket and tensioner reinstalled as you described. However, new issue! Before I put the 2 timing camshafts in place I was able to manually crank the kickstart and it worked smoothly...but once I put the camshafts in place, with proper placement per shop manual, I went to kick start and it just jammed and wouldn’t budge any further...removed camshafts again and it cranked smoothly again...is it possible the valves are bad that is causing the stuck/jam/binding issue? And or something else to look at?

Thanks in advance!

Short answer; Yes....

Besides replacing the bearings, did you take the head off? Or at least checked the valve clearance?

It is ignorant to think that nothing got damaged when you ran it without the timing sprocket in place. At the least you might have a bent or broken valve. Please stop trying to start this engine without proper inspection...

Agree! :-) I will tear it down further and inspect the valves, etc. Will revert with pics...stay tuned..

*Curious* Any updates? *Curious*