Cam Chain question. 99 XT600E

[pursang]

I'm doing a top end piston replacement.

Besides the cam/crank being synchronized I was wondering on the XT600 does the cam chain need to be in any particular position on the gears ? like with some automotive applications where the chain is marked and corresponds to a mark on the cam gear.

Also is it possible to re-install the cylinder by carefully keeping the cam chain snug on the crank gear while passing it up through the cylinder ? I'd like to avoid removing the flywheel cover.

 

[Bugsinteeth]

Hi Pursang,

My XT600 is a 1986 and I have more experience taking it apart and putting it back together than I care to admit! I recently did as you propose, top endremoval without disturbing the bottom end.

Some things to consider.

Prior to disassembling the cam/cam sprocket/chain assembly. Carefully and logically lay out some paint marks that can get you back to the same spot. The engine needs to turn to dissassemble the cam, but as long as you keep track of which way you have moved it and also kept the chain taught on the crank......every thing should line up in exactly the same location once you button the thing back together. Note there are timing marks on the cam sprocket that will be evident at TDC on the compression stroke which is where the engine should be located for disassembly. If you add a few paint marks as described and maintain the chain to crank relationship you will end up with visual evidence that the parts are back in the correct location and the engine is timed correctly without needing to see the lower timing mark situated behind flywheel in the bottom end.

There are many ways to screw the above proceedure up, as I'm sure you know. So don't screw this up!

Carefully make note of the angle/placement of the front camchain guide upon disassembly. The bottom of the front guide sits in a little cradle shaped Uthat you will not be able to see upon reassembly (it's in the bottom end behind the flywheel).

How many clicks are showing on your cam chain tensioner? If lot's this conversation is redundant. The stock cam chain is the endless type and the flywheel will need to come off to change it. Non endless chain not recommended, Pull the flywheel and do it right!!!

Inspect the little end of the rod. If the copper coloured finish where the piston pin sit's is worn away. You will need to redo the rod. That means a full teardown.

Attempt to shine a light into the bottom end and inspect the condition of the visible transmission gears. If they show signs of being chipped, and you would like this machine to last a long time, ....... again..........you will need to do a full disassembly. Gearbox chipping is what kills most XT's

Good Luck!

Bugs

 

[Bugsinteeth]

Just another note:

I like to use a socket (19mm for XT) and breaker bar combination (not ratchet!) on the end of the crank.

I then wire the braker bar in position at TDC so the crank doesn't move during work. When it is time to move the crank and chain assembly back and forth as needed the breaker bar has much better control than a rachet = Less chance to screw up timing.

Cheers,

Bugs

 

[pursang]

Thanks for your advice Bugs I appreciate it ! at this stage it's too late for marking the chain but I'll remember to do that next time, the chain tensioner is showing some clicks but without checking a manual I'm not sure if it's maxed out, the small end of the rod looks real good as does the piston pin, nice and smooth with no heat marks, couldn't really get a look at the trans gears through the crankcase but I'm not finding any evidence of broken parts or excessive wear, in fact I'm surprised at just how clean the crankcase is, it looks brand new. I measured the rod big end for side clearance it's well within spec.

Good tip on using a breaker bar on the crank, thanks for that.