YTM200 - Bottom Timing Gear No Longer Spins the Chain????

[mattb348]

I have a YTM200 that was running perfect. Today while my dad was riding it, it was idling, then died. Then when we pulled it over it had no compression.

We took it apart a little and found out that the timing chain was not even moving when we pulled it over. And the chain was still on the top timing gear.

I don't think it fell off of the bottom timing gear becuase it isn't nousy, and there is no resistance. It just acts as if the bottom timing gear is not even turning at all.

Anyone know what the issue is? And do I have to literally split the whole motor in two to get to it?

Luckily I have a spare ytm200 motor that I can get parts from, but I have a feeling this is going to be a pain in the butt to tear apart :)

Any help is greatly appreciated! Thanks!

[Yamaha_Rules69]

It sounds to me like the chain is spinning on the shaft that the gear is pressed onto, so it has to be off to either the front of the gear, or the rear of the gear. You dont have to split the cases to get to the bottom cam chain gear. All you have to do is remove the recoil, and there are 6? philips head screws holding the cover behind the pull start on. They tend to be a pain to get off, so be sure to have an impact driver type screwdriver and correct bit. You hit this impact driver with a hammer while twisting, and it usually works, and a little heat from a propane torch before attempting helps a lot. You have to get an socket extention with the appropriate size socket to hold the philips bit, because the screws are in pockets, and not flush with the case. You will also have to pull the flywheel, and behind that is the gear/chain. The other route would be to take the top end off, jug and head, and you should be able to get it back on the sprocket when the jug is off. If you take the top end apart, you should use new gaskets, and follow instructions in a repair manual. Good luck!

[mattb348]

Thanks for the info!

Luckily I have already had the recoil and the case behind it off recently, so I know it will come off easy.

By the way, to take the fly wheel off, do I need a special puller or anything like that?

Lastly, can I replace the timing chain by removing the recoil/cover, or will I have to also take the shaft that the small gear is connected to, out?

I think my timing chain is a bit worn out & loose. I could never get it as tight as it was supposed to be (as specified in the workship manual). You know how the rod inside the chain tensioner is supposed to go flush with the end of the tensioner assembly (where the small hole starts) right? Well, mine does NOT, even when I screw the tensioner in ALL of the way.

Also, when I crank the engine over, the timing chain always sounds as if it is a bit floppy, and it seems to jump around a lot. Do you think that is why it came off of the bottom timing gear?

I have another timing chain in my spare motor, but I am hoping that I wont have to split the engine to put the new chain on. Timing chains do not have a master link do they?

[cybrman]

I would suggest you get a new timing chain...running with an old worn out one is just asking for trouble if it jumps teeth on the gear....like new valves at least or worse a piston and damage to the jug etc...
There is no "quick and easy" way to replace it. You're gonna have to take off the clutches and other parts like the oil pump etc.. (at least on a Honda).
It is not all that difficult though....I always use the rope method (slide some rope into the cylinder through the plug hole to force the piston to stop and allow you to unbolt the clutches.
Just did one last night as a matter of fact.....now if I only had another cam gear bolt! What a pia finding them @ 7mm grrr!
Good Luck.