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Motorbike techs..... timing chain issues on TT250

Discussion in 'Technical and Troubleshooting Torque' started by Gus The Snail, Jan 26, 2008.

  1. So i got another TT250 ( this makes 3 ) complete , partially re-assembled , wasnt turning over properly , so i checked timing and it was out , but the chain is unbelievably tight.. even with the tensioner out , i got the tensioner in , but its now so tight its hard to kick the motor over.

    Its a fairly new motor ( unsure of how new ) so i was told , and cleanliness indicates that it may be , oil filter did have some metal dirt in it ( from what, i have no idea ) but everything in the clutch section looks brand new.

    My main concern is the chain.. its way too tight , i need a few opinions on why this would be. I have a manual for it , but no-where in it does it have this problem. ( also have a repair manual on cd bought from ebay )

  2. Interesting ...

    Sounds to me like you need to check that the camshaft is moving free in the head as a start. I go here first because you mention the metal filings in the oil filter and the cam runs directly in the head rather than on roller bearings. IF the chain is as tight as you say it wont be long before it snaps and coils itself up in the bottom end causing a sh*tload of potential damage.

    Take the tensioner out and see if you can drop the chain off the cam sprocket then check to make sure the cam turns. (much easier if you take the spark plug out as you wont be getting compression) you can also make sure the bottom end turns freely without the head operating to try and isolate the problem.

    Definitely seems more likely to be a problem in the head than the bottom end.

    Good luck

    (using my partners log in)
  3. Thanks for the quick reply...

    Cams turn freely , the timing was actually out on the intake valve , but this wasnt the problem. We got it running with no tensioner , it doesnt rattle or anything , but im guessing thats because the chain was/is so tight.

    Im beginning to think the chain is a link or 2 too short for it
  4. The bike isn't running an over-thickness head gasket is it? unnecessary gaskets on the cam mounts? if not, you're probably right, the chain is too short. It isn't being jammed on a chain guide? are all the chain guides installed correctly?

  5. dont think its got oversize head gasket on it , doesnt seem to me to be overly thick.

    Not jammed on anything , like i said , got it running , no noises from motor , runs quite well , but having no tensioner is a bit worrying
  6. Counted how many links versus the other two? see how it goes.
  7. still cant work it out.. nothing is overthickness , and keep losing count of the links ( and my temper in trying ) , so im going to make up a spacer to put between the tensioner and the barrel , at least this will plug the hole if anything!

    Cheers for all the help
  8. Use a dab of liquid paper on one of the links. Use a second dab every 20 links and so on. You might have to wipe the oil off the link first...


    Trevor G