Cam chain jumping teeth after rebuild. Is this common?

[barty5]

as title says is it common ??
Now over the years ive rebuilt countless 4Ts and to the day never had one do the just after being rebuilt. So long story made short took 05 crf250 in to shop to get valves re shimed all good job done. Take bike away for weekend it wont start properly check all sorts a things only to find timing is a tooth out corrected starts real easy. Spoke to said shop and they seam to think this is common. got me scratching my head cause it a 1st for me, Now i do understand that if the chain etc was streched its possible or worn teeth but they arnt crank is only 10hrs old and chain is in very good cond.

Me think shop is telling porkies my self.

[Jay GTI]

Was the ride the first time you'd started it since the valve work?

I've heard of cam belts jumping teeth due to wear or poor tensioning, but never a chain. Crap running because of chain stretching, or incorrect tensioning (even to the point of holing a piston because the timing was all over the place), but never jumping a tooth.

[ktm84mxc]

There's a thread on here for a CRF450 same prob the timing chain was out 1 tooth causing the same issues , seems its a common problem if you're not carefull in setting the timing/cam chain as the marks are hard to see.

[Dave89]

It is quite easy to get the timing one tooth out, but no the chain cannot jump unless turned over without the tensioner in, shop telling porkies.
They must have found it hard to start, or perhaps they didnt bother.

[FJRider]

Check out THIS site ...

http://www.thumpertalk.com/topic/639...chain-problem/

[barty5]

All the above where my thoughts as well they say that it was run before they dropped it off but problem was there from the moment we tried to start it. My thoughts where the same as stated and in that link that the tensioner wasnt released before it was started hence it started for them easy then released while running hence when i looked at it the tension on it wouldnt have allowed it to jump there just isnt enough slackness in it when released.

Should be interesting when they present me with the bill given ive spent over and hour resetting it and it stuffed a weekends riding.

[FJRider]

Don't get too vocal yet ... check the tension ... THEN ride it for a while. See if the problem reoccurs ...

[tigertim20]

as title says is it common ??
Now over the years ive rebuilt countless 4Ts and to the day never had one do the just after being rebuilt. So long story made short took 05 crf250 in to shop to get valves re shimed all good job done. Take bike away for weekend it wont start properly check all sorts a things only to find timing is a tooth out corrected starts real easy. Spoke to said shop and they seam to think this is common. got me scratching my head cause it a 1st for me, Now i do understand that if the chain etc was streched its possible or worn teeth but they arnt crank is only 10hrs old and chain is in very good cond.

Me think shop is telling porkies my self.

you are asking the wrong question.
is it normal? - as opposed to
Is this a common oversight made by mechanics?

[B0000M]

with the non retracting tensioner fitted to crf250's would that not make it a technical impossibility for the cam chain to jump a tooth?


i would have thought there would be no way it could possibly jump -- where's it going to get all that slack from?

[morg_nz]

i would say it was the same problem as my 450 - the person put it back together and did the timing but was looking from slightly the wrong angle and it was out by a tooth - i would also say they didnt start it in the shop. i think it is unlikely that they started it in the shop for two reasons - firstly, you found the fault first time you tried to start it - it seems weird that a bike would leave the shop in perfect condition where they had had it happily running and the minute you try it its not fine, and secondly im sure they wouldnt have passed up the chance to charge you extra if they found another fault when they were putting it back together

[barty5]

i would say it was the same problem as my 450 - the person put it back together and did the timing but was looking from slightly the wrong angle and it was out by a tooth - i would also say they didnt start it in the shop. i think it is unlikely that they started it in the shop for two reasons - firstly, you found the fault first time you tried to start it - it seems weird that a bike would leave the shop in perfect condition where they had had it happily running and the minute you try it its not fine, and secondly im sure they wouldnt have passed up the chance to charge you extra if they found another fault when they were putting it back together

this is my thoughts as well as for charging extra the cam has to be removed when doing the shims so personally I don't think it was started or if it was it was just by chance it started as it did for us a couple of times. Only other way i see it happening is the tensioner wasn't released before they tried to start it and it jumped as they started in guess ill never really know. Just really wanted others thoughts on it as they reckon it common but one hell of a 1st for me .