3 replies to this topic

Posted December 10, 2001 - 03:02 PM


Has anyone out there had
a timing chain break?
i have a 98 400 and am
considering doing one
over the winter as a
preventative maintanence measure.
am i being paranoid ,or
should these things be replaced

  • sirthumpalot

Posted December 10, 2001 - 03:07 PM


Speaking about 4-strokes in general (not this motor specifically), typically the timing chain failures that I have seen aren't broken chains, but are where the sprockets get worn and finally the chain slips a tooth or two. I would say inspect the chain slack, the wear blocks, the sprockets and the timing (stretched/worn chains can change the timing) and if all looks in spec then you're probably OK. Hopefully someone with more experience with this particular motor can chime in and add more info. Poor quality oil or extended periods between changes can really accelerate timing chain/sprocket wear.

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  • Shawbridge Husky

Posted December 11, 2001 - 05:12 AM


Torch, I have asked the same question myself in the past and Boit recommened that the timing chain be replaced with avery top end re-build as prevention. I did just so and upon removing the original chain found that it was kinking ( like the diagram in the manual ) This kinking may cause wear on the sprokets and load the binder also. Please replace it, it ia a 45.00 part.


Posted December 12, 2001 - 01:28 PM


Thank you Sirthumpalot and Hugh
for your input. $45 is a small
price to pay for peice of mind
this is one of those things
i guess you just have to weigh
out.im going to inspect it
and probably replace it.
Somtimes in the back of my mind
i wonder if a wear item
like the timing chain or
cam gear is gonna let go when im
on the face of a big jump.
I do take very good care of my bike
I change the oil every ride and
check the chassis and suspension torque
specs service aifilter ect.
but im new to 4 stroke mx bikes and
i guess im just a little nervous.
but i must say thumper power
deffinetly kicks some serious ass!

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