balancer chain tensioner saga
Posted: Thu Nov 29, 2001 9:34 pm
Aware of the balancer chain tensioner problems, I was careful to
adjust the tensioner on my Y2K KLR often. Then, after a couple
thousand miles I began experiencing a chattering, rattling sound from
the left side of the engine when accelerating from low RPM. In any
other condition it sounded and ran fine. Being curious and paranoid I
investigated. With the alternator cover off I saw that the slotted
adjuster arm had a lot of free play with the bolt loosened. I took
out the free play manually in the direction of more tension and
tightened the bolt. Noise completely gone!
Now being more curious I remove the cover again and pulled the rotor.
The source of the adjuster arm free play was discovered. The arm was
loose on the D-shaped shaft which carries the tensioner arm. This
allows the tensioner arm to jump back and forth even though the
slotted adjuster arm is tightly bolted down. This jumping is worse
at low RPM under power when crank speed variation is greatest, thus
producing the chattering/rattling noise. This condition must be very
hard on the whole tensioner assembly. The play also eliminates
the ability to adjust the tensioner without taking the alternator
cover off. I decided something had to be done.
I saw no obvious wear on the adjuster arm or its shaft so I concluded
a tolerance mismatch had occurred and bought a new adjuster arm
hoping it would be a tight fit. No luck. It was just as loose as the
original. Not seeing another solution, I laid some weld inside the
adjuster arm's D-shaped hole and filed away until a light push fit
was achieved with no slop. 10K later the noise has not returned.
Clint