Motorcycle Repair: Use of torque plates, piston skirt, cylinder bores

Question
Hi Wayne,

Is it always necessary to use torque plates on a cylinder head when reboring (no matter if it is a single, twin, triple, four, etc)?

When the piston skirt (front and back of piston skirt side) wears unevenly is this possibly a sign that the cylinder bores were rebored without the use of a torque plate.

Thank you

Answer
Hi Edwin,

It is not too common for torque plates to be used when reboring small
engines as the cylinder is short and often has fairly thick metal on the
bore liner making it quite rigid.

The distortion even on a larger engine is slight (.001") but of more importance
due to the expense and complexity of reboring a multi cylinder.

Reboring can be done poorly or well even without using torque plates.
A poor rebore is often the result of abnormal piston wear.
Even without the torque plate some places still do a better job
of measuring and getting the bore straight.

I would suggest torque plates would have more effect on a three or four cylinder rebore.
The larger engines have more chance of distortion occuring and often
the bores will be very out of round.

A torque plate can be used just for the final stages of finishing hone
and will usually be enough help there.

A good boring operator can finish a smaller engine within correct clearances
and the torque is so low on the cylinder head studs that the distortion is not
very relevent.

If you are doing something like a Harley engine then torque plates are a good idea.

WS
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