Measure bore diameter without strip-down - is it possible?

[rickm]

Hi,

Is there a reliable and accurate way to measure cylinder bore diameter without stripping the motor?
I presume you'd have to somehow stick some clever measuring device through a spark plug hole?

Thanks
Rick

[zed1015]

If the pistons are clean enough you may be able to stick a camera down the plug hole to read any markings on the piston crown or you could CC the cylinder and subtract the combustion chamber volume to find the capacity.
Other than that there is no special tool that fits through the plug hole and the head will have to come off at the very least.

[rickm]

Thanks for that.
I'm only asking because when I bought the bike (directly from Kipkawa) they said that they re-built the engine to standard capacity with standard pistons (NOS ?). However, a standard battery really struggles to turn it over and I've had to invest in a lithium iron one with much bigger CCA to get it to start consistently.
Guess I could do a compression check? (but then I'd have to buy a comp tester !)

[Julian_Boolean]

The pistons could be tight in the bores, or you could have a shagged starter motor, my 1170 turns over much like a stock motor now it's run in.

Taking the head off isn't difficult btw.

[ZedHead]

If the pistons are clean enough you may be able to stick a camera down the plug hole to read any markings on the piston crown or you could CC the cylinder and subtract the combustion chamber volume to find the capacity.
Other than that there is no special tool that fits through the plug hole and the head will have to come off at the very least.

Potentially, you could fill the bore to the brim with oil with the piston at BTC before the compression stroke. Devise some method of capturing all the oil that is squeezed out of the plug hole and measure the capacity.

Use this to calculate the radius, given volume and stroke, Double it for diameter

https://www.calculatorsoup.com/calculat ... linder.php

Good luck