Topic: Measuring piston/cylinder clearance

[P.abrera]

Not quite sure if i understand the concept properly here but if im looking for .025 clearance. I should be able to squeeze a 0.025 feeler guage between one side of the piston and cylinder, yes?


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[Bootsey]

From my understanding you really need bore gauges/micrometer to measure both the pistons and bore. You need to know that the bores aren't tapered or out of round. Probably does depend on whether you are reboring or just honing and reusing old pistons, as to what level of accuracy of clearances you'll be looking for.. Also the pistons are often a different size at the top than they are at the skirt.

[Garage_guy_chris]

I think you missed a 0 i would think 0.0025.   a feeler gauge is not the correct tool to use you would use a micrometer (on piston) and telescopic bore gauge (on cyl) or micrometer (on piston) and a bore gauge (on cyl). then subtract measurements for your clearance's. the piston skirts are also tapered and or cam ground so you need to know where to measure them You also have to know how to use the tools properly or your measurements will be way out of whack and not make sense.

[P.abrera]

I think you missed a 0 i would think 0.0025.   a feeler gauge is not the correct tool to use you would use a micrometer (on piston) and telescopic bore gauge (on cyl) or micrometer (on piston) and a bore gauge (on cyl). then subtract measurements for your clearance's. the piston skirts are also tapered and or cam ground so you need to know where to measure them You also have to know how to use the tools properly or your measurements will be way out of whack and not make sense.

ahh, looks like im in over my head. Best left to the to the pros methinks


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[dave500]

bootsey and garage chris are right on,if you can take it apart then take it down to an engine rebuilding place with the factory specs and tolerances, theyll size it up in no time,be sure to write the specs down clearly for them,these are an old bike and most shops now wont know what a Honda four is?you might need to shop around to find one who;ll be happy to have a look at it?

[754]

Feeler guage can be used to get wrought to idea.
 If the clearance should be. 002,  and you can get a. 005 in, you need a rebore.
 Measure only on the skirt, 90 degrees from the pin.
D
Not super accurate, won't reliably tell you how much taper, I or out of round.... But if you establish that it needs overbore, you saved a trip to get it measured.