From:Dr. Pepper
Subject:RE: 165/175 jug, etc. Date:Sun Oct 16 08:49:18 2011
Response to:16456
Chuck, The jug,piston,rod,head are the same size,the later rods have needle bearings and can't be rebuilt and early one have rollers.There is a spacer that is used on the 175 to compensate the longer stroke,it goes under the jug~~without it the piston will hit the head.If you take a 175 and put 165 flywheels in and leave the spacer out it should make it a stock 165 with no loss of compression and the other way is to take a 165 and put 175 flywheels and the spacer in and then its a 175~~~Am I correct Mutt ?
See picture of spacer,I found this out the hard way when I did my motor

Since the 175 has longer stroke, how about the 175 cylinder height? How about the 175 cylinder head? My 175 was destroked with more available 165 flywheels during a rebuild, and wonder if it lowered the compression in the original cylinder? If so, how about milling the head to compensate?

The 165 175 have the same bore, the 175 has a longer stroke.

I need to replace the pistong rings on my 1963 175BTH motor. I can only find listings for new 125cc and 165cc rings on sites such as Are the piston and rings in a 165cc and 175cc the same?