Author Topic: Bridgestone 90cc and 175cc Piston rings Interchange??????  (Read 4052 times)

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Offline Richard Clark BS parts

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Bridgestone 90cc and 175cc Piston rings Interchange??????
« on: February 26, 2009, 05:17:40 PM »
Bridgestone 90cc and 175cc Piston rings.

Piston rings for the 90 and 175cc Bridgestones have been long confused. In the past if you installed
wrong piston rings you would waste a cylinder and have to get a new one, no problem except for the cost.

Today with new cylinders almost being  gone it is now a BIG problem.

There are two styles of 90cc  cylinders: Cast iron and cast aluminum.  All BS 175's are cast aluminum

Rings and pistons for cast aluminum 90cc cylinders and 175cc rings and pistons are fully interchangeable.

Rings made for cast iron cylinders are NOT to be used in Alum cylinders for any reason, yes they will
fit, and that is the problem, many people have supplied rings made for cast iron cylinders to folks to use
in cast iron cylinders.    The problem is rings made for cast iron cylinders will wear out the cast aluminum
cylinders real FAST.

What is the difference in rings for cast iron and cast aluminum cylinders?

Rings for cast iron cylinders, are chrome plated cast iron.
Rings for cast aluminum cylinders are plain cast iron.

Reason is cast iron cylinders need chrome plated rings, and cast aluminum cylinders MUST  have plain cast iron rings.

Further  confusion is that the 90cc cast iron cylinders can be bored to oversize, in which Bridgestone did
supply oversize pistons and rings for these cast iron cylinders. 

The SR 175, although it is a aluminum cylinder, the bore size is a bit smaller, so these will not work
in any other Bridgestone,

In the end it is pretty simple:  If you have a cast aluminum 90cc cylinder or a 175   then your rings
need to be cast iron with NO chrome plating, correct part number is 1305-5010, but many rings have been
switched in boxes, so be careful. We recently bought a large inventory of new BS parts, we got many boxes of rings
marked 1305-5010 , but these boxes has the wrong rings switched inside.

Hope this helps  a bit

Richard Clark

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« Last Edit: February 26, 2009, 06:17:21 PM by Richard Clark BS parts »
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