Bridgestone Motorcycle Parts Discussion Board

Bridgestone Tech Talk => Chibi, Tora, Taka Talk => Topic started by: CL-100 on June 09, 2022, 02:32:29 PM

Title: Pistons for Chibi engine
Post by: CL-100 on June 09, 2022, 02:32:29 PM
I've been going through my Chibi parts for an upcoming project and find that I have both versions of the 60cc cylinder.  One is obviously the early version as it is cast iron and the other is the newer version (much lighter and different exhaust mount) which I assume is aluminum.  The bore on the newer version doesn't look to be chromed.  I've gone through the Chibi parts manual as well as the 50/60 parts book and both manuals list the same piston/rings for either cylinder.  I've always assumed that the pistons/rings for aluminum cylinders are different from the ones for the cast iron cylinders. 

Does anyone know for sure?

Thanks for any help.
Title: Re: Pistons for Chibi engine
Post by: Chibi62 on June 14, 2022, 04:16:47 PM
Either piston will work for this application. The later and more common cylinder is cast aluminum with a steel (non-chrome) bore. Typically the upper compression ring is harden chrome, with carbon steel oil ring. If my memory serves me right - Pistons that have a recess dimple on the piston dome are used in chromed bore applications. There designed to handle heat better. Non-recessed dimple piston are standard carbon bore application.

Assuming the piston diameter is matched to the bore size (not bored over). You should be all set to run what you have.
Kevin   
Title: Re: Pistons for Chibi engine
Post by: CL-100 on June 15, 2022, 01:04:20 PM
Thanks for your response.  I've always thought that the pistons with the small dimple were for the non-chromed cylinder bores, while the 1/4" or so shallow swirl was for the chromed cylinders.  I appreciate you confirming that for me. 

I've got to find a standard size piston and rings for the new cylinder or a 2nd over piston for the iron cylinder.