Topic: cb500-cb125s parts cross?

[kp751]

So i was referencing numbers on service Honda's' site and came upon something interesting and would like some thoughts. ....  BOTH 56mm standard bore.

CB125s piston code starts with 13101-xxx-xxx...same as cb500
CB125s standard rings..(what i need)  start with 13011-xxx-xxx...same as cb500.
CB125s piston pin...13111-xxx-xxx...same as cb500...

if I'm breaking the codes down right, the first set of numbers indicates the part it self.
the second set is the bike model it is used on.
and the third is the vendor or supplier number........i think.

So theoretically i could use 125 piston rings....i looks like the 125 uses a one piece oil ring....?   that OK.

seems that piston rings are more readily available and cheaper.

any thoughts or experience would help.
thanks guys
kp

[SteveD CB500F]

It would seem so. I've heard of this in the past.

Bryan will know! (when he gets in from work)

[bryanj]

Ta Steve!

all std pistons will start 13101 rings 13011
all 1st o/s 13102 rings 13021
all 2nd o/s 13103 rings 13031

And yes the middle 3 numbers are the "model code" whilst the last numbers can be manufacturer; supercision code or area code.

THIS DOES NOT MEAN THAT 125 RINGS WILL FIT 500 PISTONS
(unless the same three middle numbers are used).

It depends on the machining of the ring groove depths and widths which needs carefull measurement.

It does mean a COMPLETE 125 piston kit will fit in a 500 bore BUT the crown height may be totally wrong with not enough metal to remove.

There was one of the 125's in the UK that did use exactly the same piston but i cannot remember for certain the model (S or J I THINK!!)

Hope this helps if you have precise questions please PM me