GT750 vs. T500 ring width

[Frank]

Hi Guys:

I'm reassembling a T500 engine (+.5mm oversize) and the piston rings I have won't fit the pistons! The pistons are from the GT750 but the rings must be T500 as they're 2 mm wide and the ring groove is less than that.

Does this make sense? I'm guessing I have to now find +.5 Buffalo rings to fit these pistons. Can someone please confirm ring thicknesses for me?

thanks,
Frank

[Frank]

I found the boxes and part nos:

pistons: 12103-31830-50 (was 12110-31712) and 12120-31002-050 (was 12120-31711 I think)

rings: 12140-15700

thanks

[oldjapanesebikes]

That part number for the rings is only for the early models ('68 through '74), with the older style T500 specific pistons. I think the current ring set part number you need, to match the GT750 pistons you are trying to install is 12140-30010-050. The old number was 12149-31719 if you find some NOS.

[Frank]

Thanks Ian. Do you know if the ring thickness for the numbers you mention is about 1.0 mm?

[oldjapanesebikes]

Thanks Ian. Do you know if the ring thickness for the numbers you mention is about 1.0 mm?

Sounds about right - you can confirm the part numbers at either the Alpha-Sports or Dillons Brothers web sites - I may also be able to post a photo in the next day or so of the two different types as I do have some T500 piston and rings as well as GT750 ones. I'd just have to find them.

[Frank]

Thanks for the link - very helpful. I'd been using another one that wasn't as clear. It seems pretty clear now what I need.

Frank