Oversize rebore piston rings

[Chris Waddingham]

Hi guys - I am looking to help out a friend in South Africa get some rings he needs. We feel it It would be easier for me to get the stuff he needs here in the US (if available) and send it on to him. I will suggest that he registers on this site as well, but in the meantime - He is currently rebuilding two CB750K motors circa 1972 and sent me the following EMAIL:
"Hi Chris , ja thanks if u can check out for rings for a 63mm bore , compression ring thickness 1.5mm , oil ring thickness 2.8mm. Was a 810cc rebore at the time though checking it out now in ones old age and wisdom it's actually 785cc. Same as with the 900cc rebore it's 888cc."
And thats all the info he gave !! --- Strange charachter but I know that he is actually very knowledgeable about this stuff !! None of this means too much to me - I have always been a two stroke guy and have minimal four stroke knowledge. However the bore numbers (785 cc and 888cc) seem rather strange to me (are these common CB750 oversize rebores ??) Actually my question is this - I will be phoning him this weekend and will request further info - what further info do I need to ask him to provide so that normal people will understand what he is talking about and needs ?? and then how do I proceed from here.
Thanks
Chris

 

[dirtdigger]

63mm is an odd ball size. Good luck finding them, more than likely you will have to have them special made. 62mm is the biggest stock honda oversize and most aftermarket bigbore pistons started at 64mm which was the 812cc. 810 where usually named 811 or 812cc kits. 900 kits can be from 888 up to 915cc. Different companies badged there kits differently. Henry Abe made an actuall 888 kit though. Total Seal will make custom ring kits but they are in the $130 on up range. I talked to them about making some for some old 970 pistons I had, they will need very accurate measurements for ring diameter, ring width to be able to make them. Sometimes they will ask to have a piston on hand to measure themselves. Both of these sizes are not a common size anymore and the only place you may find them would be some new old stock that someone has on a shelf. If there are some markings on the pistons it would help in identifying them and help determine what actually they are. If you can get some pictures of the pistons and or any markings on the pistons I may be able to help in identifying them.

 

[Chris Waddingham]

Thanks for this info - I will pass it on to him - also will suggest he sends me a piston from each engine as sample.
Chris