I have partially stripped my MC18 (88/89 vintage) which is running with rs250 ignition and coils. It also has single ringed pistons. The pistons look o.k. but I would like to change the rings. It has only ever been used as a track/race bike. The Honda dealership reckons the piston is 0.5mm under size at 53.5mm and is having trouble finding the correct rings. Anybody got any suggestions as to what these pistons might be from or where I could get rings from? There are no stampings or markings on the piston anywhere.
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single ring is likely to be early nineties RS250 too.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks for that, have just managed to get a reply from tyga saying pretty much the same thing. Where in Swindon are you as the outlaws live in Eldene!
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Ah, just moved to Witney last month, so good spot - I'll go change my location!

Are yer folks bikers?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

No, not bikers mate VOLVO drivers!!!!!!!!!!!!!!!!!!!!!!!!!!!

I believe I have identified the pistons fitted to the bike, according to Matt at Tyga they may be RS125GP pistons and the bike may be running with a F3 crank. This may of course present problems with replacements!!!! but am still trying.
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xvfrona wrote: The Honda dealership reckons the piston is 0.5mm under size at 53.5mm and is having trouble finding the correct rings. Anybody got any suggestions as to what these pistons might be from or where I could get rings from? There are no stampings or markings on the piston anywhere.

The dealer has got an eyesight problem!

They cant be 53.5mm more like 53.95mm.
.5mm is about ten times the normal clearance.
If they are pre 95 RS pistons and rings you are out of luck as Honda dont make them anymore.
Your only hope is to find some old stock
or put NSR pistons and rings back in.
Good luck!

Yep, thats about as far as i have got. Latest measurements by way of calipers and micrometer are 53.975mm and 53.86mm respectively, both about as rare as hens teeth......UNLESS.......somebody knows different of course (or has a secrect stash of unused pistons and rings!!!!!). Maybe of course I should just try the tyga 300cc conversion.....unless the crankshaft won't take it!!!!!!!!!! doh!
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Forgot to mention I have cleaned up the crown and found the following markings : 5 AH IN. The locating peg is offset and there are NO markings by it! and obviously it just would have a 14mm piston pin and not 15mm.....bugger
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