Hi new member. Have a 1982 3 wheeler 1982 125 or 175 but think it's a 125.
How many times can a cylinder bore be rebored? Can an already oversize bore be re-bored?
I got this machine in running condition but after I had it a few days I realized that it would require a top end re & re but didn't have time to investigate. Just yesterday I decided to tear it apart to have a look see. Well the piston and bore doesn't appear to be scored much or even badly but when it was together there wasn't much compresion either.
When I insert removed piston into bore is slides easily to the top of the bore, seems a bit to much clearance there? As well as seems a little sloppy when moved side to side. Rings don't feel like they have much tesnion or spring left.
Upon further investigation I noticed a number 25 on the piston, and on the cylinder bore outside a couple of numbers 3X300 and 123cm to the power of 3.
Apparently some fool before me decided to remove the air filter and ran without it. This is why this happens, bad for 2 strokes.
There is a decal on the faring of the machine which indicates a 175 Trimoto as well.
Hope some one can add some information.
Thanks.
Ron

 

wow my first atv was a tri-moto125 that was in 1981. i rode that trike every where. any way the stamping on the out side of the cylinder is just engine size, production #s, and such. 1t's a 125. you can usally bore them two over sizes, or two rebuilds. 25 should be 0.025 larger... sounds like to much cylinder taper and rings are shot. can you talk to a yamaha tech and see if you can get another bore out of it... hold on to that trike awsome piece of history.

 

look and see if wiseco makes a .50 over piston for your 125, I would take the cylinder to a machine shop and have it measured to see how bad it is, then they will know if .50 over will do it or not.