Posted September 6, 201113 yr Hey Guys, I have been rebuilding an RT1 360 for a while now and I am at the point of replacing the piston and rings. The cylinder wall looks good so I just want to put the same size piston and rings in but I am having trouble identifying the size of the piston. On the top of the piston, next to the arrow it has a #75 stamped in it. Opposite of that is #8025. Can anyone tell me if this is a standard (stock) piston or is it an oversized piston. Thanks!!!
September 6, 201113 yr #75 could mean .75m oversize? You can measure it with some calipers or take it to a machinist to check it. Gordo
September 6, 201113 yr Author after measuring with a micrometer.....the inside diameter of the cylinder is 80.35mm and the piston is 80.15mm to 80.25 mm. So I am thinking that this piston is a .25os. Now I know that there needs to be about a .35 or less difference between cylinder wall and piston. Would it be safe to say that this is a .25os piston....i dont want to say the other guys are wrong but I dont want to purchase the wrong size piston ya know!!! Thanks
September 6, 201113 yr I think you will find the guys are correct in saying it should be .75 oversize However are you sure the numbers are #75 and not # 25 Cheers TTB
September 6, 201113 yr Author I checked it again and it is a 75 and 8025 that is stamped on the top. I tried to post a pic on here but it didnt work!
September 10, 201113 yr What's 75 thou of an inch in mm? just under 2mm.... could it mean seven and a half thou?
September 30, 201113 yr Author Got the piston and rings in and the bike is running...thanks for everyone's help!!!
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