Yamaha RD60 help needed

[schmill]

Hi

Anyone know about these little bikes?

I have a 1975 RD60B that has the cylinder all scored up and will require machining. The bore should clean up to between 42.5 and 43mm.

I've seen 1st oversize (.25) and 2nd oversize (.5) pistons for sale but they never say what the pistons measure to. What was the standard measured piston for this bike? What size should I look for/be able to find?

I haven't seen anything wiseco for an RD60.

if I can't find a piston, would the jug from an RD125 or GT80 fit on an RD60? Did those bikes share any parts with the RD60?

Thanks!

[Vealmonkey]

You should talk to bandito90 on here, Timmy. He has an rd60 and the story on it is pretty amazing. We've been kicking around the idea for a gt80 top end. I have an aftermarket gt80 pipe and aftermarket gt80 large intake I keep trying to talk him into putting on. I'll try and find the stock piston size. There is a thread on here about his "POS 60" that tells more about his bike. I think the bike is posessed. If you would have seen how it looked when he bought it, well, it's pretty hard to describe. It had been layed down and the instrument cluster had been busted up pretty bad. Well, we just had to play around and got out the point file and did a little manual labor and set the points and added a little premix and it fired up! And one or two of the bulbs on the instruments actually lit up. Scary really. And the bike had the handlebars turned upside down to give it that "cafe racer" look. And the seat was a piece of plywood with a small cushion on it. And it had a front fairing and chin spoiler on it at one time that were also all busted up. The bike has come along way since then. Best of luck with your new project.

[bandito90]

Scmill,I would need to look at my shop manual to get get all the bore and stroke stuff.But I have been told by a few people that the gt/mx top end bolts up.I have one and have not tried it.This motor has been used in a variety of bikes.the basic bottom end was used in gt/mx 80,early yz80,yz50 and ysr50.I believe the gt80's were a speed vs the 5 speed in the yz motors.the gt80 and rd60 use a different stroke.I've read that the gt80 crank is what's used to stroke the ysr motor.I can tell you the reed blocks on the gt80 and rd60 are different.I would assume you could put a ysr top end on and have a better reed and carb setup vs therd60.Also I think the yz50 cylinder has better ports than the ysr .And it's alloy . Hope this helps.I'm far from an expert.But these are some of the things I know from researching on the net and talking to others.Here is a link to a more ysr oriented page. http://webpages.charter.net/jpcycles/ysrracing/faq.htm

[atc500x]

Pretty sure a yamaha JT1 mini enduro 60 use the same cylinder