pistons and pin bushings

[wera racer]

I got the lower cases reassembled and back in the 78 GS1000 vintage racer. Then I talked to my machinest about the top end I dropped off.

Turns out I'm going to need new pistons and a bore job.

I see OEM pistons in 0.5mm and 1.0mm oversizes and Wiseco in 3mm and 3.5mm over. Any suggestions or does everyone just do the Wiseco overbore? Are those steel sleaves really thick enough to 3mm?

And how do you replace the piston pin bushings in the piston rod small ends? The machinest seems to think there's a little wear based on what he's seeing on the piston pins. I don't see small end bushings on the OEM parts fische, either. The machinest says he can't check the tolerances unless I disassemble the rods and take them to him. Can the bushings be replaced? Any suggestions on what to do? I hate to invest in a Wiseco top end kit only to destroy it because the small end bushings are worn.

Any advice will be greatly appreciated. I'm learning a lot and much still to learn.

Thanks!
Rick

 

[Nessism]

There are no bushings in the rods, the pin runs right on the steel. Your machinist should be able to use an internal bore micrometer on them to check for wear. The spec should be in the service manual. My guess is you would be fine if you use new pins.

Most people I've seen around here run the 3mm over, 1085 cc kit. The 3.5mm kit makes the liners too thin according to Big Jay of Ape, and he's a straight shooter so I believe him.

 

[wera racer]

Thanks, Ed! You're a big help...again. I never realized you could run steel on steel like that. Guess I've been working on too many two-strokes. So when the small end wears out you have to replace the entire rod? Bummer.

Yes, the spec is in the manual. Guess I can trailer the bike to to him to check the small end bores or maybe it's time I invested in a bore gauge.

Thanks again!

 

[7981GS]

I have a cylinder/.5 over pistons/rings/pins that I just took off of one of my engines showing 22,000 total miles on the bike.
For a fair offer plus shipping they could be yours.

Where are you located?

Daniel

 

[rapidray]

The pin ends of the rods don't really "wear". They CAN gall the pins or the pin end of the rod but the pin holes in the rods are easy to clean up with a small brake hone. The stock rods have no pin bushings & I don't think the stock rods have enough meat to put bushings in them. Also, the crank would have to be disassembled to bush the rods. Ray.

 

[wera racer]

Thanks, guys. I've ordered a top end kit and will run the rods as are.

 

[sharpy]

I know other people will abuse me but Wiesco pistons are made in china. (gudgeon pins are) Installed a kit in my fresh (28,000klm) engine and after 1000klms had little end knock on the inner pins. Got tool steel ones made from JE. Disasslembled and honed the little ends and still going stong after 50,000ks