Yamaha R5 Pistons

I'm working on some bikes I got out of a barn find. Essentially I got a Yamaha LS3, 2x 72 R5 350s and a 72 CB450 all for free. Right place, right time.

The LS3 is incomplete, missing engine. If anyone has one kicking around I would be interested.

The Honda looks like it will run, just de-rusting the tank and have to clean carbs.

The complete r5 is stuck/seized, I have not pulled that engine yet.
The other R5 has a basket case of an engine.


The cylinder jugs on the basket engine (and complete engine) are definitely R5.
But in the basket R5 engine, the pistons inside are just regular, non ported pistons. I was under the impression you needed to use the special ported pistons in this engine. Such as the wossner ones.

But then I look at the wiseco pistons online which don't appear to have the port holes.

So if I'm going to get one of these R5s running, what direction should I head? I'm not going for authenticity or original. Just affordable and running. Would like to make it a little scrambler bike.

For $300 I can get brand new Radjoot cylinder and piston kit. Essentially making the bike an RD350. Then I get better overall powerband, and I can rebuild the top end for $300. I would likely need to rejet, maybe not?

I can buy the wossner pistons, re-bore and put it back together.

I can hone the cylinder. Can I reuse the non ported pistons? Or is that likely what caused the bike to seize in the first place, wrong pistons?

All of these bikes have been sitting since early 80s. It's possible the good R5 engine is stuck, not seized. But after 2 weeks of oil sitting in the jug, it still won't budge. Have not tried tapping piston with dowel through cylinder head.

Thanks for any advice!

you must be talking about windows in the skirt on the intake side
if the piston has windows in the skirts or backside it is for a reed valve motor ONLY, simple as that,won't work in a non reed valve,piston port motor,no way, no how ,likely wont even start up
a non reed valve motor is called a piston port motor

These say they're for an R5, all years. They have the window

http://www.economycycle.com/servlet/the-560/Wossner-Piston-Kits-Yamaha/Detail

But the pistons I have, don't have the port in the side. That's where I'm confused. My engines are non reed valve engines.

those are not ports of any kind they are only lightening holes

okay thanks, then hopefully I have the right pistons. I was confused on the ports/no ports

the wosner and wiseco piston are forged unlike the stock cast pistons
the design of the forged piston makes it heavier than a cast piston thus they machine out some weight where they can

mikemehak said:

okay thanks, then hopefully I have the right pistons. I was confused on the ports/no ports

Click to expand...

not a port

confused on what should have a port and what shouldn't then

this is an rd piston with a windowed skirt, wont work in an R5

okay thanks.

Do you have any opinion on converting to an RD350 with a reed box, by replacing the cylinders,pistons? From what I read everything else was the same aside from jetting. But perhaps I read wrong?

as far as i know it is totally do able

Top end bolts on.
Don't know about alignment with the R5 airbox - you may need to use pods - and in the dark about how your exhaust system will bolt up as well.
Why not look at finding a blown up RD350 and swap in the six speed gearbox as well?
Pat

I ll be listening.