1964 yamaha YM1

[makenzie71]

I just picked up a 1964 Yamaha YM1S...chassis is complete, no seat, and the engine is partially disassembled. I did a search for parts and replacing what I need to replace is too much. So now I'm thinking about what else I can do.

I want to swap in a simple 4-stroke motor. A single or a compact twin. I have a race-prepped 230cc Lifan motor I'm thinking about using...it'll kick out about 28hp, weighs 54lbs, and is very compact. I will need to get a carburetor for it and a couple other toys, but I can part what's left of the YM1 engine and make more than enough in return to do it.

So far I have $50 invested in the bike. I want to build a very bare-bones racer. As is usual with my bikes, I intend to do it without spending a dime out of pocket. I use what I have, the money I make selling unneeded parts off the bike, and what I can barter for.

Dug the stock lump and set a Lifan engine in the frame to see how it fits. I almost don't have room. Just barely clears the backbone.

That motor is a 150cc equivalent to the final motor...same dimensions, though. I'll be able to use one of the rear mounts in the frame and then I'll cut a set of plates for mounting the front up. It all should go together nicely.

Right now she's shaved 44lb between the lower motor weight, lighter exhaust, and battery box and such gone. Of course I'll gain a couple pounds back with my carburetor assembly and peripherals, but still a significant cut in weight.

 

[Erskine]

The lifan FMI is the OHV Honda CG engine that I've been playing with too.
I've ditched the starter motor on mine and got it running ignition only at the mo which is very easy to do. These OHV lumps are unburstable, loads of torque and mid range power.
And you can mend them with a spoon, some brown paper and a bit of string

 

[makenzie71]

That's what I love about them, Erskine. You may not get the same performance as a big-four motor, but are well built. It's just weeding the Lifans from the Zongshens and Shinerays and such...

As far as I've really gotten...did it while breaking some other bikes down (hence the bins in the back...full of bike parts). One of the bikes that came in had a spiffy set of Fox Sport shocks. Springs are rusted, but they swapped right over. Only about 1/4" longer than stock. They still have great compression and rebound damping. This winter I'll redo the springs...the shocks are rebuildable so I may go over the whole lot of it.

Also set the motor back in. I just went over the port and polish and lapped the jug and head. I tried mounting the thing to one of the rear lower factory mounts and thats just not goin to work. Set too far back and it doesn't center properly. Going to go back and use the front mounts and make some brackets for the rear.