GP crank with Yamaha conrod

[Lamaddict]

I've had 2 of these done no grinding or shimming. The only thing to watch out for is it makes the crank slightly wider so check if you need an extra mag flange gasket, I never have. Both were done by Dave at Frontline (old motorbike shop), South Bank, M'bro. Dave does lots of work for local lads on Lambrettas and really knows his stuff.

So, he doesn't fit any big end thrust washers?

No he doesn't. I asked him about it and he said Lambretta's wouldn't need them.

Both cranks have been SIL ones and with the beautifully engineered yam rod they look great.

[Supereibar]

Mine touched the crankcase when rotating, so I had to trim the back of the conrod by a couple of thous. Other than that I just needed an extra mag flange gasket for mine. The rest was all fine.

J.

[boxofbits]

Any good for a rb 20 this crank conversion !!

[carlos fandango]

Any good for a rb 20 this crank conversion !!

Ive just done one for my RB20. Sil crank and a yam RD400 rod 115mm.
The std rod should be a TV 116mm, so the barrel will need 1mm taking off the base.
Russ

[Supereibar]

Russ, mine doesn't have any skim done to the base of the cylinder. Its more a matter of modifying the head I think.

Best,

J.

[carlos fandango]

Is it a RB20 Jaime ?
The RB20 uses a TV rod 116mm, so if you use a shorter rod, 115mm the piston at TDC will be 1mm lower and the port timings will be
different.
You could modify the head to take up the 1mm difference but the timings will still be different to std.
Russ

[RICSPEED]

You could modify the head

resesing the head is not a bad idea