650cc '03 crank

johnyberg · Jul 15, 2015

I was wondering if anyone has ever machine a '03 32mm pin crank to fit in a 35mm pin. I think this would solve many problems such as crank spreading and conrod lifespan. The main advantage is the '05-'08 rod is 1mm longer. In that case we could use the 550 piston(23mm compression height), the squish now would be perfect and finally we have a high compression piston for our 650 engines!

bergbro · Jul 15, 2015

I discussed this with a couple of engineers when mine was apart last.....
not economical apparently. The crank webs on the 35mm pin will end up too thin and still not support the pin correctly.......
But I am not a trained mechanical engineer so am only repeating what I was told.

I would be asking why no one else has done this also?

johnyberg · Jul 16, 2015

I think the crank webs will be ok with the +3mm pin if welded after the assembly. I spoke with a mechanic and he said the tricky part is to size the crank webs at the exact clearence with the pin.

Taffy · Jul 16, 2015

I did this twice about 6 years ago. I used the 35mm pin in the 2001-2003 full flywheels. we calculated that the material left on the outside of the flywheel between the pin edge and the OD of the flywheels was 'marginal'. I never heard anything back good or bad from the two customers. one was a solo and the other was a Cannondale Quad converted from off-road to street by me.

there is never any trouble getting you the compression you want whether through a dme and lots of squish or the right squish but a flat piston or through both. I have an advert on ebay advertising such if interested Johny!

regards

Taffy

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650cc '03 crank

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