I bought a RVF400 a couple of years ago which had broken the chain and damaged the crank cases. I stripped the bike completely back then and I'm only getting round to putting it back together. I bought a pair of crank cases on ebay last year which were 'modified for racing' as far as I know the only way they could be modified is skimmed to increase compression???? But now I'm thinking "how doses that effect the gear driven cam set up"????

My plan was to rebuild my engine into the 'modified crankcases'. Does anyone have any opinion or see any obvious problems??

Thanks in advance.

Dont you skim the heads not the cases? I cant see whats modified to be honest, flowed maybe????

As for the cam gear setup, you just shim it to take up the diference.

Yes head skimming is the normal way to raise the compression but I was thinking it would be possible to skim the crank cases also????

Its the heads that be flowed/ported also, Dam modified crankcases!

Crankcases can be flowed also, or is that just 2 strokes im thinking of.

I really cant see what could be modified, im sure it'll raise its head once you start building the motor back up

The only modified crankcases i have seen are my Tony Scott one's All of the internal casting marks are removed,
This prevents the oil hanging on the sides,Making sure the oil gets back into the sump quicker.

weecorey wrote:Yes head skimming is the normal way to raise the compression but I was thinking it would be possible to skim the crank cases also????

Don't think there is enough to skim them as the pistons at TDC is pretty much flush with the surface. I have heard of lapping the the mating surfaces to ensure a true surface.

Crankcases typical are checked for trueness and the crank journals checked for alignment. Then (as others have mentioned) casting marks and sharp edges are removed.

Thanks for the repleys, so hopefully they be nothing wrong with them! I'm sure I'll find out soon enough. Need to get a complete engine gasket set now.