www.zxrworld.co.uk

got the engine out of the frame over christmas, was going to strip it down to clean up properly (currently pricing up bits and pieces that need replacing - shims, piston rings etc...

i'm planing on cleaning up the ports on the cylinder head, some light porting, nothing massive, is it worth skimming the head too while i'm at it? and also when do the valves need re-seating?

the valves need lapping if they leak when you run solvent into the air intake/exhaust ports, then need re-seating if the lapping doesnt work, or if there is damage to the valve seat.

as for a head skim, if the head is flat it wont need it, you can do it to raise compression slightly.

as for "self-porting", unless you are going to get it gas-flowed before/after, my impression was that with modern heads you could do a lot more wrong than right, as they are pretty much at max already, but if you are altering everything else, you might be able to boost the gas flow/mixture by altering the head profile, this sometimes means adding material back onto the head. also remember that incorrect/too much polishing can increase drag as you increase the boundary separation layer, creating turbulence and harming power delivery.

wicked advice cheers mate

i ported my RS125 when i had it and never had a problem with it, i spose being that theres more cylinders, more can go wrong etc...

Know this is a bit of an old thread but do you know what the maximum you can skim a head to? I've had a head gasket blow and the engineering company is being an butt