Scooterotica

I've just fitted a GT186.

I have no head gasket (instant gasket instead) and squish is 1.0mm. this is an accurate figure as I measured 4 points at the same time.

Is this a little too low and would I be better adding a head gasket? I know it will be safer, but will I lose performance for no real reliability gain?

I've always told and been told squish needs to be 1.2 to 1.5mm

I know a few who've run as tight as 0.8mm. If you are confident that it's no tighter then I think that'll be ok, or alternatively fit a slightly thicker base gasket (+ 0.2mm on what you've used). Adding at the base gasket will increase the port timings slightly but that small amount won't do any harm.

case dimensions do vary a little, particularly Indian cases. Target squish is 1.2 - 1.5mm but they will run right up to 2mm. I'd check your base gasket thickness when it is compressed and maybe double up. I wouldn't get bent out of shape by the port timing changing if you add a base gasket because if the squish is 1mm then the timings will be 0.2 - 0.5mm lower than plan in any case.

Rather than doubling-up I'd suggest getting a pack of ally base gaskets in various thicknesses and using just one the correct thickness. AF Rayspeed do sets.

Thanks for help gents.

I hadn't considered the impact on port timings. We're not talking huge amounts here but I'd rather keep them higher than lower so I'll raise the barrel rather than the head.

Extra base gaskets ordered from the very helpful Rich Taylor.

I have just recently built a gt186 (not run it yet) my squish was the same I added a .5mm head gasket and when properly torqued it was 1.4mm squish