Squish too large?

[PSC]

Hi,

I’ve just fitted a LML 5 port 150 kit to my 125 LML with an FA Italia head to suit.
The piston is level with the bottom of the transfer ports at BDC and almost at the top of the bore at TDC, which seems normal. With a 0.3mm (supplied) head gasket fitted the squish is about 3.5mm, which I think is far too much. The roof of the combustion chamber to the gasket face is about 2.8mm, which also seems a lot. Any thoughts/solutions? Ta

[holty]

I would machine the head to get down to 1.2 mm, you could machine the top of the barrel instead, but head is easier to do.

[PSC]

Thanks. Is it normal for Vespa heads to be so deep?

[holty]

I don't think its too much of an issue for vespas, but lml parts are made in india and are not made to the same high standard, that said ive got a mate with a 5 port 150 and it goes well, a little bit of lathe work will soon get your squish to a better size, a good machine shop should be able to sort it for you if you don't have access to a lathe.

[PSC]

I've had 1.0mm taken off which has improved it. I will run it like that for now and maybe take out the head gasket later to gain another 0.3mm.

[paul d]

I agree with Holty. 1.2 would be a good target. I always thought that a large squish would give a cooler running engine but that wasn't the case with my bro's polini. We were shocked at how much cooler a lower squish runs.