LCGB Forums

new to this forum thing so bare with me
had a bog standard li150 s3 for about 15yrs now restored it myself with some help at the time and has run fine for all those years. the cylinder is now on its final oversize so i need to fit a gp150 57.0 (cant get hold of an li150 cylinder)
has anyone done this without changing carbs or jets?
or will the new gp150 top end run ok on a s1/18 dellorto with standard jetting?
also. top end shims or not? (again, standard italian li 150 crank)
hope someone can help.

My thought is that if you go to Wicksteed on Sunday, you will find about 20 Li150 barrels available. Expect to pay no more than £5.00. Buy a couple.

Thanks very much for your help I will look into that.
So I'm presuming putting a GP 150 top end on an Li 150 it's not a good idea

not that its a bad idea,just that if you want an li150 barrel to keep it simple they are out there.ask on here and the lambretta spares sites and no doubt someone will sort you out.

I’ve thought about your OP & reckon that if your crank is as good as an LI 150 crankshaft can be(!) it will cope with the GP150 top end, but you’d be wise to fit the corresponding inlet & SH2/22 carburettor. You don’t appear to want to consider over-boring what you have to a 175 which might amount to about the same performance.

You should be wary of any non Innocenti OEM barrel though, unless you like spending hours fettling.

Many years ago, I briefly owned a GP 150 with a de-baffled OEM exhaust & it was smooth, reliable, economical & quick without being too loud. I wish I’d kept it as it had a 200 front end as well....

Thank you to all those who replied to my question much appreciated your advice has been fantastic. I will be trying to get hold of the standard li 150 cylinder and won't bother with the GP top end at all.
Found an engineering company that does re bores for Lambrettas in stoke on trent so should be ok.