GT186 Head

[srx600]

Hi, I have a GT186 kit which I plan to fit over the winter. There seems to be two cylinder head options, a matching GT porcupine head or a standard Li150 head. Its not clear to me whether the standard head would need to me modified to match the profile of the YPVS piston, is anyone using a standard Li150 head and is did it need to be mechined ?

[dickie]

You need to do quite a bit of work to a standard head to make it work. You'll probably save about 50 or 60 quid if you buy one and pay someone to machine it for you, but personally I wouldn't bother my arse.

[srx600]

You need to do quite a bit of work to a standard head to make it work. You'll probably save about 50 or 60 quid if you buy one and pay someone to machine it for you, but personally I wouldn't bother my arse.

Thanks, makes sense. I was told I could just bolt a standard head on with TV head gasket and it would be ok, it didn't sound right hence the question.

[dickie]

The 150 head has a recess machined into it for a 57mm piston crown, with a little extra diameter making it maybe 58 or 59mm.

The gt186 kit uses a 64mm piston.

I suppose with a thickish gasket and a slightly higher than usual crankcase mouth, you might just get away with it. But then you'd have a kit that wasn't set up properly and running below par, in which case you may as well have left it standard.