OK. It's not a mini its a Blitz kit car I'm building, with a mg metro
engine in the back. ... But i've still got a real problem.
Anyhows, this 1300 mg metro engine is connected to an RC40 exhaust
system and a K&N conical air filter, camshaft is standard as is carb
needle (could it be this?). I can't get the thing to idle smoothly ,
it goes up and dooown, up and dooown, by about 300 revs,  all the time
(its a very regular variation). 2000 revs and up is ok . I've checked
compression, about 150 psi in the cylinders; i've checked and sprayed
for air leaks; i've stripped the carb. I've checked the valve
clearances. I've checked most everything, fuel, fuel tank....
Any suggestions, kind people, before I remove the head and check the
valve seating?
I've spent a long time trying to sort this one out, I'm desperate now.

Heeley C.