Quote:1200/A12 GX head sounds the go.
Smaller chamber for more compression, ........ check.
Bigger ports than A15 for more airflow, ........ check.
Double springs for more revs, ...................... check
Smaller valves than A15 for more economy [???] ........ check.

wow; I get about 6300 out of mine before the valves float; never tried to push it past that......don't feel like replacing it.
hell even with two dead cyl. #2 #3 it would rev to 6300.....

1200gx head would be the go tho wouldn't it? Hi-comp/bigger ports?
And yeah i do james but... It looks pretty much the same as it did before haha

Got any pics of the A15 in the 120y.

My A15 shouldn't be to far away from being built.
Can't wait

Stock A15s are good.

A15s with A12 heads are not likely to put out as much power at high RPM. Keep it stocker. On the other hand, you'll probably get better fuel economy....

ha yeah, i figured it was the head, its only there because the a15 one has bad valve stem seals and i needed something to get it going, without blowing a heap of smoke, i might have to smash it back together with the a15 head. cheers

were the a15's really that bad stock? i don't remember it sucking that bad, but now it's anything but stock, and i don't remember what stock was like...

Perhaps you're using an S-flow silencer, which comes stock in a 120Y I removed mine to straight flow and my stock A15 can rev up to 5k rpm, even on 3rd gear.

But swapping the head to oval port shud solve your problem too.

Yes, if it has a round-port A12 head, I wouldn't expect the A15 to rev over 4500 rpm ... like sucking air through a straw...

I wasn't sure about the exhaust, the one on the van i pulled it from looked to be the same.. Cheers
Also. It wouldn't have anything to do with the round port a12 head would it?