Hitchcocks Forum

Hi folks

I'm rebuilding a 350 basket case Superstar and trying to get some modest performance improvement. BW has 'breathed' on the cylinder head, opening out the ports, blending in the guides etc, I'm fitting a higher compression piston, it will have a freer flow exhaust and filter, but I'm unsure which carb to fit. Has anyone tried a 28mm Mikcarb (as fitted to 500 Bullets) to a ported head 350? If so, what were the jet sizes and how did it go? Another option is to fit the 30mm CV carb originally on my ElectraX, but the mounting stud centres are too wide apart for the 350 head. Or should I bite the Bullet (sorry!) and invest in a 30mm Amal?

Thanks, Stephen

The 28mm Mikcarb has the same stud spacing as the Electra X CV...

If the head has been 'breathed' the carb size will be in some part fixed by the port size and the cams and compression, and what rpm you expect to use the most?


28/30mm Amal is the simple easy way to go, and jets are readily available. Main jet size will reflect the overall state of tune for the engine, (cams, exhaust, etc and port flow potential) but a 240 main would probably be a good starting point for the 30mm, but expect to drop down to 200 +/- with a 28mm

With a suitable flange rubber the VM28 Micarb should fit OK, try Allen's for a Mikuni item with 2" (50.8mm) stud centres, I'm pretty certain our hosts don't have them for the 350. Don't forget the tufnol spacer. Try it with the 500 jetting and see how you get on?



Another Amal option is the 389 1.125" (28mm) Monobloc for the BSA SS90 (tuned B40), which might be a good starting point. If I can find my Pitman manual I can tell you what that is! I know B.W. uses Mk2 Concentrics and could probably advise in that dept. Also consider the VM30 or even VM32 Mikuni option if getting a new carb.



A.

There's a Mikuni adaptor that bolts straight onto the 350 head and will accept either the 28m mikcarb or mikuni.

I don't know much about the mikicarb but I can attest that 1 1/8th 389 Monobloc goes straight on and with the appropriate jetting works perfectly. It also looks the part if that is important to you.