Has anyone had any experience with these carbs?

I purchased my 40PHH Twins jetted to suit an A15 stocker with a little cam work.

I have them on my worked A12 and I'm having trouble getting them to behave properly. At the moment I can't get them to idle consistently, it sounds like when they're idling there isn't enough fuel and they slowly die out unless I flick the throttle.

I haven't properly synchronized them at the moment as I can't even get them to run consistently to test (using the old school pipe-to-ear technique).

I understand the Pilot Screws (idle mixture regulates air-fuel mixture ratio during idle) are pretty important, what are yours set at? Mine are 1 and 1/2 turns out from seated.

Can anyone please help?

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  Twin 40s.JPG (129.51 KB)

Here is a quick video showing what I'm trying to describe.

Idle then Fuel Starvation?

what kind of fuel pressure do u have. maybe to much or not enough.

Mornin Bige,

Yeah fuel pressure is stock off the A12 Facet pump. But I have left the tap in from when I had the bike carbs on so the inlet and outlet of that are pretty narrow so I might pull that out and give it a go.

Problem is you need a base to start tuning these things and at the moment I can't keep the thing running for long enough.

When I had the hose to my ear on the first carb I heard a distinct knocking/popping sound, does this mean my tappets are out?

Can anyone also explain the carb backfiring?

I'll have another go at it.

check tappets.it could be a lean pop/knock . try a electric fuel pump with adjustable pressure reg. cheers

So I removed the little tap, I think that helped.

The stupid thing was I had the front Jacked up, at least now I'm on a level!

Had a play with the Pilot Screws and it's running better, hopefully get it on the road soon.

I reckon that popping definitely is the tappets. I'll work on em now.