Single carb conversion

See

https://s3-eu-west-1.amazonaws.com/rgmnorton/fs/pdf/single_carb.pdf

I have a 32mm on an 850MkIII and it does lose a bit of oomph (technical term) but steady tickover and pickup on small throttle openings make it worthwhile.

Tony

I have a 1 1/8" monobloc on my Atlas (much the same engine as a '69 Commando). Goes just as well as when it was running on 2 of them. Might a 28mm carb be better suited?

Perhaps it was the setup I had, but when I fitted a single Mk.2 Concentric I always struggled to start the bike - the cold-start system didn't seem to introduce a rich enough mixture when kicking-over at the very low revs being generated by my leg. Tickling/flooding with the Mk1s gives a really good 'slug' of go-juice. I imagine this would not be a problem with an e-start however.

.. the right hand carb from my 850 on a Stewart(?) manifold. It worked very well. It may have lost a little at the top end but as I never went there I didn't notice.

I did try other alternatives including a Mk 2 Amal and a DellOrto (which was a nightmare as the throttle slide jammed in the body) but by and large was very happy with the single Mk 1.

On my ‘68 Atlas I use a 930 Mk1 Premier Concentric,on a Stewart manifold, provides easy start and regular tickover. 
Might be worth searching the forum to see previous posts about this topic. Just put single carb conversion or such like in the search box and away you go

cheers Simon

I run a 34mm single mk2 Amal on my 850 mk3. It cold starts really well, all temps, with choke. Choke straight off and hold the throttle to warm it up. Hot start, a whiff of throttle, no choke. It pulls really strong up to 6000 revs. I recently renewed my clutch plates, to stop it slipping in the higher range. Very happy with its performance.

Niggles:

- it's a tight fit to get a good run for the throttle cable into the carb. Doable, but care needed;

- there's not much room for a K&N filter, it chafes a bit.