2-1 Amal MK2 manifold.... Norvil or RGM

Graham,

I fitted a RGM manifold for a single carb and it fitted perfectly.  The performance seems fine for me. 

You'll need a new throttle cable that has a 45 degree bend to bring the cable to one side to miss the top frame member, which is directly above the top of the carburetor. Also, I fitted a K&N filter onto my Amal Concentric.  Both of these are available from RGM.

Hi Graham,

I have the RGM 2:1 and an Amal MkII. This is on an 850 MkIII. 

Initially I had a 34mm but have now changed to a 32mm (2932/301) which is much better. Easier starting, smooth tickover. The 34mm was always lumpy at tickover whatever I did.

Happy with the performance, all fitted easily. Easy setup and no more faffing about trying to balance the carbs.

Tony

Hi Graham,

I fitted an RGM type to my Atlas many years ago and concur with all the above posts. If you go with the RGM manifold I suggest you apply thread lock to the two inner mounting bolts as a precaution in case they come out and are digested by your motor.

From memory I think the jets I used were 260 main jet and 106 needle jet. These jets sizes were published many years ago in RH mag by a member who tried many different jets and settled on these as the best for all round performance.

Andrew

Graham,

I used one of the existing 32mm Mk 1 Concentrics that was on my Mk3 as a starting point, with the intention of fitting a 34mm Mk 2.  But it went well enough for my needs on the 32mm carb, so have left well alone. 

A good friend helped me with the change to single carb as I had no experience of Commandos at that time, so didn't see what jets were used.  I'll have a look later today.

Philip

Graham, I forgot to mention that the jet sizes I mentioned were for a 32 mm Amal. I also fitted a brass slide as the carb i used had little wear.

Andrew

Graham,

If you do proceed on going up the 2 into 1 inlet manifold route, please consider lockwiring the two nuts (or allen cap bolts) that are done up on the inside of the manifold.

I have heard of several people that have had issues with these working loose and wedging the inlet valve open.

The main jet in my 32mm Concentric (Mk1) was increased from 250 to 270.  There was no evidence of the needle being changed, so I expect it is the standard size i.e. 0.106. 

I looked at the other carb that was removed and the needle in that one doesn't have any markings on, so the one fitted to the machine probably isn't marked either.  To inspect the on in the bike means removing the tank, and I don't fancy doing that at the moment!

Philip

try.

www.motocarb.co.uk

very helpful

Thankyou for this information Gentlemen, this may be the next job on my bike.