Single Carb conversion

Shaun,

I run a single 930 Amal on my 650. recently i acquired a manifold to do the same on my commando. i prefer to keep a british carb on my british bike.I do have the brass sleeve modification which makes the carb perfect. I use the stock aircleaner set up (single carb Atlas). you can pick up that breather vent right at the oil tank and run it into a can or on the ground or modify the stock aircleaner to a single hole and leave the breather venting into the motor. usually makes a mess of things ... Only one cylinder draws gas at a time so one carb issufficient unless you are dragracing,i that caseyou wont have enough gas flow into the single float to keep up with enginedemand. Normal riding you willenjoy the simplicity. IMHO

Steven Phelps

Hi Shaun,

I got my mk2 amal from RGM, with the manifold and k&n filter. Once it was set up it ran fine and I took the choke lever etc off the handlebars.

I have got through a couple of floats on the carb in a year (both full of petrol) and have suffered blocked jetsetc but this is just bad luck? I got someone in the club to fit it after i failed miserably as it turned out to havea casting fault (to do with the choke circuit apparently).

Rgm were very helpful in all this though. A lot of answers on this subject on www.accessnorton.com a commando forum I found one quiet workday afternoon seem to go for the mikuni but I had trouble finding a kit that wasn't 2 1/2 times the price of the Amal.

With hindsite I might go for the mk1 route as they are such a cheap and simple carb, but my 2 mk 1's were both a bit worn.

The latest problem to affect the bikes performance is a broken garage door, I can't get the thing out of it even after getting all ready for the spring!

The Mrs thinks it' s cursed!

Mike

Previously wrote:

Hi Shaun,

I got my mk2 amal from RGM, with the manifold and k&n filter. Once it was set up it ran fine and I took the choke lever etc off the handlebars.

I have got through a couple of floats on the carb in a year (both full of petrol) and have suffered blocked jetsetc but this is just bad luck? I got someone in the club to fit it after i failed miserably as it turned out to havea casting fault (to do with the choke circuit apparently).

Rgm were very helpful in all this though. A lot of answers on this subject on www.accessnorton.com a commando forum I found one quiet workday afternoon seem to go for the mikuni but I had trouble finding a kit that wasn't 2 1/2 times the price of the Amal.

With hindsite I might go for the mk1 route as they are such a cheap and simple carb, but my 2 mk 1's were both a bit worn.

The latest problem to affect the bikes performance is a broken garage door, I can't get the thing out of it even after getting all ready for the spring!

The Mrs thinks it' s cursed!

Mike

You can have the Mk 1 wortking better than new "Bruce Chessell expertly machines the bores of Amal and Bing slide carburetors to bringthem back to exactly round and perfectly smooth. He then takes your old slide turns it down and re-sleeves it with a brass sleeve. The sleeve is then machined to the exact size and tolerance for a perfect fit in the carb body. This will repair the corrosion and galling that can occur over time. The slides in the carburetors will operate more smoothly and work more efficiently."Only problem, bruce is in Ontario, is this not done on the other side?I have this modification, the carbs are better than new, you dont even have to go the single route . no airleaks, smooth idle, just a little more time synchronising everything.

Thanks Steve,

The door is a henderson type thing with a big spring- the repair bloke is due out Wednesday as i can't do it on my own and just want it sorted properly.

A new set of cones and cables should sort it i hope.

Previously wrote:

Thanks Steve,

The door is a henderson type thing with a big spring- the repair bloke is due out Wednesday as i can't do it on my own and just want it sorted properly.

A new set of cones and cables should sort it i hope.

I have a 34 MM mikuni kit that I'm selling on behalf of a friend who has limited access to the internet, See my add in the classified section.

Previously wrote:

I'm thinking for practicality of changing my 1975 MK3 to single carb. Some people recommend a 36mm Mikuni, others a 34mm Amal MK2. However, I've also been told that the cheapest option is to buy a single manifold and use one of the existing Amal Mk1s (albeit rejetted). I'd like to hear from anyone who has experience of any of these options.

If I can use an existing MK1 that would be great, especially as when one wears out I'll still have another.

Only downside is that to buy an airfilter from Norvil will set me back over £160! I'd like to know if I can safely use an ordinary K&N conical or even a pancake type filter (as fitted to my Bonneville).

Also, what to do with the bizarre breather assembly from the oil tank to the airbox and carb manifold. Presumably, I would have to vent the tank via an ordinary pipe out to the side of the bike, as for example on a BSA A10?

Any advice gratefully accepted!

Shaun from Headcorn

Hi Shaun - I have a Mk2A 850 rebuilt as a 920 and fitted a single 36mm Mk2 Amal Concentric via a RGM Manifold thinking that a 36mm on a 920 would be about right - it turned out to be too large and rebuilt the carb with a 34mm Body (false economy as it turned out as it cost me as much in parts as buying a complete 34mm carb). However it now runs fine - the 36mm always ran too rich and starting (especially when hot) was always a bit 'flaky' . The air filter is a fine mesh gauze thus the jetting I have may not suit a carb fitted with a K&N etc.

With regard to the breather setup I fitted a one-way valve on the crankcase-to-oiltank line (valve from Les Emery) and then a 5/8 inch pipe from the oiltank to the rear of the bike - this works OK but I do tend to get odd drips of oil deposited out of the pipe after a run - my wife's not happy as it messes-up the driveway !.

Hello there, I'm a new member with a '76850 Commando ES; but I previously had a '75 850 that I didaKeihin single carb conversion on, it was a good while back now and I can't remember the actual size of the carb, but I did put in on a rolling road and we could not for the life of us get it to rev past about 4,500 rpm. At this point it was delivering 50 hp, and 50ftlb! However it was a Norman White engine rebuild and was not at that time fully run in.

The bloke who ran the dyno., said that he had seen this before and that if i wanted it to run properly I should use a vacuum fuel pump from a Suzuki SP650/DR650 (?? - not too well up on them), as it does not fit in the tank and can be sited externally and was easy to fit.

Never got around to it unfortunately!

Sorry that was in fact a Mikuni...