Carburetor conversion

Has anyone ever put just one carburetor on a 1981 maxim XJ 550? I have 4 and I'd like to make it a single carb if possible.

 

There was someone here who did 2.

Don't think anyone did a single carb.

 

A single carb brings with it several compromises, most of which will result in the bike being down on power.
Why is it that you want a single carb?

 

So that he doesn't have to synch them. Why else?

 

He could put a giant Holley on it and a pod the size of a pie plate.

 

Orange-n-black was the user who changed to less carbs. He nearly got it good, but had to abandon project due to health. Don't think he stops by too much anymore. Search threads by him, you'll find it. Pretty impressive prototypes!

 

a dual feed double pumper..............

 

Hmmmmmm. Sounds like the makings of a rocket sled!

 

I did it on a GS850 (on two of them). Takes a lot of farking about, tbh, and that was using a lot of prior knowledge.
However, it's do-able on just about any engine, if you accept the loss of top speed simply due to the insufficient gasflow of a simple manifold and single carb.
http://www.xjbikes.com/forums/threads/single-carb-mod.30257/page-6#post-472411
I was driven to it by the sheer obscene cost of rebuild parts 25 years ago, to rebuild not just one, but two banks of carbs. Much cheaper to nip down the breaker yard and source bits I knew about.

 

Nearly 5 years later has anyone come further with the push for a single carb?

 

Dave in Ireland is still here with us

you could do a search for Orange-n-black he has info posted

some of his info here
https://www.xjbikes.com/forums/threads/4-into-1-carb.118203/#post-592451

 

Mine is running better than ever, with changed needle and spring. The addition of an AFR gauge kicked it up a notch, as I could see exactly what was happening at different stages and avoid top end weakness.
Also now playing an important part is an MGB air intake smoothing entrance to get less turbulant flow into the venturi, and the fitment of a fairly decent sized K&N cone filter to make utterly sure there would never be an airflow impediment issue.
Frankly, it's now going like manure off a shovel and redlines easily in all gears. Of course, part of its accelerative eagerness is the lower gearing from the 15" wheel, but damn, it feels great.

 

I am currently looking at having to try and make up one good set of carbs for a XJ900f out of three sets of carbs that have been languishing in a cardboard box on a shelf 20 years or more. I have done similar carb refresh jobs in the past with success.
But a single carb is an inviting prospect, and i have an SU carb off i think a 3.5 litre rover v8.
Anyone care to hazard a guess , of how much BHP is likely to be lost with a single carb conversion, on a XJ 900 891cc which is around 100BHP if i remember correctly.

 

A single 13/4 us will be just right for 100bhp, provided you have a decent shape inlet manifold.
Therein lies the issue I believe - there isn't much room.

 

Could you have it going into a plenum chamber ? Could be made close in to head that way. My SU is that short downward facing inlet off the v engine.
Would be quick to rebuild and set up.

 

Things I found out.
A 1.75" SU isn't happy with the air pull of an 850/900 engine at idle. It stumbles and farts and is never idling properly.
A 1.5" SU is almost happy, once the temperature is up.
The CFM figure of a HIF38 is more than adequate for the power output of the lump, providing the manifold is at least a stage above a gas-pipe special.
Much fiddling of springs and needles ensues.
There are surprises along the way.