Dual Carb....

Ok...1. Has anyone every heard of a dual carb XJ. Im tired of trying to find a carb rack, I would like to just use to carbs. What do I need to do...what size of carbs will I need....

 

Since none of us know what your bike is, the question is rather ambiguous. You can get away with any size carbs, but they'll need to be jetted (no different than adding pods or high flow exhaust), and the power band will probably move. Assuming that you have a 650 since most of us do, you can go with carbs from a 1000 cc bike and be pretty close. You'll want carb number 2 and 3 (the middle two). This will create unequal intake lengths though which may affect how the outside and insides holes work together. It is a novel project, but one that probably doesn't have a lot of pioneers.

 

I made a custom manifold late in the season last year for a friends XJ750 maxim and adapted a 2 barrel side draft harley type carb. Worked great but still needed some more jet work when it left the shop (I didn't have any jets for it otherwise it would have been done).

Bike revved much better then I remember my dads 750 did years ago (only comparison I have).

I think I have some pics I took somewhere. It did take me quite a bit of welding/fabrication on the intake but could possibly make another (maybe even get it cast so it can be reproduced easily).

Sean Morley

 

This is a Maxim 750. So you think that any carbs from 1000 CC bike will work....But nothing lower than that I take...

 

carbs from a smaller engine will run it, but they will lower the power curve and overall rpm range.

 

Well....I'll try to get something off of a 650-1000 CC range...if someone can help me build the "Y"adapter to them.

 

anymore input!?

 

I don't have any "input" 4 ya. But I am looking forward 2 this build... +1

 

They've been doing the 2-into-1 carb setup on 750 Hondas for years now.
Here's a link to one of the sites I found:

http://www.cyclexchange.net/Honda%20Page.htm

 

What size carb do you think I would have to use...if I wanted to use just one carb to power the engine...?

 

Oh boy, that's a good question. I'm no expert. I assume a carb from a small 4 cylinder car engine would be close to the correct size, but not sure about that either.
You would need to fabricate a manifold for the carb to fit on the bike with enough room for the carb to fit on and there isn't a whole lot of room right there! This could get interesting to see if anyone comes up with a solution.
I myelf would like to simplify the carb setup also, that's why I thought of using two carbs instead of four. I never gave the single carb much thought because of the complexity of the manifold fabrication.
I can't understand why my Honda Accord can run so good with a single carb and get excellent gas mileage. Now why can't the motorcycle manufacturers just use one carb? It would seem to be so much easier to make it so simple. There must be some performancce issues is all I can think of.

 

There's a company that does a conversion from a dual carb set up toa single carb on the V Star 1100.

Originally, his setup used one of the bike's original carbs (37mm), Now I think they are using a 40mm HSR Mikuni.

Pepole who've done the conversion said that the low end torque goes through the roof, but they lost some of the top end power.

Here's a link to the site. It may give you some ideas.

http://www.kjsmotorcycleworks.com/

 

Well there are also members on the board who are doing Fuel injection conversions, but they refuse to update us on their progress.

 

I can try to find pics of the 2 barrel side draft conversion we made. We remounted the battery and removed the stock airbox and used a custom filter (came with the carb).

Other then making the intake and support bracket the rest went on very easily.

Sean

 

Applied physics will tell you that the bike will run better on the Cubic Feet per Minute through 4 Carbs than the CFM of 2.

What you should do is Master the Hitachi Quad Rack.
Learn the Hitachi and Mikuni Tuning and put the Bike on the edge of Fine-tuning.

The Cleaning and Clean-tuning part is something that gets easier every time you go through the Carbs.
Do 'em right and protect the Fuel Inlet with an Inline Fuel Filter and you've got the Carbs Cleaned for one or two seasons.

On the top-end ...
Getting the Diaphragm Piston Bores de-oxidized and polished goes a long way toward getting the most out of the Rack.

Mixtures:
That which befuddles most Tuners ... setting the Pilot Mixtures right has been made easier with the advent of the Colortune Plug.
Now, you can set-up the Pilot Mixture Screws to be within a few degrees of Super Fine-tuning by using the visual cue of the Colortune Plug.

Ultra Fine Tuning:
You become an Ultra Fine-tuner when you can "Hear" and "Feel" that the tune needs a tweak and read theh Plugs to determine what hole(s) need the tweaking.

Hesitation and bogging-out should be a thing of the past with the information available in the many Threads we have generated concerning fine tuning.

Take the time and energy you would expend on trying to fabricate a Manifold that will make the bike run worse and spend that time reading a Mikuni Manual.
Much of what you would do to a rack of Mik's can be applied to the Hi-tots to make your bike a performance machine.

You only need to learn:
Cleaning
Polishing
Synchronizing
Mixture Adjustments

 

Did you find a picture of and can you send it to if so please

 

The thread's ten years old, and that person hasn't been on in nine. A search will get better results for you.