2-to-1 carb

So this thread is in the tech section however from the looks of it nobody ever got the 2-1 conversion dialed in.

I know someone out there has done this with success...
 
I ran a 142 main jet with everything else stock on my stock bs34 carb. Never could find a way to keep the left cylinder from leaning out, because of the 180 degree crank.
 
Interesting Thread

DCopp, I would like to see a little more info on what you did on your 2to1 manifold. Looks like you made it out of aluminum. Were those pre-made flanges you used? and what diameter is that??

Anyone else have any success? maybe w/stock carb?


I built this manifold and many like it for both XS400 and 650.
I CNC machine flanges and the rest is of course aluminum tubing.
All welds are finish ground smooth inside manifold for airflow.

Recommend silicone hose for the carb connection, can be found at most turbo suppliers.
Hose should be as short as possible. The hose is not a flow surface, just a sealing device for the carb/manifold connection. Carb and manifold should almost be touching when clamped in place.

As far as diameter...lol... measuring tools are your friend, I do this for a living and not interested in giving my work away free (that includes design time). Don't mean to be a dick, but it's like I wrote a "how to" book and you'd rather I told you "how to" for free instead of buying my book.
Wanna buy a manifold?
I'm building one today to ship to Australia!
Parts are on the shelf and each manifold is hand made in my fixture.



As far as if it works, on a 180* crank motor, one cylinder will always be lean, can't fix that completely. Better to jet so the fat cylinder is a little rich and the lean hole is closer to normal, than to lean out and burn a piston.

I am working on a new design that may help with the lean condition, but won't completely eliminate it. I'll post a thread when I get one finished.
 
I built this manifold and many like it for both XS400 and 650.
I CNC machine flanges and the rest is of course aluminum tubing.
All welds are finish ground smooth inside manifold for airflow.

Recommend silicone hose for the carb connection, can be found at most turbo suppliers.
Hose should be as short as possible. The hose is not a flow surface, just a sealing device for the carb/manifold connection. Carb and manifold should almost be touching when clamped in place.

As far as diameter...lol... measuring tools are your friend, I do this for a living and not interested in giving my work away free (that includes design time). Don't mean to be a dick, but it's like I wrote a "how to" book and you'd rather I told you "how to" for free instead of buying my book.
Wanna buy a manifold?
I'm building one today to ship to Australia!
Parts are on the shelf and each manifold is hand made in my fixture.



As far as if it works, on a 180* crank motor, one cylinder will always be lean, can't fix that completely. Better to jet so the fat cylinder is a little rich and the lean hole is closer to normal, than to lean out and burn a piston.

I am working on a new design that may help with the lean condition, but won't completely eliminate it. I'll post a thread when I get one finished.


well said, its not expensive to get sprocket to make you one. his price is very reasonable, for me the only expensive part was shipping, but thats what you get for living in Australia. it still worked out cheaper than getting someone here to make one:thumbsup:
 
A single carb set-up is one of the most popular modifications to do to the KZ400 and KZ440. Engine size affects nothing at all as long as the carb flow matches the engine's needs. It works fine (I did the single carb mod on my first 440, and plan on doing the same on the 400 I just picked up), and usually works better than the stock set-up. Tuning issues that our XS's have get cut in half with a single carb. No leaky carb boots, no need to sync your duals carbs, etc. I noticed no change in power whatsoever.


what kind of carb and jetting did you use, I was planning on doing this to my 1980
kz440 and just wasn't sure what carb and jetting I should use
 
Cool, a 2 into 1 carb thread. I'm in the middle of doing this myself having been inspired by the guys on the Kawi forums who all seem pretty keen on the idea. I'm not after any performance changes, just doing it for fun really, lol. Picked up a 34mm Keihin PWK for when I get the manifold sorted.

DSC02391.JPG


A lot of the Kawi guys in the USA seem to make the manifolds out of large diameter copper pipe from plumbing suppliers and braze the joints, which is a pretty cool idea.

There is also a bloke on the TCU forum called Choppersprocket who makes them I think for the XS400. I also found sombody here in the UK who makes a cast 2-1 manifold for the XS650 and asked him if he would consider making one for the 400 but he said no :shrug:

I was thinking of trying to make it out of steel exhaust bends done with a mandrell but I'm still having a bit of a think about it :)

Sorry HT you answered the question already...

try 11th hour industries that's were I got my 2 into 1 manifold
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so im doing the coversion to my 80 440ltd running a 35mm keihin pwk and im wondering if anyone has used this carb and know what jets they used
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i know this is a old thread but i had a though about doing this and im in the midst of building my intake right now, i am using a carb from a xs750 set and stripped it down and building a single unit to mount up to my intake, carb is a Mikuni BS34 cv
 
there's a guy who did a singe carb conversion, he posted a video of him doing wheelies when he was done with it

ill see if I can find the thread back
 
very nice and i plan n having the intake done tomorrow and hopefully mounted up i have everything i need minus a hose to connect the carb to the body but thats easy to get a hold of
 
so i have decied to do the 2-1 intake but cant find a intake pipe and locally cant find any one to weld aluminum so im making it out of cast iron pipe fittings as a preliminary till i find a 2-1 mani i plan on ding something along the lines of this, whats your thoughts
 

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The biggest issue with a 2-1 carb is the left side running very lean due to the 180* crank. The bike will run and go but it will have idle issues and over time the left cylinder will wear/ overheat. The guy that did this was only on here for a few days and then gone:confused: So there is no long term riding info to be had:wink2:
 
I always wonder why people think 1 carb is going to be better than 2. I am certain that Yamaha would have saved the money on our bikes and only used 1 carb if they could have. But they didn't, they installed 2 expensive carbs on our budget bikes and made less profit on each bike sold. Has physics or engine theory changed since 1980? No. Do any modern parallel twin bikes have a single carb or throttle body? Nope. Makes one think, doesn't it? Will 1 carb work well on our bikes? No.

If that isn't enough to convince you that you are headed in the wrong direction, I'm fairly certain that a handful of cast iron plumbing fittings will weigh more than the 2 carbs did. And that weight will be hard on your intake boots, especially when you hang a carb on the end of it all.
 
ok i understand the weight thing but those fittings were just a referance i dont plan on actually using cast iron fittings lol i plan on using mandrel bent piping for it nothing as heavy as plumbign fittings, but if done right you can make anything run correct lol just like my buddys gl1000 i remade the inake for him and instead of 4 carbs we used a weber carb setup ontop of a plenum connecting all the pipe and it ran amazing
and since the other guy left i willl do a riding test of it for you guys and let you know how it goes
 
just finished single carb ,used one carb from 2.6 liter yamaha outboard,homemade intake.also did top end and rings. new carb was mindless to tune,instant throttle response and have not touched carb since installed. spark plugs look great,have not changed any jet sizes on outboard carb just cleaned and installed.easy!!!!!!!!!!!!!!
 
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