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Old May 2nd, 2017, 02:35 PM   #1
Wanderer
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Has anyone ever heard of a single carb setup for a Ninja?

I have a 2-to-1 carburetor mod for my Virago XV750.

I was wondering if anyone has tried making one for a little Ninja 250?

Advantages:

- No carb syncing required.
- Fewer parts to buy, maintain, fix, replace
- Takes less room on the bike
- Easier to remove
- Easier to troubleshoot, tune, change jets
- Cheaper to maintain(less parts)

Just curious.

Last futzed with by Wanderer; May 3rd, 2017 at 12:11 PM.
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Old May 2nd, 2017, 02:41 PM   #2
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Very interesting idea. I'm very curious as well to find out if it's been done before.
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Old May 2nd, 2017, 02:49 PM   #3
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Quote:
Originally Posted by Snake View Post
Very interesting idea. I'm very curious as well to find out if it's been done before.
My XV750 is a V-twin with the 2 carbs originally stuck between the two cylinders(one facing toward the front cylinder and one facing to the rear cylinder). The carbs are actually a bigger pain-in-the-a$$ to get out and to tune than the Ninja carbs are and that's saying something.

The dual carb to single mods use a steel manifold and move the single carb near your right knee, out from between the cylinders. Very nice setup.

Easy to get to, better air flow to the cylinders, easy to jet, easy to troubleshoot. I use one of the two original Yamaha Mikuni carbs as a single. Needs larger jetting, but works great!

Harley-Davidson has been using 1 carb for over 100 years...
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Old May 2nd, 2017, 03:05 PM   #4
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Here is a DIY steel manifold that I bought for my Virago XV750.

As I mentioned earlier, the 2 carbs originally faced 180deg (opposing) each other. One connected directly to each cylinder.

Now, I use this steel manifold to place the single carb to the right side of the bike, near my right knee. Works very well using one of the two original Mikuni carburetors that came with the bike.

Note: Unlike the V-Twin Harley's, the Yamaha Virago V-Twin cylinders are offset. Front cylinder is offset to the right and rear cylinder is offset to the left side of the bike. That is why the dual-to-single manifold mod looks like it does with one tube longer than the other.

The very bottom manifold flange, in the picture below, connects to the single carburetor through a rubber carb boot. The left and right flanges connect to front and rear cylinder.
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Old May 2nd, 2017, 03:15 PM   #5
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This one is for an old VW intake, but a Ninja dual-to-single carburetor setup would look something like this, only a little shorter.

It could be welded steel instead of cast aluminium. Some people have even used PVC plastic tubing or copper tubing soldered together to try and make their own. I decide to buy one made of steel and fabricated by a guy on Ebay.
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Old May 2nd, 2017, 03:26 PM   #6
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In case you are curious, the metal intake manifold flange can fit to the carburetor with a boot similar to the one below(You would only need one of course.). This rubber/metal boot bolts to the flat metal manifold flange and the carburetor clamps on to the rubber boot with a hose clamp, much like the way the Ninja carbs mount presently.

The boot has a vacuum port for your vacuum petcock or other vacuum lines.
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Old May 2nd, 2017, 04:13 PM   #7
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Single Carb Manifold mounted on a Virago.

I would think that a Ninja dual-to-single carb manifold should be even easier(in-line twin cylinders).

Maybe someday I'll try it once I get my 2 bikes(2007 Ninja 250 and 1991 Yamaha Virago XV750) working right.
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Old May 3rd, 2017, 12:57 AM   #8
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A old webber would look sweet, but then I'm old,.................and stupid........
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Old May 3rd, 2017, 05:16 AM   #9
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similar to this?
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Old May 3rd, 2017, 11:57 AM   #10
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Quote:
Originally Posted by mediace View Post
similar to this?
Exactly! What is this from? Is it made for the 1997-2007 Ninja 250?

The question is the distance between the 2 intakes and their port diameter. This seems pretty close though.
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Old May 3rd, 2017, 12:09 PM   #11
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Quote:
Originally Posted by MLR View Post
A old webber would look sweet, but then I'm old,.................and stupid........
I would start with one of the existing Ninjette carburetors with larger jetting.
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Old May 3rd, 2017, 02:05 PM   #12
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If I owned one of those in-line 4 cylinder Japanese bikes with 4 carbs, I would certainly be looking into a 4-carb-to-1 mod! I would go mad trying to tune, jet, balance, sync 4 carbs!!!

I would have fabricated for me a 4-to-1 steel manifold with one large carb sticking out the right side or the left side of the bike, Harley style.

I wonder why this is never tried? At least I have never seen it.
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Old May 3rd, 2017, 02:24 PM   #13
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Quote:
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I wonder why this is never tried? At least I have never seen it.
Performance.
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Old May 3rd, 2017, 02:43 PM   #14
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So I guess you must all be youngsters. Back in the 70's when most bikes were twins & if 4-stroke they usually only had 2 valves per cylinder. The performance models would have a carb per cylinder & the commuter/cruiser/shopping bikes would have one carb. But all basically had the same engine with maybe different cams.

A single carb model robs you of the intake pulse tuning, so fine for low to midrange power, but NOT good for maximum performance. A single carb made the bikes cheaper too, so that is why it went on the plain old cooking models. A single carb model would lose 25-40% of its peak power output, but would give better mpg, if not thrashed everywhere.

Your choice
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Old May 3rd, 2017, 02:46 PM   #15
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Quote:
Originally Posted by Triple Jim View Post
Performance.
Jim, I did a lot of research for my Yamaha Virago when I was deciding to go to a single carb myself. Hundreds have done this mod. It just isn't true that having a single carburetor hurts performance. It DOES change the power band though. With a single carburetor you get more low end torque, a wider power band and smoother performance and stronger pull. This has to do with smoother manifold pressure.

If you need higher revs and quick response, then multiple carbs may help that, but if you need great low end torque, a smooth power band and easier tuning, then a single carb can give you that.

Ask yourself why most performance cars today have gone back to a single carb? Yes, gas mileage, but also smaller size engines need a wide power band and not just quicker response. Ask Harley-Davidson.

Just my take on what I have read. If you want to hear what Virago owners have said about this mod, go to YouTube and Search on: "Virago Single Carb"

Peace
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Old May 3rd, 2017, 02:54 PM   #16
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Quote:
Originally Posted by Mohawk View Post
So I guess you must all be youngsters. Back in the 70's when most bikes were twins & if 4-stroke they usually only had 2 valves per cylinder. The performance models would have a carb per cylinder & the commuter/cruiser/shopping bikes would have one carb. But all basically had the same engine with maybe different cams.

A single carb model robs you of the intake pulse tuning, so fine for low to midrange power, but NOT good for maximum performance. A single carb made the bikes cheaper too, so that is why it went on the plain old cooking models. A single carb model would lose 25-40% of its peak power output, but would give better mpg, if not thrashed everywhere.

Your choice
No, I'm in my 60s. Listen, performance isn't everything. Most people are so bad at multiple carb tuning, balancing and synchronization, they lose any performance gains that multiple carbs may offer.

But, I agree. For high revs, quick performance, like on a race track, yes, multiple carbs are the answer. But, most people, especially with smaller engines could benefit from a wider performance band and more low end torque.

One last point on "intake pulse tuning". In my old and feeble mind, good engine power is all about a sooth and constant intake manifold pressure, which a single carburetor gives you. Most people aren't racers or even mechanics, they are just riders that want a good running, reliable and easy to fix engine. Motorcycle manufacturers use multiple carbs because it is a sales gimmick. They want people to think they have a racing bike. Most people can't maintain a commuter bike, much less a complicated racing bike.

As I have said around here in almost every thread I post on, SIMPLICITY IS ALWAYS BETTER. I believe that the easier we make things, the better life gets. Thus, my view on bike carburetors.

Just my opinion.
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Old May 3rd, 2017, 03:00 PM   #17
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Originally Posted by Wanderer View Post
Jim, I did a lot of research for my Yamaha Virago when I was deciding to go to a single carb myself. Hundreds have done this mod. It just isn't true that having a single carburetor hurts performance.
I should have said "peak performance".
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Old May 3rd, 2017, 03:10 PM   #18
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Quote:
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I should have said "peak performance".
And I agree! But, do most riders really need "peak performance"? Or do they need a wider power band, smooth throttle response and ease of maintenance? This is especially true on smaller size motorcycles.

Most people do not race their bikes and need instant peak performance. They need easy cruising, good low end torque and reliability.

Look at what young riders do with "peak performance". They quickly wreck their bikes and then patch them back together with tape. So much for peak tuning and perfomance.
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Old May 3rd, 2017, 03:42 PM   #19
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For sport bikes, peak power sells. For cruisers, all around rideability sells. But I would not say that the stock setup of a Ninja 250 is too peak power oriented. I think Kaw produced a good compromise of rideable torque and peak power.

It would be very interesting to see dyno curves of a stock 250 and a well designed single carb 250.
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Old May 3rd, 2017, 03:46 PM   #20
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To any posters and any of my friends around here.

I know that I must sound like a broken record when I post my views. In truth, I would not have the great bike that I do without the help of many around here.

I am NOT a bike racer, a mechanic or even a great rider. BUT, I have learned one very valuable lesson in my years on this planet. The easier, less complicated and simple I make my life, the easier life becomes!

I'm sure that you guys must get tired of hearing it, but it rules everything in my life today. I make sure that I follow this philosophy in all aspects of my daily routine.

If I can make my life less complicated, then I try to do that. If I see a way to simplify the way my motorcycle works, I get excited. If I see a way to make my little pickup less complicated, I do. I see all aspects of my life in this philosophy, including diet, finance, what I own, what I find exciting, how I travel, what my personal goals are.

So, try not to let my views irritate you. I am only concerned about what works for me. You are free to do the same. That is what life is all about, FREE WILL, in other words, CHOICE.

Peace and thanks for listening to an old man's ravings.
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Old May 3rd, 2017, 03:48 PM   #21
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Quote:
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For sport bikes, peak power sells. For cruisers, all around rideability sells. But I would not say that the stock setup of a Ninja 250 is too peak power oriented. I think Kaw produced a good compromise of rideable torque and peak power.

It would be very interesting to see dyno curves of a stock 250 and a well designed single carb 250.
I agree. I would like to see that also.
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Old May 4th, 2017, 12:07 PM   #22
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Quote:
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Ask yourself why most performance cars today have gone back to a single carb? Yes, gas mileage, but also smaller size engines need a wide power band and not just quicker response. Ask Harley-Davidson.
As you probably know, most new cars regardless of if they are a performance or daily drivers DO NOT use a single carb. They may utilize a single throttle body, but each cylinder gets its own fuel injector - sometimes even two injectors per cylinder. Syncing multiple carb setups really isnt difficult at all.

Also, it seems you are not really comparing apples to apples. By removing just one carb and using one OEM size carb to drive two cylinders the main factor in any low end ridability achieved is the decrease in orifice size and the resulting increase in flow velocity at low engine speeds - not the fact that youre reducing the number of carbs. You could achieve this same result with two carbs, decreasing the carb size. You could even achieve it with 3, 4, or even 10 tiny carbs sized correctly.

For the 250, to cut the flow area in half that would be about a 22mm carb set instead of 30mm.

More power to you though, I hope that you can do it. I would look at using around a 35mm carb if you can find one, it should give you a good compromise on low speed response while not sacrificing too much top end.

Not sure we should ask HD anything... Their newest 1200 makes about 60 ftlb/L (70.8ftlb total) torque while something like the Kawasaki Z900 makes almost 80 ftlb/L (73.1ftlb total).
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Old August 9th, 2022, 01:21 AM   #23
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I run a single carb on my 2000 250r, I built the manifold out of 1in pvc and run a single Keihin 30mm "pumper" carb..I crack off 13,500rpm upshifts all day long, I love my setup
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Old August 9th, 2022, 08:43 AM   #24
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Hi and welcome!

Were you having carb issues before?
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Old August 9th, 2022, 10:42 AM   #25
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Quote:
Originally Posted by Streetfightersteve View Post
I run a single carb on my 2000 250r, I built the manifold out of 1in pvc and run a single Keihin 30mm "pumper" carb..I crack off 13,500rpm upshifts all day long, I love my setup
I ran a similar setup years ago, it was fantastic. I would consider it again if I had the need. I love the PVC manifold, very clever!
Here was mine: https://www.ninjette.org/forums/showthread.php?t=267999
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Old August 10th, 2022, 12:02 PM   #26
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I run a single carb on my 2000 250r, I built the manifold out of 1in pvc and run a single Keihin 30mm "pumper" carb..I crack off 13,500rpm upshifts all day long, I love my setup
Nice setup! Do you have more info about your build? That is rather interesting.
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Old August 10th, 2022, 03:42 PM   #27
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Those setups are wild.
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Old August 10th, 2022, 10:36 PM   #28
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This is similar set-up to Honda Rebel 250!
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Old August 12th, 2022, 12:41 PM   #29
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A old webber would look sweet, but then I'm old,.................and stupid........
Well, apparently the Ferrari 250GTO was named after the displacement of one cylinder. We are running 125cc per, so something about half the CFMs of an IDA 48 couldn't be too far off... I doubt they made them that small though
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