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Discussion Starter #1
I have honda cm 400 t and was wondering if there were a different carb options to run pods other than the stock CV 22 A...are there carbs that I could buy do I didn't have to reset and alter stock carbs
 

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see if you can find some Keihin CR22 smoothbore carbs.
 

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Yes there are several options. Most that improve performance will also increase fuel consumption. Pods directly connected to a carburetor never was a great performance design, too much wind turbulence around them is the simplest way to explain it. Carburetors work best when they can draw from a large volume of reasonably still air and where the air travels in nice straight paths into and through the carburetor, fuel can't atomize as efficiently otherwise.

There is a hint right there 'smoothbore' carburetor, why is a smoothbore in a carburetor a good thing; for precisely what I was trying to say above, less swirly wind turbulence and no even negative air pressure around the carburetor intake is way better then what pods directly on the carburetor give you. That is basically an open carburetor with the addition of some air filtration. Ever heard of a velocity stack? It's a real thing, a good air intake has one.

Some carburetors you see when you are shopping are better suited to 2-stroke motors, try to stick with ones that are typically installed on 4-stroke bikes. :cool:
 

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Go with vm30 mikuni's put a pair of 33's on a LTD 440 Bobber, It's a little ripper. I see them as low as 30 bucks new. have fun bolting them on because that's when the fun stops and the tuning begins. If you have never tuned a carb, just remember dual are twice the fun. CaTac recommended a great carb but I think putting Keihin's on a cm400 is a waist, you could buy another 400 lol
 

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Discussion Starter #5
Will check, thanks and stay safe
Go with vm30 mikuni's put a pair of 33's on a LTD 440 Bobber, It's a little ripper. I see them as low as 30 bucks new. have fun bolting them on because that's when the fun stops and the tuning begins. If you have never tuned a carb, just remember dual are twice the fun. CaTac recommended a great carb but I think putting Keihin's on a cm400 is a waist, you could buy another 400 lol
Tks man, life is definitely a learning curve as are old bikes...last one I totally went and just sold..
103617
 

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Discussion Starter #6
Will check, thanks and stay safe

Tks man, life is definitely a learning curve as are old bikes...last one I totally went and just sold.. View attachment 103617
I do have the carbs that came with bike and they are in pretty good shape..would it be easier to modify those and dial them in. If I get the mikuni , they have individual throttle so is that 2 in one ....and individual chokes on each carb..dial them in, not sure what that intails
 

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The CV carbs use engine vacuum to operate slides in addition to a butterfly valve that you operate by cable, (it's a pollution control / fuel saving device to make the motor run as lean as possible and represents the epitome of carburetor complexity which has thankfully been obsoleted by fuel injection)
the VM Mikuni type carbs on the other hand are strictly cable actuated, there is only 3 fuel circuits; low speed needle is a simple air screw, higher speed is controlled by a round slide that can have several different opening shapes, that in turn draws a long tapered needle that has 5 adjusting slots on it, the taper on the needle is adjustable by replacement. Choke is usually a fuel enrichment circuit that bypasses the slide throttle and dumps raw fuel into the intake port.
Fuel level to feed the main jet is controlled by a conventional float needle and seat.
The beauty of it is in its simplicity really, you can emergency clean and service them in the woods, with not much more then a swiss army knife and a thorn bush or cactus.
 

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Discussion Starter #8
Sounds ds like this is the way to go, would I use honda manifold boots or would I get them with the vm mikuni carbs..thanks for taking time to explain that for me
 

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Sounds ds like this is the way to go, would I use honda manifold boots or would I get them with the vm mikuni carbs..thanks for taking time to explain that for me
If you are buying the right carburetor it should fit the stock intake manifold adapter,
you don't get any extra mounting hardware when you buy carbs. You will likely have to devise a new throttle cable for it too, the one you have now likely has one cable to open and another to make sure it closes, the VM throttle will just be a straight pull cable connected to the slide inside the carburetor and the spring will be the only way to close it.
 

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Am I to use 2 carbs..i know this is a dumb question.....tks
Not really a dumb question, one carb for 2 cylinders is an option, it's just not considered a performance option. One big carb would necessitate a unique 1 into 2 intake manifold. One carb simplifies tuning because there is nothing to balance, it might even be a little cheaper but it is certainly not a popular aftermarket modification.
 

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Here are your carb intake boots for vm30 to honda 400e and mikuni make the single to double pull cable for their carbs. ://www.speedmotoco.com/vm30-intake-rubber-flange-adapter-cm400-cm450-p/009-00-1.htm . You lose top end with a single carb but improve low end, Not a good trade off
 

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Here are your carb intake boots for vm30 to honda 400e and mikuni make the single to double pull cable for their carbs. ://www.speedmotoco.com/vm30-intake-rubber-flange-adapter-cm400-cm450-p/009-00-1.htm . You lose top end with a single carb but improve low end, Not a good trade off
;) might be great if he was building a trials bike.


... just kidding, that would make a **** trials bike
 

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Not sure I understand the humor...is that not a good set up..
A single carburetor feeding 2 cylinders has a simplicity advantage and thereby a slight reliability advantage, but a dedicated carburetor for each cylinder is considered to yield a very slight performance advantage.

In very general terms, what makes for a good carburetor setup on a race bike is not the same as what makes for a good carburetor setup on a trials or street bike, they operate in a completely different environment :/ they don't run at wide open throttle 90% of the time.
 

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Couple of points.
Honda deliberately made those carbs very difficult to modify, the '3 jet' models were EPA lean with weird transitions and work very badly without stock air box/filters
CV carbs allow people to ride bikes they really shouldn't be riding as they have very poor throttle control (the person not the carb) It doesn't matter where the throttle is opened the slide will only lift according to what the engine wants/needs
Don't trust anyone who says they have carbs corrctly set up for your bike unless they offer money back guarantee you won't need to swap out slides, needles, emulsion tubes (jetting is OK to need changes)
SUDCO are pretty worthless as everything is 'proprietory' and they just sell a 'stock' VM30 (stock for a 1970's two stroke MX bike) Virtually nothing inside them will work properly on a 400 four-stroke twin
 
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Mikuni VM can be fitted with either a bleed type or a primary type main jet depending on your application.
Piston port 2-stroke uses a primary jet, but for a 4-cycle or 2-stroke rotary valve application you install a bleed type jet instead.

If you took the Mikuni off an old 70's 2-stroker and put it on almost anything else, that part would need to be changed.



"CV carbs allow people to ride bikes they really shouldn't be riding as they have very poor throttle control (the person not the carb) It doesn't matter where the throttle is opened the slide will only lift according to what the engine wants/needs"
That is the basis for the fuel conservation and reduction of exhaust emissions, they took away the operators ability to ham-fist the throttle.
 

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I know. I haven't seen any of the VM range for sale with emulsion tubes though, they all come with primary bleed. The ones I fitted to my XS 650 had a pair of emulsion tubes I machined to get various things working right.Emulsion tube and primary choke also use different pitch main jets which arte not interchangeable (without a big screwdriver)
 

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You are correct. New VM carbs are all jetted IIRC with Primary types, so they should be swapped with 2 size larger Bleed (emulsion) type needle jets and the air jets have to be replaced with something much smaller - say .5mm to start with.
 

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Discussion Starter #20
I'm beginning to think I just need to keep stock carbs, buy a air box..have a battery box and used fuse panel with electronics attached..use wiring harness and redu the area he cut out...at least I got the time..not necessarily the knowledge
103671
 
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