650/X-2 carb question

[Joker]

what is a good carb to run on a 650sx stock.
then with an a/m pipe and ada head?

 

[Vumad]

I had a 44mm SBN mikuni. Worked good. I think a 42 or 44mm are common.

 

[Joker]

On that water locked engine I got, it has a kehnin (not sure on the spelling) and I think it is a 42 but I am not positive. If so will that be sufficient for a 650


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[Vumad]

I never ran the 42mm keihin, but one of my parts skis had one on it. I have been told it was fairly popular but not as good as the 44mm mikuni. I'd just use the one that you already own.

 

[Joker]

Or I have 2 38's laying around which combo


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[Vumad]

I haven't ran either, can only tell you what I have read. I have been lead to believe dual 38's will perform similar to a single 42/44 but are harder to tune. However, larger carbs burn more fuel. It's a trade off that has advantages either way. I'd personally go with whatever takes the least money and maintenance. No reason to sell either to get a 44SBN imo unless they suck. So Pick which ever setup is nicer and more ready to bolt on and bolt it on. My X2 (has my 650 44mm SBN) would probably perform better with dual 44s or a single 46, but I already own the single 44 and it works perfect, so that's my choice. If you have plenty of money to spend, you can buy a single 44sbn. But, if money were no object, you probably wouldn't be using the same methods I did to obtain your parts.

Check GroupK.com for more info on how to get the most out of a set up.

 

[Vumad]

It's our position that the carburetor that can provide the best fuel mixing, at all throttle positions, is the carb that will provide the best overall acceleration and throttle response. Dual 38 carbs are commonly used on modified race boats because they can offer better overall throttle response than a heavily modified 44 Mikuni carb. 38 duals offer better response because the smaller 38 carbs can mix the fuel with the incoming air much more efficiently at partial throttle openings, not because they have greater volume abilities.

The 42 Keihin carb, used on all Group K Hammer kits, offers better overall fuel mixing and throttle response than any large throat single carb we have tested. This 42mm carb bolts directly onto the stock '91-'93 650 intake manifold where it works in concert with the small intake runners of the Group K modified '91-'93 650 manifold to provide throttle response and acceleration that no 44 Mikuni and few dual carb setups will match. The single 42mm Keihin carb has no troublesome linkage, and it features easy "two screw" mixture tuning. Your stock '91-'93 intake manifold must be bored slightly to accommodate the larger 42mm carb throat diameter. (the early 28mm type manifold will not accommodate the 42mm carb)

In our tests, the popular K & N flame arrestor replacements performed well as long as they were perfectly dry. However when they became even a little wet, they offered very restricted air intake ability until they were removed and allowed to dry out. For our Hammer kits we recommend the stock Kawasaki '91-'93 flame arrestor case and element. The intake mesh of the stock arrestor is so well guarded in the engine compartment that it is exposed to very little water spray. Whatever spray it may be exposed to will not clog the all stainless steel screen element in any way. The opening on the stock flame arrestor also matches perfectly to the throat opening of the new 42 Kiehin carb.

We have tested several dual carb kits on the 650 engines. Surprisingly they offered only slight increases in overall performance (about 1 mph). All the duals we tested proved to be very difficult to tune and synchronize. That, along with the high price tag, make them a very poor value. Stock '89-'93 Kaw. reed petals have consistently outlasted and out performed all the aftermarket reeds we've tested.

From Group K

 

[Joker]

Dude vumad thanks a lot your pretty damn helpful I am sure I will have a lot more questions throughout my build. Thanks man


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[Vumad]

NP. Don't take anything I say for solid information however. Most of what I know is based on what I have read, been told or error and not so much trial.

 

[Joker]

Ya but it will save me time even if I make some errors. Your helping me by leading me in a good direction


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