Super Jet Help me choose new carbs on 701/760

[torquen]

I have a RN SJ with a 701/punched to 760. Girdled head, factory type 4 pipe, dual 44mm Black Jack carbs.

I am looking at changing up my carbs because the dual 44mm Blackjacks eat fuel like crazy. I can go through 5 gallons of gas in no time flat. Where we ride I need some more distance but I don't want to loose all my power.

Should I go with Dual 38mm SBN's or a Single 44 SBN? Going to a single carb might get expensive because I have to buy an aftermarket intake manifold correct?

I still want to keep the low end and mid range hit that I have now. Don't really care if I loose a little off the top.

Let me know all your knowledge. Thanks,
G

 

[waxhead]

Dual stock 44 mikunis will work fine.

 

[torquen]

Would I gain much by going to Dual stock 44sbn carbs over the Black Jack 44's? Would the stock 44sbn carbs bolt up to my manifold?

 

[Matt_E]

You don't want to lose power, but you want to burn less gas.

 

[torquen]

I know I'm going to loose power by going to smaller carbs. But was hoping to keep the bottom and mid. Don't really care if the top end power drops. Just don't want it to fall on its face when I want a fist full of throttle.

My blackjacks now can burn through 5 gallons of fuel in under 30 mins of cruising around looking for boats.

I guess what I'm trying to find out is how much difference would I notice between Dual 38 and Dual 44's in stock form. Are Dual 38's just going to destroy my power? If I end up going to stock dual 44's will they suck quite a bit less fuel?

Can the stock 38's deliver enough volume to hold full power on my engine? Or will they fall off and cause the engine to go lean?
Thanks,
G

 

[Matt_E]

Something isn't right then.
I run twin 46 BlackJacks on a pretty modded out 763cc motor and 5 gallons will last me at the very least 1.5 hours.

 

[Powerhouse]

One of my friends has a 62t/61x top, with a single manifold hooked up to an OEM mikuni 46
It SIPS fuel, its crazy
We can get 4-5 days of riding on that ski, on a single tank (5 gal)

 

[NVJAY775]

Like Matt_E said. A buddy of mine has a 771 xscream with dual 46's and gets about the same run time.

 

[torquen]

I'm not sure why it uses so much fuel. The plugs are showing perfect burn. Does not feel or sound rich at all. The carbs never load up if I'm going through a 5mph zone. I could get more time out of the tank if I really babied the throttle but what fun would that be. I don't remember what jets I'm running but I did pull them at one point and talked to Jet works. They said I was running the correct size.

Would I be loosing a good amount of power by going to Dual stock 44's? Any would I gain much in fuel savings?

Most of my riding is chasing down boats to hit the wakes or doing some surf riding down in pismo.

 

[NVJAY775]

You could have art do you up some 38 blackjacks.

 

[Aircraftsalz]

Chris (Jetmaniac ) likes the stock 38's on his 701 to 781 motors... He always sell them with the stock 38's.... Motors rip off the bottom to mid so I would try 38's... Don't buy broke dick worn out ones, buy a decent or take off's.

I think Brian at Thrust has some brand new take offs for sale

 

[Berky]

X2 , I love the snappy throttle response with the 38s that Jetmaniac setup for me, he really has it dialed in now for the 710 to 780 motors he sells. I run 2.5 hours on a tank

 

[waxhead]

Your not necessarily going to lose power, Your engine is not making use of the fuel its getting.
38s will give you great throttle response off the bottom but they lack the torque of the 44,s in my experience

 

[Matt_E]

Your not necessarily going to lose power, Your engine is not making use of the fuel its getting.
38s will give you great throttle response off the bottom but they lack the torque of the 44,s in my experience

I think you're right, the 38's give way more linear response by mellowing out the bottom

 

[torquen]

What does that exactly mean? The 38's will tame down the "hit" on the bottom end?

I have been offered both 44mm stock SBN carbs and 38mm stock SBN carbs. The 38's come with the reeds, intake mani, carbs, and stock FA. I believe I have aftermarket reeds but cant remember. If I do have aftermarket reeds will they work with the stock intake and 38's?

Out of these two options what would be the best to choose from?

 

[waxhead]

Stock 44,s would be better
But you will need a 760 manifold and plate or an aftermarket manifold.
but the manifold the black jacks are on will work just fine

 

[Matt_E]

What does that exactly mean? The 38's will tame down the "hit" on the bottom end?

It means you will lose bottom end power.

 

[Freakrider]

From what I have read, 38's will have higher air velocity and have a snappy bottom end however they will produce slightly less horsepower than 44's because there is less supply of air/fuel as the engine produces rpm...Some engine builders say the same about a big single carb set up, less horsepower but great off throttle response due to air velocity.

 

[mademan9]

I say dual 38's. I have them on my jetmaniac motor and the bottom end hits really hard plus fuel last over 1-1/2hours of riding

 

[Mark44]

X2 for 38's.

Mark44