stock 38s fuel line setup

[michaelbrenner]

I am switching my '92 sn superjet to a 62t case 61x cylinder motor from a late model superjet. For economy, I sourced a set of used stock 38 mikunis from another board member. I have some fuel line routing questions.

My 62t upper case half is ported and has been tapped for an additional pulse fitting, so there are now two pulse fittings, one on each side of the case near the base of the reed mating flange.

I have stock dual 38 mikuni's now and was wondering if I should plumb them to have seperate pulse signals and how to plumb the rest of the fittings between fuel feed and return.

I'm already planning on filling the stock crossover on the intake manifold to increase signal. Would modifying this plumbing theoretically help my performance in terms of throttle response and tuning ease?

Could anyone post a pic or diagram of how to route these hoses? Thanks.

 

[JonnyB]

Yes each carb should have its own pulse fitting! Now for the fuel return I have the two carbs going into one line then to the tank. For the Fuel feed I have two lines from the tank one for each carb. This is up to you. One option is to do what I did BUT then you will no longer have the Reserve. Go to the Tech FAQ and find the thread that says BEFORE YOU REMOVE THAT SELECTOR and read up.

 

[Big Kahuna]

Yes each carb should have its own pulse fitting! Now for the fuel return I have the two carbs going into one line then to the tank. For the Fuel feed I have two lines from the tank one for each carb. This is up to you. One option is to do what I did BUT then you will no longer have the Reserve. Go to the Tech FAQ and find the thread that says BEFORE YOU REMOVE THAT SELECTOR and read up.

Incorrect, if they are OEM 38's the carbs only utilize one fuel pump. the other carb is slaved to the pumped carb. You would need to plug that extra pulse fitting.

 

[Bonzia Bob]

Yeah, what he said ^^^^

 

[michaelbrenner]

So is there a good picture or diagram of how to route these hoses and such. Right now I have a single 44 mikuni on my 650 so this is a bit different. Is it simpler than I'm thinking?

 

[Bonzia Bob]

Your fuel in will go into the main carb (the one with the pump) then the return line of the main carb goes into the slave carb, then to the return on the fuel tank. Only one pulse line is needed for the main carb.

 

[JonnyB]

Incorrect, if they are OEM 38's the carbs only utilize one fuel pump. the other carb is slaved to the pumped carb. You would need to plug that extra pulse fitting.

wow didn't know that. but why couldn't it be set up like the way I said or is it because of the 38s. Thats how I have my 44s set up but also they are on an R&D intake (I need to stick to my 66E motors)

 

[Big Kahuna]

wow didn't know that. but why couldn't it be set up like the way I said or is it because of the 38s. Thats how I have my 44s set up but also they are on an R&D intake (I need to stick to my 66E motors)

You could, but you would have to install a fuel pump on the slave carb to run dual pulse/pumps....... but honestly, the 38's can only pump some much fuel, and the pump on it does the job just fine, if you have more motor than those carbs can handle it is time to step up to 44's or 46's.

 

[JonnyB]

You could, but you would have to install a fuel pump on the slave carb to run dual pulse/pumps....... but honestly, the 38's can only pump some much fuel, and the pump on it does the job just fine, if you have more motor than those carbs can handle it is time to step up to 44's or 46's.

Gotcha I just pulled up the parts image I thought both carbs had pumps now it makes ALOT more sense.