How to fuel a motorcycle engine

[Smcgillis10]

I put a Gravity fed motorcycle engine on a kart and am having trouble fueling. I have a 2-4 psi fuel pump pushing fuel to the carbs but it floods the carbs.

It's an older motorcycle engine. So could I replace the seats to maybe hold the pressure of the pump? Or what? I'm going to try putting a potentiometer to try lower the pump pressure. What do you guys think?

 

[Half-breeder]

What Ive seen for over powered pumps, is a 'return line' going back to the tank. A "T" attachment after the pump fuel outlet. One end to the carb... the other to the top of the tank.

In theory, the back pressure is releaved by forcing excess pressure back to the fuel tank, instead of ramming it into the carb. Supposedly, the needle can stop the flow enough to not floodout the bowl/carb.

 

[mckutzy]

What motorcycle/engine did you use, for starters?
2 or 4 stroke?
Why not a petcock to regulate the flow, less hassle than messing with the electrical?

 

[Smcgillis10]

It's a 1983 Suzuki gs750. Peacock won't work. Need to have a fuel pump since then engine used to be gravity fed and that's no longer an option.

I ordered a vacuum pulse pump. They used them on other bikes. Should work. They should operate under the circumstances I need. I'll let you guys know b

 

[soggycrashed]

It's a 1983 Suzuki gs750.

Oh Jesus.

 

[mckutzy]

And why wont a petcock work?

 

[Badot]

And why wont a petcock work?

Petcocks don't make gas flow uphill

If running a simple T doesn't work, you just need an itty bitty tank above the engine... pump feeds gas from main tank to tiny tank, tiny tank feeds to carbs, and tiny tank overflows back to main tank. Carbs shouldn't be able to tell the difference so long as you have proper venting.

 

[ML-TOYS]

But the petcock can be used to regulate the gas flow by just turning it slightly to the on position.

 

[Badot]

But the petcock can be used to regulate the gas flow by just turning it slightly to the on position.

That'd be fine if there was a constant flow demand, but otherwise it'll either be too restrictive when the demand is high, or let too much fuel in when the demand is low.

 

[mckutzy]

OP- We need some pics.

 

[justinlogue5_0]

The vacume pump should work fine. I have a 87 Honda fourtrax that ran an electrical fuel pump because the fuel tank is below/under the seat. It has to pump up to the carb. When the factory and exspensive electric pump went out I bought one of those low pressure electric fuel pumps and had nothing but problems. Got fed up and ripped it all off and went to the vacume pump. It has never ran as good as it does right now with the vacume pump.

 

[thebozz]

The vacume pump should work fine. I have a 87 Honda fourtrax that ran an electrical fuel pump because the fuel tank is below/under the seat. It has to pump up to the carb. When the factory and exspensive electric pump went out I bought one of those low pressure electric fuel pumps and had nothing but problems. Got fed up and ripped it all off and went to the vacume pump. It has never ran as good as it does right now with the vacume pump.

Quick question: I have an xj600 motorcycle engine and I'm putting it on a go kart. I also have ran into the issue of supplying fuel and I ended up buying a 1-3psi electrical fuel pump and I used that. This flooded my engine, so, I bought a fuel shut off valve and closed it until it barely let any fuel past. This still floods my engine. I have a vacuum fuel pump too but how do I hook it up when the engine is outside the vehicle?

 

[justinlogue5_0]

Quick question: I have an xj600 motorcycle engine and I'm putting it on a go kart. I also have ran into the issue of supplying fuel and I ended up buying a 1-3psi electrical fuel pump and I used that. This flooded my engine, so, I bought a fuel shut off valve and closed it until it barely let any fuel past. This still floods my engine. I have a vacuum fuel pump too but how do I hook it up when the engine is outside the vehicle?

I looked every where for a picture for ya but I can't find it anywhere. Basically there is a hose (crank case breather hose) that was right behind the jug that goes from the crank case up to the air box. Just cut that hose and put a T fitting in there. Make sure its a size reducer T so the you can have the breather hose stay the same and the hose going to the pump is the smaller one. It took me a few minutes to get everything primed but after that it worked like a charm. If I come across those pics(or take new ones) I will send it to you.

 

[justinlogue5_0]

Here ya go

 

[Smcgillis10]

You need to hook it up to a vacuum port on your carbs or need to make one.

 

[thebozz]

You need to hook it up to a vacuum port on your carbs or need to make one.

Thank you guys for your answer and sorry for the delayed response, family came to town for the holidays and I was a bit busy. I have a crankcase breather hose but it is quite big, maybe 3/4" in diameter. I do have hoses coming out of the first and second carb, right now I just put a bolt in the hoses and hose clamed them to cut them off.

The big hose on the right is the crankcrase breather hose

This is the breather hose a little bit closer, notice how large this is

These are the hoses on the #1 and #2 carb

the hoses are on the left two carburators

My question now is, will a vacuum fuel pump have enough power to get fuel to the engine if the tank is below the carbs? the xj600 (If I understand correctly) is more or less gravity fed with the aid of the vacuum fuel pump.