Having carb problems

[rkm]

Fx-1 with 61x/61x. Stock carb modified by Novi.

The main problem is with the starting. It will start and die off the primer fuel a bunch of times before it will run on its own. Its really annoying. The motors almost warm before it will pull fuel.

And the second problem, which must be related, is on really long wide open runs it will run out of fuel.

I rebuilt the carb, hoping the fuel pump was bad. Same thing happens.

Any ideas?

 

[rkm]

The return hasnt been drilled. No need for a restrictor.
Jetting is 120/145. 2.0N/S 95 gram spring.

Im down to two ideas now.
Im not sure if theres a check valve in the tank vent. Does the return line pressurize the tank and need the check valve to build pressure?

Other is a larger needle and seat and keep the popoff the same.

Anyone care to give an opinion?

 

[tipafew]

I would check your tank vent.
I am assuming when you rebuilt the carb you replaced/cleaned the fuel screen in the carb.

 

[rkm]

Tank vent works, but doesnt take much to over power it(2 or 3 psi)
Is that right?

 

[rkm]

thanks for the help people

 

[tor*p*do]

Tank vent works, but doesnt take much to over power it(2 or 3 psi)
Is that right?

replace it; they are cheap
if that doesnt help strip down the carb and make sure you replace the check valves in the fuel pump

 

[ger87410]

replace it; they are cheap
if that doesnt help strip down the carb and make sure you replace the check valves in the fuel pump

kinda x2. I wouldn't go as far as replacing before rebuilding.

Sound like a fuel pump problem to me. Check that line (Why can't I think of what it's called??) from the carb to the engine for leaks.

 

[rkm]

Check valve replaced(OEM).
All fuel lines replaced and clamped.
Carb was rebuilt.

Now im thinking its sucking air from my primer. Opinions on that?

 

[ger87410]

That's never happened to me. I've primers on all 3 of my skis.

Pull the fuel line from the tank and check how much vaccuum is created by the carb. That should tell you if the pump is working right.

 

[rkm]

How much vacumn will there be?

 

[brett]

primer pump/lines(get hard and crack) are a pita. ditch it and manually prime if the ski...could definitely be your problem

i havnt ran a choke or primer for years

 

[rkm]

Still happening.

 

[ger87410]

Did you feel any vacuum when you pulled the line?

It should be easily felt when you cover the hole with your thumb.

 

[rkm]

How much should there be? It doesnt change with other carbs. Its gotta be another bad check valve or pulse line. It doesnt build any pressure when my other skis do. Or a hole in a fuel line or something. Aggravating.

 

[ger87410]

What do you mean by asking how much there should be? It's irrelevant how much psi you should be looking for unless you're hooking up a vacuum meter.
There just should be a fair amount of suction. If you can't feel it, your diaphragm is suspect.

Beyond that, I can't tell you how much suction there should be. I'd be surprised if anyone actually did hook a meter up to measure.

 

[crammit442]

If the carb is Novi modified it likely has the return restriction drilled. If so, you will need to run a restrictor in the return line. A 60 main jet is a safe starting point.

 

[cmeripper26]

I had my stock Mikuni dual 38's modified by Novi to the 42's and i run into the same problem all the time with these carbs, my 2.0 needle and seats get hung up, the veins on the needle valve have scores up and down them. I have to keep replacing them, it's a stupid ass problem. I just saw that you had carbs modified by Novi so i thought i would chime in!

 

[rkm]

Found the problem. The fuel selector had a crack. With a bad check valve, it sucked air. Finally getting a good one in there, it sprayed fuel at WOT. Oh that and theres something in my ON line in the tank. It seems to plug up at anything more than idle.