serious fuel problem!

#1
I was breaking my new motor in with the bike up on a stand and everything was going fine ..... all of a sudden it bogs and dies. I see fuel dumping out of the air filter so i turn it off and cleaned up the spilt gas. Then i started it again without turning the fuel back on. Ran fine until the bowl was empty so i turned the fuel back on and it started dumping out of the carb again. I did install a pulse fuel pump from an old briggs motor. Is it to strong maybe? The motor was smaller than mine so I doubt it. Any ideas would be appreciated...
 

2SlickNick

Well-Known Member
#4
Yes the fuel pump is too strong and is forcing fuel passed the needle seat. You can ruin your needle and even get fuel dumped back into the crank case.
You need a return line. here is mine. As you can see The blue is at the bottom of tank and goes to fuel pump - the red goes to carb and then a tee - where the clear is the return line.
https://www.youtube.com/watch?v=qSeXAqt1Lz8

here is another vid but detailed.
https://www.youtube.com/watch?v=Jmja5aDE7DQ
 
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2SlickNick

Well-Known Member
#6
Only reason I did a " T" and not a "Y" because my thinking is still most of the fuel goes to carb and not return. I figured a "y" was 50/50 to each :shrugs:
I am sure either will work just fine.
Good luck and Remove spark plug and cycle the engine a few times to see if gas comes out. Also change your oil and smell it for gas just to be safe.
 
#7
OK, approach this one with a sense of humor.......BUT, as an alternative to adding a T in the line and running a line back to the tank, if i were to perforate the pulse-line a little bit, would it make the pulse weaker resulting in less fuel pressure at the carb? Is that ridiculous?
 
#8
Yes the fuel pump is too strong and is forcing fuel passed the needle seat. You can ruin your needle and even get fuel dumped back into the crank case.
You need a return line. here is mine. As you can see The blue is at the bottom of tank and goes to fuel pump - the red goes to carb and then a tee - where the clear is the return line.
https://www.youtube.com/watch?v=qSeXAqt1Lz8

here is another vid but detailed.
https://www.youtube.com/watch?v=Jmja5aDE7DQ
in the second vid that was posted can I do the same thing but using the fitting for a crank case vent? and when you vent the block do you just run it to a catch can? sorry to go off topic but this video made me think of it.
 

2SlickNick

Well-Known Member
#9
OK, approach this one with a sense of humor.......BUT, as an alternative to adding a T in the line and running a line back to the tank, if i were to perforate the pulse-line a little bit, would it make the pulse weaker resulting in less fuel pressure at the carb? Is that ridiculous?
The theory sounds nice, but I imagine you then introduce dirt and other contaminants into the fuel, carb and then cylinder.
I was told that the pulse coming from the stock valve cover breather was too weak for a fuel pump. I would try that 1st before perforating the line.

I just drilled a hole in the top of my fuel tank and jb welded a 1/4" brass hose barb very simple and effective.
 

2SlickNick

Well-Known Member
#10
What fitting for the crankcase vent? Governor arm hole? - then yes. Do you mean the stock valve cover breather? - I would think if you could others would have done it.

I heard occasionally you have to watch for oil going into pulse line if you use gov hole or make one in crank case - then maybe a breather filter between would help.

I am not an expert just going off of my experience and what I have learned through reading.
 

bikebudy

Banned - Must pay $500
#11
What fitting for the crankcase vent? Governor arm hole? - then yes. Do you mean the stock valve cover breather? - I would think if you could others would have done it.

They use the valve cover vent or crank case on riding lawn mowers and in the past, I have used the Valve cover vent on a 7hp Tec , to run the fuel pump with no issue.

From what the OP was saying, He has a dirty carb, bit of crap under the needle.
 

2SlickNick

Well-Known Member
#12
Dang it, next time I will try the breather hose on valve cover before I go tapping it again.

I blame the pump for his problem because when he shuts the fuel off he can still run the engine without any of the fuel misting out and empty the carb bowl.
 

bikebudy

Banned - Must pay $500
#13
Well, I never seen a return line on a float carb before, so that was kind of neat.

You can restrict your return flow with an adapter T fitting .

1/4 on each end but, 3/32 in the center and small line going back to the tank.
 

2SlickNick

Well-Known Member
#14
Lol I suppose you could restrict it. I have yet to encounter this problem as it gets enough fuel to keep the bowl full without forcing fuel in it. A pressure relief valve is to high tech for this home hobbyist so I took a buddy's advice and did a return line.
 
#16
I have heard you can reduce fuel pressure in line when a fuel pump is used by adding a ball-cock style fuel on/off valve and adjusting it down
 
#18
Thanks Dave!! I believe I got the idea from a post you made on this subject on an older thread!! I bought the fuel valve, just have to install it
 
#20
I have mine going into the valve cover. I've not had any problems. It works just fine. I just went and bought a barb at the hardware store, and I threaded it into the cover easily. I don't this setup on my Hemi. The valve cover is just a thin pressed piece of metal.
 
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