lack of feul on holeshot

[surlyjoe]

1960 big twin 40hp.<br /><br />evrytime I slap the stick to WOT from idle to get outa the hole it gets almost to a plane and then dies out. if you come up a little slower, or have someone pump the primer bulb, it does fine.<br /><br />I am geussing the vaccum goes to low to make the pump work?<br /><br />I put a new kit on the fuel pump when I rebuilt the motor and all new hoses. is there anything else I can do?

 

[tashasdaddy]

Re: lack of feul on holeshot

did you clean the high speed jet in the carb, and run a small wire thru it. blow everyting out with air. maybe the float is to low. check hoses for air leak.

 

[Paul Moir]

Re: lack of feul on holeshot

The pump works off positive crankcase pulses. The diaphram is returned to the normal position after the pulse by the spring behind it. So vaccum should not affect it at all.<br />I'm inclined to agree with tashasdaddy, but you have the adjustable high speed mixture control right? What happens when you set it a little rich? <br />I don't think it's really very likely, but is it possible you swapped the big and little springs during the fuel pump rebuild? Is there any evidence of air showing up in the filter bowl? It might be worth temporarily running a bit of transparent fuel line from the pump to the carb so you can check for bubbles.

 

[surlyjoe]

Re: lack of feul on holeshot

carb was rebuilt with OMC kit,new float,otherwise iy runs great runs great, I dont think I swapped the springs...but, if the return one was weak would it cause this? the kit I got had no new springs.<br /><br />have run it richer, doesn't seem to matter<br /><br />tank and hoses are new.<br /><br />I can run all day no problems as long as I come out of the hole without slapping the stick, its only the sunned idle to WOT that seems to do it

 

[JB]

Re: lack of feul on holeshot

You can verify that it is fuel starvation by pumping the primer bulb as you accellerate. It should take off without hesitation.<br /><br />I agree with the air leak theory, but check fuel tank venting, too.

 

[surlyjoe]

Re: lack of feul on holeshot

Originally posted by JB:<br /> You can verify that it is fuel starvation by pumping the primer bulb as you accellerate. It should take off without hesitation.<br /><br />I agree with the air leak theory, but check fuel tank venting, too.

oh, it takes off fine if some one gives the bulb a couple pumps after I gun it, and then runs fine.<br /><br />I got a new gas tank, but I verified the vent works fine.

 

[tashasdaddy]

Re: lack of feul on holeshot

if the new tank is one of the aftermarket plastic, i've had trouble with them sucking air, at the fitting.

 

[Ranger01]

Re: lack of feul on holeshot

I have also had that problem like t-daddy, mine was sucking in air at the fitting, i chased it and replaced a bunch of stuff instead of going step by step, i ended up spending 5 bucks on a new fitting that corrected the problem. Live and learn. Then get loves, when you find out it was simple and you messed your pants. Good luck