Bucking Cruiser (1 Viewer)

[MtnTrucker]

Do you know anyone with a carb like yours and the vehicle runs fine? If so, see if you can swap their carb on for a quick test. If it runs good, put yours back on and see if the problem comes back. If it does, ship it to JimC and have him do a performance rebuild on it.

 

[FJ40Jim]

Ignore the second barrel.

It is a one barrel w/ a pilot jet and a main jet. Simple.

Sounds like the idle circuit could be too lean. It is not a jet that is too small, the stock slow jet is adequate. There is an obstruction to fuel flow, or a vacuum/air leak.

 

[cagiva900]

First off, thanks to everyone who chimed in to help, especailly FJ40Jim. I feel like I'm getting closer, but still not there. So here's a few more questions:

Is there only one port (ie main jet) to the emulsion tube or multiple ways fuel can get into the emulsion tube and out the top of the carb. The reason I ask, is under light throttle it seems to have a hard time getting fuel out the emulsion tube to spray down the carb. But on heavier throttle plenty of fuel slows out the main barrel.
With a vacuum/air leak wouldn't that affect the idle and entire RPM range?? I've looked and sprayed starter fluid around the carb, vacuum hoses, carb base, intake manifold, but everything seems fine, not to say I haven't missed something yet.

Anyways I can't understand why it's struggling to get fuel off idle and first 1/4 throttle but idle and everywhere else it runs great. Also when I put peddle to the floor the secondary (second barrel) works great too.
If the emulsion tube was obstructed it should limit the fuel not just at 1/4 throttle????

John

 

[FJ40Jim]

All fuel to the emulsion tube has to pass through the main jet. The only way around the main jet is through the power valve, but that is not causing this symptom, because it is not a problem under heavy load.

When a carb runs like you're describing it is because fuel is limited at the top of the slow ('pilot' in MC terms) circuit. Or it could be that flow out the main is starting too late, possibly due to a problem w/ the air emulsion jet or emulsion tube.

The primary and sec. booster have different size emulsion jets. Maybe they are swapped.

Something else that could lean out the carb is a problem w/ the HAC or missing HAC o-ring(s) inside the carb.

 

[piecemeal]

How do you have your fuel filter mounted? In a horizontal or vertical position? I had mine in a vertical position and was getting the same problems you are describing, then remounted it in a horizontal position and now, no problems. Air lock in fuel pump??

 

[cagiva900]

Still struggling.

Well Ive spent alot of time on the carb. Soaked it over night and cleaned it very well. Blew threw every port and orifice. The carb is clean.... put all new seals and gaskets and put it back together and same problem. One thing I did notice is in neutral the car won't hold at a steady rpm at 1600 to 1800. It revs up to it then surges back to 1000 then back to 1600 over and over. If I go over 1800 rpm it will stabilize.

Any more suggestions???