Spitting Carb

[GaryZ]

My #1 carb is spitting enough fuel to make the air box wet.

I removed the air cleaner to verify which carb.

It does not seem to spit at idle, only above.

 

Ideas and comments are welcome . . .

[Kirby]

Intake valve not closing? No clearance on valve?

[frankd]

Or a broken valve spring or a bent valve.

[lvsloan1]

My 1990 Venture stays wet under the air cleaner but it's by all carbs, not just one. I have never paid attention to it cause the engine runs great so I didn't think it was a problem. Guess I need to take a rag and dry it to see if it gets wet again and which area gets wet first. Thanks for this post!

[Peder_y2k]

A spitting carb can be the result of a poor performing carb function. This results in an improper fuel mix that causes a reverse pressure condition. Most probable is fuel level being low, or a blockage of the low speed system including pilot that creates a 'lean' mix. Sometimes a leaking fuel inlet valve can create flooding resulting in a 'rich' condition with same spitting result.

Other causes are malfunctioning spark plug/s, spark wiring, and ign. coil, but the coil is unlikely a problem.

Mechanical issues such as sticking, burned, or leaking cylinder valve/s, but the spitting would occur every piston stroke, and be quite regular.

These stated service areas are indeed a PIA to process through.

Start by synching the carbs, and clean/new spark plugs, checking plug wires and connecter cap/s, then move to the carbs confirming internal fuel level. From there, try adjusting the pilot screws.

Following that, an engine compression test is in order to isolate mechanical issues.

There's your start........Good luck........

-Pete, in Tacoma Wa USA

[Patch]

Thinking if this is just a sudden event, I would compression test 1st, warm engine 5 rotations if that shows well or at least even Peder schedule is the way to go.

S/G

[GaryZ]

A spitting carb can be the result of a poor performing carb function. This results in an improper fuel mix that causes a reverse pressure condition. Most probable is fuel level being low, or a blockage of the low speed system including pilot that creates a 'lean' mix. Sometimes a leaking fuel inlet valve can create flooding resulting in a 'rich' condition with same spitting result.

Other causes are malfunctioning spark plug/s, spark wiring, and ign. coil, but the coil is unlikely a problem.

Mechanical issues such as sticking, burned, or leaking cylinder valve/s, but the spitting would occur every piston stroke, and be quite regular.

These stated service areas are indeed a PIA to process through.

Start by synching the carbs, and clean/new spark plugs, checking plug wires and connecter cap/s, then move to the carbs confirming internal fuel level. From there, try adjusting the pilot screws.

Following that, an engine compression test is in order to isolate mechanical issues.

There's your start........Good luck........

-Pete, in Tacoma Wa USA

 

 

Really good stuff . . . Thanks!

I usually think the worst (valves? oh no!) and I will definitely do a compression and leak-down test. The carbs have been a continuous headache on this 1985 machine, and I was hoping someone else would agree that the carbs could be at-fault again . . .

[Yammer Dan]

Sea- Foam Time.

[GaryZ]

Update:

Checked compression and leak-down (sort-of). All good

The problem must be carbs again