I think I posted this question before a few months ago, but my problem is getting worse and I wanted to see if anyone has any new ideas.

WHen the engine is cold on my 93, I get a periodic spitting noise that sounds like its coming from one of the carbs. Once the motor warms up its fine, or at least less frequent or severe. I changed the plugs but that didnt make any difference as I expected.

I have never messed with the carbs. Are there any vaccum lines? Could it be a vacuum problem?

Could a carb sync inbalance cause this?

 

Is it possible that you are missing a vacuum plug on one of your ports....or maybe you have a damaged one that is leaking?

What exactly do you mean by "spitting"? Is it just a hissing noise?

 

Sounds like an air leak somewhere in the carbs , which seals itself up when the engine heats up and everything expands?

 

the problem with describing sounds in text is what you hear is not what i read. when you say spitting i hear a brief sound like someone expelling a bug that just flew in their mouth. is it that or a constant hiss like a leaking tire? the constant hiss could be a vacuum leak or the sound of air passing over the throttle blade. if it is more of a brief sound like what i hear as a spit sound it could be small misfires or a valve timing issue.

 

Agree totally, and what you're describing sounds like a backfire, which points towards timing/inlet valves.
When you say it happens more frequent when she's cold, is that with choke on?
A unqualified suggestion would be to tune her as per service, I.E. balance carbs, check timing and cam chain/tensioner.
If that don't cure her then check any vacuum issues on or around carbs, like cracks/leaks.
Then last but not least a leaky/sticky/burnt out valve.
Hope it's just a simple fix for ya.

 

It is not anything constant or hissing or whistleing. About every 5-10 seconds it makes a spit noise. Like something is building up and releasing. It comes from the carbs. Doesnt matter if the choke is on or not.

It mainly does it when the ambient temps are cool and the engine is cold. On a warm days it doesnt it, regardless of engine temp.

 

as mo777 and i stated it sounds like a timing or valve issue causing small backfires or misfires. i would do all he suggests, balance carbs, check timing and cam chain/tensioner, and also check/set the valve clearance. i've seen the clearance set to tight cause simular issues.

 

Could be a split boot too (between the head and the carb). Happend ot me and it wa srunning on 3 cylinders until it warmed up, then the gap/crack got small enough to bring that clinder back to life. Use a can of starter fluid and with small controlled bursts, spray it around the carbs. If the idle goes up, start looking in that area for the leak.

 

Thank you guys. I will order a carbtuner today. In the meantime i will try the starter fluid trick. Not sure how to adjust the valves. I will have to do some searching on this forum for a write up. Seems like i saw one some time back.

I do want to say I believe it is misfiring a little when it spits. I will run it again and listen back at the exhaust to make sure.

 

i built my carb tuner for about 12 $ in parts and use transmission fluid instead of paying 100$ for one...only one i might consider buying would be digital

about 25 ft of 1/8 inch clear plastic tubing, a couple of bags of sprinkler system 1/8 inch elbows and couplers a 4 foot 2by8 board and cable tacks. make parallel lines on the board about 1 inch apart for reference and tack the tubing perpendicular to the lines. tie all the tubes together with the couplers and elbows and fill with fluid.