I had a mechanic adjust the carb for a lower idle at normal operating temperature and after he adjusted the fuel mixture leaner I now hear an intermittent popping or puffing noise in the carb. Very low noise and it just started after the adjustment. Not all the time or constant. Hopefully not a lifter or valve issue. Any ideas would be great. Thanks in advNCE.

 

Take it back to the mechanic, tell him what's wrong and he should fix it. If he can't you might need to find a real mechanic......
It does sound like your idle is too lean.


Roger.

 

Popping or puffing noise in the carb?At idle.accelerating,at cruise,need more info.

 

First, a rough rule of thumb is that a lean mixture will backfire through the carb and a rich mixture will backfire through the exhaust.

Having said that, adjusting the idle mixture screws will change the mixture at IDLE and slightly off of idle. Once you open the throttle, the mains start flowing and the adjustment of the idle mixture screws is pretty much irrelevant. If the popping is at idle, then it might be the mixture screws. If it's at part throttle, it's something else.

 

Well, I took it for a test drive and it ran fine at 35mph and then decided to hit the big roads and hit 55mph. The engine ran fine for 1 mile and then started to stall surge etc. I did make it home and found that the vapor lock line to carb was loose. All vac lines are proper. I then decided to put the fuel mixture back to the richer mark on the dial. The carb sounded like it had fuel dripping a bit inside about a half hour after shutting it down. Not sure if my float is sticky or bad. Anyway, all this happened after a mechanic leaned the fuel mixture. Thanks for any ideas or advice.

 

Sounds like you need to go back the mechanic.

Are you talking about the side of the carb? That is the choke spring adjustment and does not affect idle mixture. Very misleading markings since it really just changes how long the choke takes to open. Idle mix is adjusted via two small screws near the carb base on the front side.

That sounds like heat related percolation but a high float can make it worse.

 

Still have not driven it yet after adjustments. The choke adjustment coil was what needed to be put back to a richer lean, I haven't started it to see if the popping noise went away. I also want to see if my float is messed up and if fuel is remaining in the bowl. I have a few tests for that as well. I appreciate the help.