Hi,
This has been a problem for a while with my Nikki carb 12a, but never has it been so bad. Usually if my car has not been started for a day or two, when first started with the choke out at about 2000rpm the engine would sound like it is runnig on one rotor. The exhaust note is very blatty and the engine very slowly with no power. But when slighthy warmer you can rev to about 2500rpm and it feels like the other rotor sort kicks on and off. The exhaust goes normal then blattly and normal and it revs like normal again. This would usually only last about 1 min or less. But now it is like this right up untill its warmed up and you even have to drive it a bit and get the revs up before it clears it self up. When cleared up the car idles great. When the engine is warmed up and the choke is off the car will still idle with this problem but it idles at 500rpm and sounds like a harley. pop, pop, pop, pop. I dont know if this is a problem with the carb or a valve somewhere or what.
Please let me know if you have any thoughts or have had any experience with this.
Thanks

 

how many miles on the engine?

 

Have you checked your intake manifold gasket? You can have the same type of problem if you have a leaking gasket or an o-ring.

 

how many miles does it have, and check for vacuum leaks my car sounded like that when their was a vacuum leak.

 

check your plugs mine does the same thing when the plugs start to get dirty/fouled. pull the plugs, give em a good cleaning and it will probably clear it up.

isaac

 

Might be fouling the plugs due to over-choking. Try backing the choke off a bit once it is running, but replace those plugs first.

Secondly, make sure that you have good spark on all plugs after you've replaced them.