I put a new Nikki carb on a B&S 14.5HP OHV engine and it still surges. It also backfires thru the carb about once per second. If I hold the choke flap 90% closed it runs smoother but still backfires say every 5 to 10 seconds. I have the fuel/ air mixture screw almost all the way CW, as if there is no more turning it CW. As I recall all the way CW pushes a small needle into a hole to restrict air flow. I think this is correct?
I just adjusted the intake valve to .005 and the exhaust to .007 before I ran it. The only other thing is I have the air filter assembly completely off, so basically you can see right into the carb. Not sure if this is adding more air to the problem or not?
I don't know what else to do with checks or adjustments. Does anyone have any ideas on this?
PS I have about a 10 second video of it running would this help to see it?