DuroMax 440 smokes and breaks up

[KD9DOG]

I have a problem and am stumped, I put a 440cc DuroMax into my cart (Hyundai) it went quite smooth I was surprised until I started the engine then things went South. While it was running it puked out a pint of oil from the pulse pump and that was caused by a droop in the vacuum line which I have corrected by raising the pump which lets any oil drain back.
Next took it out on the road and it idled just fine but when you stomped on it the engine sounded like it was a hit-and-miss going bad, broke up really bad thought it might be a bad carb gasket but that was not the case.
The only thing I have done to this engine was drill a hole in the crankcase for the pulse pump what is causing this erratic break up.

[raydhd]

A hole in the crankcase is not a good way to power a fuel pump on a clone. You have to remember this engine is splash oiled and the oil is everywhere in the crankcase. The usual method for the pump is either a carb spacer or a fitting in the valve cover. My suggestion would be to plug the crankcase tap and use one of the more traditional methods and see where you are.

[KD9DOG]

I did quite a bit of research as to where I can get the pulse and a good percentage used the crankcase, the engine that the Duramax replaced was a Hyundai engine of about 8hp and it was set up the same by using a fitting in the case with a hose down to the filler cap and then up to the pump. Only reason for replacing the engine was the factory eng was shot and parts were unattainable.
This does not explain the engine running so ragged only thing I can think of is it might be a Cal carb.

[CharleyL]

I know nothing about your kart or engine, but have a suggestion.

If you have electric power, you could use an automotive electric fuel pump. They maintain constant fuel pressure to the carb at all speeds. I installed one in my Cushman Truckster four years ago and it never ran this good before. Vacuum operated, and even the old mechanical fuel pump that was on my engine (now unobtainium) are nowhere near as reliable as these electric fuel pumps. A power wire from the key switch and ground are the only electrical connections. Put a good filter between the tank and pump and locate the pump low near the level of the tank and they will run trouble free for many years. When you turn on the ignition, wait a few seconds for fuel pressure to build, and then start it. My engine needs a little choke when first started cold, but the rest of the day it will start running in about 1/2 revolution without choking. The pump only operates to keep up the fuel pressure to the carburetor, so does not run constantly.
Maintaining the fuel level in the carburetor float bowl keeps the fuel/air mixture constant, and the motor running smooth.

Charley