I have a carb issue and I am not sure if I am diagnosing it right. I have done some searching, but what I found doesn't really address the issue I am having.

I just bought this quad knowing it was running rough, meaning that it wouldn't idle and would not run with the choke off. However, I would say my mechanical ability is advance so I figured I could fix it.

I removed the carb, pulled off the bowl, main jet assembly, slow jet, pilot screw (which was 4 turns out)float & needle along with the air cut off valve. Everything was cleaned and blown off with compressed air. However, this did not cure my problem.

The quad will not run with the choke off. With the choke on it will throttle up, but of course there is no power. It will idle some what, but if left alone it will die. With the choke off you really have to jerk the throttle just to keep the motor running. With the throttle just off idle it spits and spatters and kicks back through the carburetor. If you come off the throttle the engine will die and not idle. Also, while I was keeping the motor running with the choke off the headers got cherry red. Of course this is a lean issue, but my brain is racked and I don't know anything about this carburetor.

The quad it bone stock. The main jet is a 148 and the slow jet is a 38. I have read on this forum that it is suggested to change the slow jet to a 42, but is this the case on a stock motor?

I put in fresh gas and then replaced the spark plug. It is still acting the same way.

Thanks in advance for the replies and help.

 

not wanting to idle can usually be tracked down to a couple things.....one, your idle speed is way too low, have you tried turning that up? and two...the pilot (or slow jet) was plugged up, or the passage that goes from the pilot to the carb throat is plugged. My son's 300ex ( same carb, just smaller) sat for a couple years, and would not idle without throttle and lots of choke,I had to take a wire and drill out the pilot jet, plus blow out the passage with carb cleaner to get all the junk out. once it was cleaned up, it started and idled fine. The bowl and the rest of the carb can be spotless, but without the fuel from the pilot circuit, it will not idle, and will start and run like crap.

 

Not to much I can add besides the fuel air screw is usually around 2.5 turns out.
The 40 or 42 slow jet will helps with cold starts.

 

Thanks for the replies. It seems I have done everything and nothing is working. My only thought is, like you said, is the idle circuit has gunk I can't see.

I think I may try a different pilot jet. I can see light through it but the hole is very, very small. I have my pilot screw turned out 2 1/4.