312-a with issues

[312hoss 0]

Hi RS members,I have a 312-a 1986 that has a problem.While running it will spit and backfire then cut off but will fire right back up.I have replaced the spark plug,points and condensor also checked fuel pump,fuel hose is new.I also made sure the fuel shut-off is clean,i even replaced the coil!Anyone have any other ideas of what to check or replace?Thanks for your help!Bill

[clyde 5]

valve adj.?clearance to close perhaps

[boovuc 1,090]

Does it run OK if it's just sitting still? If your machine runs Ok at full throttle sitting but "acts up" when you put it in motion, you may have:

1. A loose connection in the ignition or on a safety switch somewhere?

2. Gunk in the carb causing the float to shut off fuel.? (If it failed open, you'd see gas pour out the air cleaner).

3. Bad ground on the tractor?

4. Over heating under load? (Too lean).

5. The fuel pump may be pumping fuel but may be weak and not giving it enough under load?

I would seriously look at the connections overall on the tractor first. If you have an amp or charging gauge on this, look at the gauge while it's acting up. If it's jumping, look at your switch first thing! Next the safety switches then the rest of the ignition and the ground(s).

[Wheel-N-It 2,976]

Try giving it a little choke. If the problem goes away then you probably need to adjust the high speed needle to give it some more fuel. To adjust it properly, you will need to enrichen the carb a little at the time. Then give it a plug reading. After you get the engine running properly, start mixing a little MMO in the fuel. I always recommend 4 or 5 ounces MMO per 5 gallons of gasoline. It will help lube the valves, and keep the carb clean. BTW, you should also remove the carb and give it a good cleaning with a brass bristle cleaning brush.