Stumble/backfire when accelerating

[Mnethercutt]

Having what I think is a fuel issue w/ my 1010 gas. Tractor tends to stumble and backfire when I accelerate. I can improve or worsen the problem by adjusting the fuel mix on the carb. If I open the adjustment the stumble is better, but the tractor runs rougher and has a little black smoke out the exhaust. Exhaust also smells strongly of gas which makes me think it's getting too much fuel. If I screw it in the tractor runs stronger (at least it sounds stronger) but backfires a lot and almost dies when I try and accelerate from idle.

I've really only tried adjusting that fuel screw, but what do you guys think? Should I just let it run a little rich but backfire less? Got fairly new plugs in it, not sure about status of the points. Engines out of a power unit so it just ran at a constant speed when I got it.

Thanks a ton guys.

 

[jerseysierra]

Check points and also plug wires. Ignition is easier at idle, loaded ingition is harder and sometimes just enough harder to cause symptoms you describe if plugs, points, or wires not up to snuff. I am far from an expert, just my two cents.

 

[rustred]

do a compression check. you may have a burnt valve or need a valve adjustment. a carburetor does not make a backfire.

 

[Mnethercutt]

(quoted from post at 18:27:58 03/08/20) do a compression check. you may have a burnt valve or need a valve adjustment. a carburetor does not make a backfire.

Ok so checked the points and gave em a little cleaning. Didn't improve the stumble but it does start faster now so that's nice.

I don't have a compression tester and the auto zones was already rented out. However, I noticed some smoke coming out near the manifold so I shut of the tractor and cranked the bolts down more, and that significantly improved the problem. It still stumbles occasionally when I accelerate but the backfire stopped. I guess when I swapped the manifold I didn't torque the bolts down enough? I didn't see a spec in the manual and didn't want to crack anything so I stopped pretty modestly. Anyone know how hard I should screw those down?

Thanks!

 

[Jo Bird]

You might check the centrifugal advance weights and springs under the rotor of the distributor. If they are stuck or rusty the timing may not be advancing as it should.

 

[Jim.ME]

You can use a standard torque chart for a grade 5 bolt of the appropriate size. You may want to check it hot as well. You did install a new gasket when you changed the manifold, right?

 

[Mnethercutt]

(quoted from post at 15:26:26 03/09/20) You can use a standard torque chart for a grade 5 bolt of the appropriate size. You may want to check it hot as well. You did install a new gasket when you changed the manifold, right?

Yes, did use a new gasket

 

[RandyB(MI)]

Sounds like the throttle shaft /bushing is worn out and letting it suck air which leans it out and backfires. That's why richening the load helps it. That's the only thing that really wears out in these carbs. Also, FYI , the idle mixture screw on these adjust air and not fuel so turning it in will actually richen it and out leans it out.