656 pops when idling

656 gas runs ok with throttle open but when you put it up to idle it pops loudly every so often almost like it is backfiring. This is a new one on me. I thought it might be getting too much fuel. This tractor has the solenoid sticking out of carb but there is no adjustment on it unlike what the book shows. So is this a fixed jet now? Any ideas appreciated, Thanks

Hey Scott,

Backfiring is "almost always" caused by the primary ignition, which is allowing the spark to enter the exhaust system after the exhaust valve is starting to open.

I'd take a real close look at the points, their setting, any chaffed wires and also the distributor advance.

However, other things that could cause it include: ignition timing, ignition components, valve adjustment, sticking valves, broken valve springs, worn cam/gears or a burnt valve.

Just don't think your carb is causing that problem.

Allan

I have a 706G that works the other way. Carb frosts up something terrible. Going to go into the heat riser valve,it is now stuck.

Have you checked all the ignition components ? Could be moisture in the cap or carbon tracking, when running fast passes the problem area to fast??

Gas farmalls will miss once in a while at Idle (most gasoline engines will do it) when they do, they push unburnt fuel and air into the exhaust manifold. This ignites and makes a deep misfire/backfire type noise. If it has a flip rain cap on the exhaust, it will make it pop open and slam shut. If our tractors failed to do this, I would begin to look at the raincap to see if it was rusted up. Seriously if it runs well off idle, and is not a consistant cylinder misfire, ignore it, or consider it charming. Many tractors do not do it, but all mine, and the neighbors do. Fuel injection, electronic ignition/engine control, and modern valve setups in Automobiles have made many old sounds obsolete. JimN

I went through that and other issues with my 2606 which had the 1 3/8" throat carb on a C-263. It had the old solonoid with the wire long ago pulled out and the adjustment screw rusted & busted. They put an o-ring on the solonoid and adjusted the jet by screwing the whole solonoid in and out.

Went to buy a new solonoid and all they sell are the non adjustable ones which I didn't care to mess with the wire and also not really needed the shutoff. So I ordered the adjustable screw jet, nut, and packing and installed it so I have some adjustment. Have a fuel shut off on the gas line and I haven't had any trouble with dieseling which is what the shutoff was put on there for.

I don't think you have a carb problem with it running good wide open but I suppose you could take it apart and clean & blow out the idle jet and inner passages. Maybe check the float. If you remove it, may as well soak it in carb cleaner overnight before blowing out all the passages.

Especially before I fixed the carb and even now, I still use a full choke to start it. Mine used to pop and backfire when I pulled it back to idle. Don't really know what fixed it. Put new points and condenser and rotor and cap with no real help. It didn't have the symptons of a bad coil (coil getting hot, quitting after it got hot, etc) but when I changed the coil, all my problems went away and I can't really explain or know why. Later I added new plug wires which made no difference.

Is this something that just started happening on a tractor you've had a long time or is this a new to you tractor? Are you slamming it back to idle like a gas pedal would or are you/what happens if you ease it back to idle? These aren't made to race and gun like a car motor cause of the governor setup.

Let us know what you find out/provide feedback please. I'd like to know.

Thanks for the good replies,guys and to answer you bc, this is a new tractor to me, but it did not do this when I bought it,but started right afterward. I always run the throttle slowly and not too fast back and forth. Maybe when these terrible thunderstorms pass that we are getting in central Il right now,I can get out and check on some of these ideas and I will pass along what I find, Thanks

Thanks for the good replies,guys and to answer you bc, this is a new tractor to me, but it did not do this when I bought it,but started right afterward. I always run the throttle slowly and not too fast back and forth. Maybe when these terrible thunderstorms pass that we are getting in central Il right now,I can get out and check on some of these ideas and I will pass along what I find, Thanks

A couple of guys already mentioned a possible ignition problem. I have to agree. I'd check out the distributor cap for small cracks or carbon tracking first. Like Allen, I don't think it's your carb.