Onan B48G - Bogging with Backfire

Any suggestions what may be causing backfiring out the carburetor then it runs OK a few minutes then back to bogging down and spitting gas.
John Deere 420 twin cylinder Onan engine. Replace plugs, wires, fuel filter, sampled gas from the bottom of the tank (no water), cleaned carb, adjusted float, new engine fuse, checked as much safety switch wiring as I could find.

Category:

Autos & Vehicles

Tags:

• Onan
• B48G
• John
• Deere
• poor
• idle
• garden
• tractor
• help
• backfire
• carburetor
• bogging
• engine

[WillyHeinExperience]

After adjusting the points it ran fine for a few months. A few weeks ago it starting acting strange again.

There is enough points material left so I replaced the capacitor (condenser) and it's running like a champ.

I used a capacitor from the local auto parts store and it's not mounted under the metal dust shield. I'm looking for an new location away from engine heat.

Thanks for the post, at first I thought it was a sticking valve or sheered flywheel key.

[Conanraaka]

Bad intake valve good luck

[sexyspacemonkey]

It sounds like as if your timing on your engine is totally wrong, and when it runs right thats just the engine warming up so its bound to get better, but as it adjusts it will happen again like you say, look up in you owners manual and have a look at the valve gap setting, make sure your engine is at top dead center, other than this i can think your valves are bunt out and need replacing. Hope you find the problem.

[mdlrr1]

I've got an Onan B43M that is doing the same thing but it also backfires through the exhaust as well. When I throttle up, fuel sprays up through the carb just like yours is doing. If you get it figured out, let me know. I spoke with one mechanic that says Onan carbs just wear out and putting a kit in doesn't always help. I hope that aint the problem cuz those carbs are very expensive to replace. Good luck and if I get it figured out, I'll let you know as well.