Backfire

[rmm727]

^ I believe that's why they started putting those fuel solenoids in the bowls of the carbs on bigger engines now a days.

 

[zbuck]

One question, you stated that you welded pipe 1" black pipe to home made flanges. After the welds cooled down did you check them for flatness? If not they are probably warped and with used exhaust gaskets, therefore creating an exhaust leak. Therefore by sucking fresh air with un burnt fuel causing a backfire. Just a thought.

 

[chancer]

I had a Kohler in this mower I was flipping and it was so bad that every time you hit a bump and the seat safety switch killed the ignition momentarily it would backfire. It got so bad the dogs were scared every time you started any small engine.

 

[DeeJee]

I installed the mufflers yesterday, and it did help the back fire some. Fine tuning the carb solved a lot of the problem, but that and the mufflers did not completely do away with it. I will get a new carb kit later. The jack shaft came yesterday, so the time I can test the motor under load is just a short time away. I checked the RPM, and the motor idles good at about 1000 RPM. I didn't check the RPM when the clutch engaged, but would guess 1200 RPM, maybe a little more., The backfire is not bad if you ease into the throttle, and the same applies as you ease off.

 

[DeeJee]

Problem solved! One step forward, two back. As mentioned above, exhaust leak will cause this. I could detect no noticable leak, but had one. I retightened the flange bolts, and the motor now purrs like a kitten. It will pop when goosed, and let off in a hurry, but bearable. Biggest problem now is remembering to cut the gas off when not using. The gas tank is as low as I can get it, but outlet still slightly above carb, and it will siphonn gas in a heartbeat. Evidently gas is going throug fuel pump and carb straight into cylinder. Had to remove spark plug, turn over and blow gas out, then change oil and filter.
Thanks to all for the comments and advice. We are gaining.

 

[Desertduler]

If you are getting fuel in the cylinder then the float needle in the carburetor is not shutting the fuel off going into the float bowl and in turn flooding the bowl with fuel and then dumping the fuel into the engine, either shut the fuel supply off to the engine and start the engine and run it until it quits and then run the engine again and shut it off and see if the engine floods again if it does you will have to disassemble the carburetor and clean out the debris in the needle and seat, sometimes by running the carburetor float bowl dry and or draining it the debris can be dislodged and then the float needle will seal the fuel from overflowing the float bowl but the carburetor should be disassembled and cleaned and the fuel supply should be checked for contamination and the fuel tank cleaned out to eliminate this problem.

 

[DeeJee]

I realize the float is sticking. On this particular carb, you can replace the needle and float, but I do not think you can replace the seat. When I cleaned the carb, I took care to clean the needle very carefully, as the tip is neopreme. The problem is, when I lowered the fuel tank below the siphon area, I discovered the fuel pump was not working. So, I had to raise the tank back up. I can deal with the sticking float. It is aggrivating, to say the least, but as long as I remember to turn the fuel off, it works. Now I have a engine kill problem. There is a kill switch/diode mounted on or near the starter. I may have to remove the engine to access it. One step forward, two back. I am almost ready to roll. Only things left is the kill problem, and mounting the brake master cylinder, and hooking up the foot throttle. It is a good thing I am in no particular hurry.