L120 Engine problems

[Grand_Pooba]

Hi all.
I have L120 with about 300 hrs on it and it's been running very poorly. The engine misses and pops constantly at full throdle. I saw that one of the plug wires was arching to the block so I relaced it with a new wire/coil which gave me alittle improvement. Since the grass is growing fast I decide to take it to the dealer. They've replaced the other coil, new plugs, intake seals, rebuilt the carb, checked the compression....and it still pops. There stumped..
Anybody else had this problem. The engines a 23hp briggs.

Thanks
Steve

 

[BATTY54]

Does the engine do this all the time, or only after running for a while? I have fixed a few with a plugged up vented fuel cap. It will create a vacuum in the tank and run lousy. Easy fix remove fuel cap carefilly pull out inner rubber seal and plastic baffel. Clean all the parts well reassemble. It is such a problem with the L series the dealer was not even taking the mowers off the truck or trailer when I was there one day, he just cleaned the caps and sent them on there way.

 

[Grand_Pooba]

I've read about that problem before on this site so I did check that out first.
It makes that popping noise right from the begining and only at full throdle.

Thanks for the responce.
Steve

 

[mullins87]

Did you ever figure out what was causing the problem? My dad's L120 is doing the same thing. I've already replaced one ignition coil, it was bad. But almost immediately after that, I noticed it was leaking oil around the base gasket. Well, last night I got the motor back together with a new base gasket and oil seal around the shaft. When I tried it out tonight, it started running just like before after about 10 to 15 minutes. I checked the spark on each cylinder with an ignition tester and they are good. I'm going to look at the fuel cap tomorrow just in case, but it just doesn't run like it's running out of gas.

 

[jinman]

Steve, when the engine starts running rough and popping, have you tried various choke positions? I have a LA145 with a 22 hp B&S. It started popping a bit after I replaced the float chamber needle valve with a new brass one. I'm not sure that has anything to do with the popping, but moving the choke lever to make the mixture richer will cause the engine to smooth out. After it warms up, the problem is mostly gone and the engine runs pretty good. If you choke it a bit and the the problem goes away, you've pretty much narrowed it down to fuel starvation and/or you need to make the mixture a bit richer.