misfire and backfire

[bigal_11]

I have a Husqvarna YTH24V48 Mower with a Briggs 24 HP Intek V-Twin engine. Early this mowing season it started getting hard to start and would only start with a short spray of starting fluid. It ran great after it started until about a month ago. I still have to start it with the fluid but now it has a misfire and backfire when blades are not on. When blades are on it does not backfire but does still misfire some but not as bad as when they are off.

I've checked the adjustment on the valves twice. The first time they were slightly out of spec but not bad so I adjusted them to within spec. The second time was just to double check my work. No adjustment needed second time. I've changed plugs & air filter. The plugs looked good, no discoloration or burning, but replaced them anyway. I replace plugs every spring along with oil change, air filter and fuel filter before I even start it for the first time.

I have about 180 hrs total on the mower and I got it new about 5 years ago.

Does anyone know what my next step should be?

 

[bertsmobile1]

The carb is blocked in the idle circuit .
Probably been that way for ages .

 

[enigma-2]

I've had the same problem years ago (same engine) and solved it by adding Sea Foam to the gas. Ran the engine to pull it in then shut it off and left it sit. Tried over several days and finally clog dissolved after 5 days. (May have been 6). Doesn't always work, had one that refused to unclog, took to dealer and he used ultrasound. Finally disassembled and cleaned all jets with wire. But for most clogs, Sea Foam will help.

I now add a small amount of Sea Foam (as well as Sta Bil) to every gas fill up. Seems to work, my generator sits year after year with Ethanol gas and starts easily and runs fine using this mix.

 

[bigal_11]

Thanks guys. I'll give the seafoam a try. I use sta-bil on a regular basis already but never seafoam.