Briggs Intek stumbles under load. What to check?

[Elkins45]

I bought a used mower, primarily to eventually scavenge the deck and transmission. It started and ran fine (of course) in the guy’s driveway but once I got it home the engine started giving me problems. It starts just fine and will run for a few minutes, but once you engage the blades it starts stuttering and missing badly. It smokes and smells like it’s blowing out unburned fuel, almost like it is badly out of time. If you disengage the blade it doesn’t recover but keeps sputtering and missing. If I turn it off and try to restart immediately it still misses, but if I let it set for a while it starts and runs normally. It’s an 18hp OHV Intek V twin from around 2005.

Any suggestions on where to start fixing/diagnosing? As I said I really bought it for parts but if I could fix the engine it would be nice to have a spare one of those as well.

 

[jeepman3071]

I would check the spark plugs and very their condition/replace them, then move onto the carburetor to make sure it is clean. Doesn't hurt to check the valve lash on those engines either.

 

[spasm3]

Check the carb jets. I had 24hp that the fuel line looked fine but was disintegrating internally, sending trash into the carb.

 

[Warstud]

Replace the Fuel Filter and add some Techron to the fuel

 

[ka9mnx]

1. Check spark plugs
2. Check choke

 

[blufeb95]

Replace the Fuel Filter and add some Techron to the fuel

I'll see how it does long term, but I've been using this in my OPE gas the last two years since I got a bunch of it due to a Walmart mishap. I use about an ounce in my five gallon fuel canister.

 

[Warlord]

Likely a carburetor restriction. Will likely need to be taken apart and physically cleaned.