14hp Kawa runs well for a while....then terrible. Help!

[Wayne Offiler]

48" Skag has 4 year old engine. Runs great for half hour or so, then starts to run ragged and loses power. Getting fuel and spark ok. Dealer thinks has been sucking in dust and dirt, and the intake valve is damaged. I hope its something less serious. Any thoughts?
BTW can someone tell me the correct plug? I checked an Intertec manual and it says Champion CJ8; no way! It's the FC420V. Thanks for any input.

[Robert Doubrava]

I would think a J19LM or larger. CJ8???? A little too small!:)

[BoogieDog]

Seems I have the same engine on my Scag and have never noticed such a problem. Will be interested in knowing the problem. I'd want to know if the fuel is clean and that your fuel filter is not clogged. Are you sure the air filter is OK? Sounds like a fuel/air problem to me.

[KenH]

Try changing the fuel filter, might be some water in there and as the engine pulls for fuel, it gets water, therefore rough running. Its worth a $3.95 shot.

[dynodp1]

or possible fuel system vent problem.. either a bowl vent or more likely tank/gas cap venting

[LAZERMAN]

It sounds like you either have a filter or tank vent stopped up. Next time you run your mower if it starts to run funny, loosen the fuel cap, if that helps change the cap. If it dosen't replace the fuel filter. The book is right about the CJ8 plug but when I get one in for service I always put in a J19LM, it's a little hotter plug and helps it run smoother. Hope this helps, write back and let us know. Later

[Wayne Offiler]

Problem turned out to be tank cap not venting. Wow, sure beats a bad valve!
By the way, Lazerman, I dont see how the CJ8 or J19LM plugs are proper. Mine is a real long reach (some AC #), and looking at the threads in the block, looks like it is designed for such a plug. Do I have a wierd Kawa?

[bwiesner]

Plug is an N11YC champion or if you want the best buy a Nippondenso W16EPU. Later Butch