Intermittent Engine problem.

[Ruben Rocha]

I have a 2003 Kaw FH721V with 1300 hours.
I just performed some general Maintenance within the last 60 70 hours.
Adjust valves, Fuel Filter, Air filter, clean & regap plugs, Clean and regap coils.
Drained the carb float bowl by removing the shut off switch and the drain screw. Tested shut off switch and circuit
Lubricate starter bushing.
Replaced the fuel pump ,Just because.
Plugs did not appear to be fouled when cleaned.
Also as a note I have never pulled the heads and de-carboned or re-lapped the valves.
Now to the problem. In the last week regardless if it is the first or last yard cut.
While mowing the motor stalls, sputters but never shuts off for about 10 seconds then the RPMS go back to normal once per day. It acts just like if you lifted up off the seat for a second. On at least one occasion I know it was not due to bouncing in the seat.
This happens once per day but never when I get back home to check it.
Also low idle speed during the day sometimes drops to about 1000 RPM which should be around 1550. when I get home to check it looks correct within 50 rpm. Upper rpm is set withing 50 60 RPM always seems fine during the day.

One last note I have noticed it has been slightly harder to start on occasion and seems to be flooding a little when starting.

Any ideas anyone. Possibly seat switch?
I did read something ROB posted about a compression release associated with the valves. Not sure if this feature is on this engine.
Should I recheck my valve adjustments?

I almost wish the thing would just break and stay broken so I could find the problem. So now I am down to being a parts changer in the interim.

[Ruben Rocha]

Still have not done anything yet.
But here is a update.
Today I go to the first lawn.
Start up and the engine is missing a little but seems to high idle okay. Cut the lawn . About 15 minutes. Pull the mower up on the trailer and the low idle is around 900 rpm. Then drive say 15 minutes to the second lawn. Start the mower still running bad. So I hesitate a few minutes to decide to cut or not.
Then all of a sudden the mower comes up to speed and runs fine.
Leave there and drive say 20 minutes and cut 2 acres and the engine runs perfect.

Go figure.

[Ruben Rocha]

I guess nobody wants to reply but here is another update.
I rechecked everything and I found one exhaust valve was about .002" off meaning to large a gap.
Been running for a few weeks with no problems at all.
Today I try a cold start on the first yard. As the starter is turning and turning it starts to backfire. It finally starts and will not idle at the correct rpms around 900 so I have to push the throttle some. After a few minutes. It runs fine and has the proper low idle rpm.
The plugs are not fouling at least when I check them after the fact.
Is it time to look at the carb?
Since I don't have a service manual I am thinking to just buy a new carb. But I assume it will need to be adjusted and I have no specs on it.
I am at the point that I don't want to screw with rebuilding it

[jkilov]

Hard to just guess something on a mysterious case like this.

Probably something electrical, like a damaged wire making contact with the housing causing weak spark. Check everything, clean, rub, refasten and use dielectric grease if possible. Coils are a common problem on kawa but this does'nt sound like one.

The fact you replaced the fuel pump sort of caught my attention. Again it's guessing.

[matt9923]

Rebuild carb? I didn't read every word but a small air leak or dirt in the carb will make it do some weird **** for a second every once in a while to barley running.
Ill keep thinking, iv had this happens a carb rebuild fixed it after i spent a lot of time looking into electrical and a bunch of other ****.
Matt

[matt9923]

Ok i read some more don't buy a new carb. Just rebuild it. Iv been threw over a 100 carb's and only saw 2 that needed to be replaced.
matt