View Full Version : Kawi 25hp running on 1 cylinder

07-19-2007, 08:22 PM
Pulled each plug wire, and it dies with one, no change with other. Getting spark to the bad cylinder. Pulled valve cover, everything mooving as it should. Checked valve clearances - they were a bit big, so changed them but did not fix. Pulled plug on bad cylinder, and its dry...shouldn't it be wet after running? Took carb off and dissasembled and cleaned. At the end of my rope :(
Oh yea, started doing this 2 weeks ago, then ran OK since. I put a bottle of marvel mystery oil in fuel and its been fine until today.

Any ideas?

07-19-2007, 09:16 PM
When you cleaned the carb. did you also clean/flush the fuel tank and fuel lines then replace the fuel filter ?

07-19-2007, 11:22 PM
No, I just removed / dissasembled / cleaned carb.

Update...even though I had spark at the bad cylinder I decided to swap coils. After doing that it ran better but still died when engaging blades. Took off each plug cap and it ran worse with each one so that tells me both cylinders are working. Adjused all valves to .006" and now runs good...not great...still seems to have less power than it used to. Could the valve adjustment be that critical? They WERE at .018, now at .006 (hot). Maybe they should be somewhere in the middle at .012? It is backfiring through the carb under heavy load.

Its a FH721V 25hp Thanks for the response :)

07-19-2007, 11:34 PM
The correct valve adjustment should be .004"-.006" when the engine is cold. What gap did you set your coils at? They should be .008"-.016". Just split the difference and call it .012".

07-20-2007, 12:35 AM
Coil gap??? Uhh, I moved them all the way back (farthest from stator) and tightened them there. Didn't know they had a gap also. Looks like I'm taking it apart again...

I wonder if the lack of power/backfiring through carb is from the coil gap being too big?

07-20-2007, 12:44 AM
To set your coil gap center the magnet on the flywheel with the ignition coil. Then set your gap. It may well be causing the backfiring. I throws the timing off when they are not set properly. Your spark is also weaker when the gap is set to wide.

07-20-2007, 12:50 AM
use a business card to gap your coils

07-20-2007, 03:59 AM
use a business card to gap your coils

yup, that's what i did..works fine,actually used 2 pieces ripped from an oil filter box...just enough so the coil was not TOO close to the flywheel when spinning

07-20-2007, 01:09 PM
You might have a bad head gasket on the bad side. Take a compression test. Also make sure that your valves are moving the same distance when they open and close. You might have a bad cam issue. I have found that it is usually the exhaust valve.....

07-20-2007, 06:02 PM
Along with all that good advise, you might want to pull the head and check to see if the valves are seating correctly or if the valve seat has come loose.

07-21-2007, 08:34 AM
That is a Walbro WYK-186 carburetor. Take it back to the dealer, have him adjust it following the factory flowchart. If it fails to adjust properly & not stay set within emission limits, the dealer should replace the carburetor under warranty. This follows EPA guidelines, not just Echo. Yes, check all fuel lines & filter & carboned exhaust.

07-21-2007, 04:22 PM
Thanks for all the great info.

I swapped coils and it started running on both cylinders. Gapped the coils and she is running good again.

Thanks again.