Honda UMK422 Trimmer


Old 07-23-08, 10:02 PM
Thread Starter
Join Date: Jul 2008
Posts: 2
Question Honda UMK422 Trimmer

My girlfriends father bought a Honda UMK422 4 stroke trimmer new in March 1998. He passed away in October 1998 so he only used the trimmer one summer. The trimmer sat in the garage until now. I took the trimmer to my garage and drained the tank, removed the carberator and cleaned with carb cleaner, blew out the fuel lines and cleaned the fuel filter, changed the oil, took out the plug and cleaned it. The trimmer fired right up. I let it run a few minutes then drained the oil again and replaced it. Started it up again and let it run for several minutes. It runs fine. Only problem is after running a few minutes and then when using the trimmer it begins to smoke quiet heavily. White smoke. Oil level is good. I have not ran it more than 5 minutes since it startd smoking. What could be the problem? The thing appears new and I would like to salvage it.
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Old 07-24-08, 06:49 AM
Join Date: Feb 2008
Location: usa
Posts: 755
Most Honda UMK422 trimmers came with Walbro WYL carburetors. Look closely at the carburetor to verify the carburetor installed. You should see WYL followed by two or three numbers.

I suggest you install a new plug instead of using the old one. A bad plug can often mimic other problems.

I hope you did not soak the carburetor as soaking can cause more harm than cleaning.

I have posted links to Walbro service manuals that you will need to correctly adjust the carburetor. The first link is the service manual for the WYL carburetor and the second is a general diaphragm carburetor service manual. Familiarize yourself with the WYL series carburetor by studying the service manual. The third link shows the gage which you get by without on the WYL carburetor.

In the WYL service manual it shows how to adjust the metering lever using the metering lever gage. This is a crucial adjustment. You can use the end of a ruler as a straight edge in place of the gage and follow page 6 step 5 of the service manual.

Good luck and post back with the outcome.
Old 08-01-08, 09:02 PM
Thread Starter
Join Date: Jul 2008
Posts: 2
Thanks Airman

Thanks for the input. I had not soaked the carberator. I only sprayed it lightly with cleaner. I went all over town looking for a new sparkplug. Didnt find one as of yet. I'll go to the local honda dealer and get one soon but I did get it running well and it has ceased smoking. I think the problem was is that I had used SF 10W30 and it called for SG. I found some 4 stroke SG and put that in and let it idle for several minutes before putting a load on it and it ran great and did not smoke. I did not realize there was that much differance between SF and SG oil. I really like the trimmer and the power it has. I have never used a 4 stroke trimmer. Always 2 stroke. This one is so quiet its great.

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