Onan Valve Adjustment

[CTBT&D 77]

This is just informational, no questions or complaints. I have four Wheel Horses with Onan

engines and all run strong. Except the 1995 520H didn't run as smooth as the others.

 

Background on the 520H...

   - Bought March of 2011, 865HRS on motor.

   - I only use this machine to throw snow, now has 895HRS

   - The RPM's surged when got it, cleaned the carb with no problems since.

   - All regular maintenance has been done since 2011.

   - Checked cylinder compression, both in spec and even.

 

So I set out to do the valve adjustment (first time ever on an Onan). After removing everything

required (hood, air cleaner assembly, exhaust and intake manifold) I measured the clearance.

                           Intake           Exhaust

Front cylinder     .003"             .007"

Rear cylinder      .001"             .005"

Adjusted to         .005"             .013"

 

I don't know if this was from the original factory setting and the valve and seat wore to this point

or if somebody got in there and thought it was to loose and tightened the gap a bit. Back in the day

I have done adjustments on small blocks (Chevy and Ford), Honda and Yamaha motorcycles. I must

say these are easiest valves to adjust that I have ever done. Now it runs as smooth as the others.

Side notes: Checked the crankcase breather, and replace the oil fill tube seal while I was there. The

                   only issue was the throttle linkage from the carb to the governor arm. This had goofy S

                   bend on the carb end. I couldn't get it work right so I checked the other 3 running engines

                  and the linkage on those didn't have the S, but they measured the same length length to the

                  connecting points, 6 1/4". I have a spare 1992 P220 engine sitting around, so borrowed the

                  linkage from it and works fine.

 

I have to thank this forum for all the information I've been able find from time to time and when I've had

small issues to fix. Also have posted a couple of articles myself for information to others.

 

Thanks again,

Craig

 

  

[Martin 2,130]

good info there.....

referring to the gov/carb linkage, I've found the s bend link to be a pain, like you, i had a spare link with the clips on the end so i swapped it out. i think once the s bend ones start to wear they cause a lot of sticking issues with the pivot on the throttle shaft that it connects to. and if somebody has been bending on it, forget it.......!

 

happy for you you were able to report another success story.

[wrmhaste 235]

At almost 900 hours I would bet wear was the reason they were off. Their suppose to be adjusted every 600-800 hours depending on use of I'm not mistaken. My 92 has around that many hours and I just did the valves on that. Caught it just in time as the rear intake seat came loose and did very minimal,easily repairable damage.