I thought it was just my HRX217 lawnmower that oscillates wildly during
idle. But then I rented a Wacker trash pump with a honda engine, and it
would also oscillate when in the full throttle position whenever it lost
prime. Then I rented a pressure washer with an 11HP honda engine and this
too would oscillate heavily at idle when the water was not being sprayed.
The fluctuation is pretty severe, as if the engine is going to stop, it
doesn't sound normal at all. Since it happened on 3 engines in a row - I'm
starting to think it could be the gas I'm using. My gas cans have a mix of
89 and 91 octane from Mobile. Could it be that the octane is too high? Am
I supposed to use 87 octane instead?
Could it be that all three engines have worn out parts? I suppose that
could be possible since two of them were rentals that are subject to heavy
abuse. But the other one, my HRX217 mower started doing this after only a
few months. So it was practically brand new. Is it just my luck with Honda
The interesting thing is that all 3 of these engines would run great under
normal load (while cutting grass, while pumping water, while spraying). The
fluctuation only happens at idle or under non-operating load.
I believe that's what the engineers refer to
as the governor hunting. There must be some
way to increase the hysteresis of the speed
control system for those engines. I've seen
a lot of small engines fluctuate under non-
load conditions and sometimes something as
simple as a new muffler will straighten it
out. When my friend's chainsaw was running
poorly, surging and such, we got the manual
out and adjusted every needle valve on the
thing by the book and it solved the problem.
When I took my small engine repair course, the teacher
called that "hunting". As in "hunting for the proper speed".
The problem is typically that the spring for the governor
gets rusty, stiff, painted, etc. The governor spring is far
more essential than people understand.
I tried a new air filter, changing the spark plug, changing the oil. I
looked for any mixture adjustment screw but I was told that the HRX217
doesn't have such adjustment. Anything else I can check? It started
happening when it was relatively new after just a few months so it would be
less likely to be an air leak or rusty spring etc.
I should have said. " I've seen oscillations from running small
engines lean." Not specifically the Honda. I never looked into a
carb adjustment, don't even know if one exists because the new
air cleaner solved the problem.
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