Mower engine troubles. Please help!

I’m not sure if this should go here or in Off-Topic. Feel free to move it as needed.

I have a small engine issue that I was wondering if you guys could help me figure out. It is an Ariens lawnmower (heavy duty professional grade) with the below pictured Kawasaki 179CC OHV engine.

It sat for quite a while and my girlfriend said it “just wouldn’t start”. She does lawn maintanence for a living so she is very familiar with using small engines.

I messed with it for a few hours today and got it to run ok for a bit with lots of yanking on the pull cord and some starter-fluid. I pulled the valve cover to see if there were any visible issues there. It seemed like one of them was a bit loose but I don’t know enough about that to try to tweak them.

I did notice that the throttle was very touchy about where it had to be to run. Above 85% throttle, it would run super rich and sputter. At 60-80% throttle it might run OK. At 60% or below it would go lean and die.

I let it sit for about 20 minutes to cool down before trying to restart it. I had to pull a bunch more on the cord but no-go. It did back-fire out the intake/carb a few times which didn’t strike me as too much of an issue since I’d sprayed starting fluid in there.

On one pull, it felt like something “caught” with a “clunk” sound and wouldn’t let me pull hard on it. Just a little bit of tension and the engine felt like it “slipped by” the obstruction.

After some thinking, I believe that one of the valves got stuck open, hense letting backfires get into the intake/carb. Later when it “caught with a clunk sound”, I think might have been the piston hitting that valve.

Just for the heck of it, I openned the valve cover again and one of the valve push-rods had fallen off its spring which I beleive reinforces the stuck valve theory. I couldn’t get the rod to sit right with the valve/spring to get it back in. Interestingly enough, it was the other valve from the one that felt loose.

I am somewhat handy around the outsides of an engine but my only experience with the engine guts is helping my dad rebuild a mower engine when I was 8. Damned… That was 2 decades ago. I feel old.

Do you think our mower is likely to be toast, worth a service call, or is it some easy fix that I’m not getting?

Thanks in advance.


I just got some more history on the mower from Jeni. I guess this mower is a possible “lemon” sold to her boss by a “shady tool shop guy with bad business practices.” He’d supposedly rebuilt this engine before selling it to them. He’d also charged them for an authentic Honda mower blade when he’d put on an obvious no-namebrand knock-off. Some people…

Bent push rod perhaps? possibly a damaged valve set if something “caught”. If it’s OHV look up “valve adjustment OHV” on you tube; some great videos out there… Just the very little I know about small engines…

Hi Brian,
I found the small engine doctor on youtube. Fantastically detailed small engine repair series including “send me your questions” option. Best instructional videos I’ve seen. He covers blade problems, too. Information you can trust on over 100 clear as a bell videos.
Search Donyboy73Channel on Youtube.
Enjoy, Pepe