18.5 hp OHV Intek only run on choke when hot

B

bob22cn

Member
I've about a 15-year old Craftsman lawn tractor (917.275760) with a 18.5 hp OHV Intek engine (engine model 31p777-0299-e1) that only runs on choke when hot.
I can keep it running if I run the mower deck engaged as the momentum of the spinning blades keeps it running; if I disengage the blades, it will die on choke.
This started last year and I thought it might be valve clearance so I adjusted valves over the winter.
Same issue this year; I redid them a week ago and same symptoms. Hopefully, I did it right, some concern about which valve is ex vs intake but I'm pretty sure I got it right:
upper valve5-7 exhaust valves
bottom valve3-5 thousandths intake
The carb has a restriction of adjustment of the mixture and changing it doesn't seem to help much.
I haven't taken off the carb bowl yet as I don't see dirt as a problem since it runs well for about 30 minutes and then starts acting up.

I'd appreciate any thoughts on how to investigate/fix.
 
The reason it runs better with the blades engaged is it's running on the main jet under load and the throttle is Wide open, i'm thinking the low speed/idle passage is blocked.
OR, the first thing i would try, get it hot, and when it starts wanting to die, loosen the gas cap.. if the problem goes away, the tank is not venting properly.

Small Engine, Lawn Mower, Snowthrower Troubleshooting, Repairs and Safety

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would you mind posting the engine date code, which is the series of numbers after the Model and Type numbers you posted, as this engine used a Walbro Carburetor and a Nikki carburetor.
 
Scrub,
the other numbers on the engine:
5bsxs.5012vp 276016

I thought about the gas cap but forgot to try that last time. I'm going to cut grass tomorrow, so I'll give that a try assuming it acts up again.
 
Those are the EPA numbers, the numbers i mentioned will be stamped near where you found the engine model number.
On the valve cover.
similar to this
1626210918204.png
 
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