V-twin Honda mower won’t run when warm.

This is on a cub cadet zero turn.
It starts right up and mows perfect for a few minutes then dies and won’t restart.
After 20 minutes it starts right back up. What I’ve done so far.
Changed both coils and spark plugs. Cleaned gas tank, lines and carburetor. I’ve ran it with the gas cap loose.
Tested the fuel pump.
Added new non ethanol when I cleaned the carb.
I’ve cleaned every electrical connection on it.
I’m wondering if maybe a valve starts sticking when it gets warm?
I can’t tell if it’s running out of gas but I truly believe it’s electrical.
When it tries to start when warm it sounds like the timing is off and has a bit of spark knock and an occasional backfire. When cool it starts and runs perfect.
I’ve also wondered about the fuel solenoid.?

Edited by Dave H - 15 May 2022 at 7:07am

This has no rubber tip on the solenoid rod. Just a metal taper. It has a removable plunger. I could try that.
I can not find a low oil switch on this motor.

steve(ill) wrote: pull a spark plug and see if it is sparking when hot.

Got two hours out of it this morning before it quit.
I did test spark with a screw driver. It seems to be firing but possibly intermittent?
Broad daylight hard to see the spark.

DMiller wrote: Adjust the valves.  Gets hot and clearances are closing up where valves are likely staying partially Open.

I believe this is exactly what’s happening.
Will adjust them tonight.

I pulled the valve covers last night. The valves were in spec per the manual.
I reckon I’m on to the next phase of this nightmare.
Gonna get some marvel mystery oil and run in the gas and see if a little top end lube may help.
She was able to mow 2 hrs without it dying last weekend but it was much cooler that day.
Pulled the plugs.
They look good but possibly a little lean.

jay may be on to something.. Maybe the carb gets hot and gasoline  VAPOR LOCKS ?  See if adequate air flow around the carb ... no restrictions... no extra covers.. ? .......... assuming you DO have a spark ?

dang... I ain't got too many more straws to pull outta my magic hat.....

This wouldn’t happen to be a 20 hp vertical?

coil?

make sure the gas cap vents

Thad, I wish I could help but I had that exact motor on a landpride razor that did the exact same thing, although it would only do it when it was hot outside, at least 95 or more, if there was no wind then it would do it at lower temp.  I had dual tanks and could switch back and forth and help but not solve, I never figured out what the cause was, but I was almost certain it was a vapor lock issue.  I guess I really gave up because usually it was hot enough out that you didn't want to be on a mower anyways, so it was a excuse.  Mine was new enough that it had the black outer plastic cover, but my neighbor had same mower older red metal cover 20hp and it wouldn't do it.  I was almost at the point of putting a fuel can in the freezer and when it did it pour that fuel in or try rapping the black fuel tanks in white.  I changed fuel line routing checked everything, got nothing.  I don't know if that's your problem but I felt fuel was mine, just never got it figured out.  Have you had this mower a while?  I can't remember now but I think mine started first year or two I had it.

Kansas99 wrote: Thad, I wish I could help but I had that exact motor on a landpride razor that did the exact same thing, although it would only do it when it was hot outside, at least 95 or more, if there was no wind then it would do it at lower temp.  I had dual tanks and could switch back and forth and help but not solve, I never figured out what the cause was, but I was almost certain it was a vapor lock issue.  I guess I really gave up because usually it was hot enough out that you didn't want to be on a mower anyways, so it was a excuse.  Mine was new enough that it had the black outer plastic cover, but my neighbor had same mower older red metal cover 20hp and it wouldn't do it.  I was almost at the point of putting a fuel can in the freezer and when it did it pour that fuel in or try rapping the black fuel tanks in white.  I changed fuel line routing checked everything, got nothing.  I don't know if that's your problem but I felt fuel was mine, just never got it figured out.  Have you had this mower a while?  I can't remember now but I think mine started first year or two I had it.

bought in late 2017.
Red main engine color the rest are black.
I do feel that re-routing the fuel line helped.

The carburetor may be getting hot and causing the VAPOR LOCK... the gas line can contribute to it.... But we have not discussed the gas tank location ?  Is there radiant heat on the bottom of the gas tank ?   Could it use an insulation blanket or baffle from the motor ?