Kholer Courage 25HP Vtwin stalls when warm and under load

[lcantu]

Im trying to fix an issue with this Husqvarna 54" riding mower with the Kholer Courage 25HP Vtwin

Symptoms

• Mower starts just fine and sounds perfect when starting cold
• I can engage the deck and mow grass for about 15 minutes without an issue
• After 15 mins and specially under heavy load the engine starts to surge and eventually stalls
• If i catch it early enough when it starts surging an I disengage the deck and reduce the throttle, it sometimes avoids stalling, and if i leave it like that for like 2 mins, I can set everything back to normal, re-engage the deck and it will mow for a few more mins before surging/stalling again

My situation is good because i happen to have another mower with the same engine which means i have a known good part for everything that I can replace. Given the symptoms, i was almost sure this was a fuel delivery problem so started swapping things there but I have gone quite far and I'm still having the same problem

This is what i have replaced already

• Carb
• Airbox with filter (the one that sits in front of the carb)
• Fuel filter
• Fuel pump

At this point i ran out of fuel related possible issues so i follwed by replacing

• Coils
• Sparkplugs

Nothing has made the problem go away and I have ran out of ideas of what could be causing this issue. On a sparate note, this mowers gets HOT like way hotter than my other one, not sure if this could be related at all but, still mentioning it.

Any suggestions on where could i go from here?


Hi everyone,
I'm trying to diagnose a persistent issue with my Husqvarna 54" riding mower and could use some guidance.

Symptoms:

• Starts and runs perfectly when cold
• I can mow for about 15 minutes with no issues
• After 15 minutes and when under load, the engine begins to surge and eventually stalls
• If I catch the surge early, I can sometimes prevent stalling by disengaging the deck and lowering the throttle. After idling for ~2 minutes, it will run normally again for a few more minutes before repeating the same symptoms
• Noticed this mower runs significantly hotter than an identical unit I own—might be unrelated, but worth mentioning

What I’ve Tried (using parts from a known-good identical engine I have):

• Replaced:
  • Carburetor
  • Airbox w/ filter
  • Fuel filter
  • Fuel pump
• After exhausting fuel-related suspects, I moved on to:
• Ignition coils
• Spark plugs

Despite all these replacements, the issue persists. I'm officially out of ideas and hoping someone might point me toward a less obvious cause for the issue.

Any suggestions on what to check next would be greatly appreciated!

 

[ILENGINE]

Depending on year of mower there is the possibility of a clogged fuel cap vent. Also there could be debris in the fuel tank that is stopping fuel leaving the tank. After those things check out. I have seen a couple cases were the heat shield that should be covering the exhaust manifolds is bent upward directing the exhaust heat directly on the carb causing the fuel to boil in the carb bowl leading to vapor lock. If it is a fuel boil issue you may hear the fuel in the carb bubbling. And also you won't be able to hold your hand on the fuel bowl due to being extremely hot.