Kohler 26hp surges and pops - why?

cutitall

Forum Newbie
Joined
May 30, 2018
Threads
3
Messages
4
Hello All,

I've got a Kohler 26hp, 747cc, 7000 series, KT745, V-twin on a Husqvarna zero-turn. It has a manual choke (cable type).

It has slowly started running rough. At all throttle speeds and when warmed up, the engine rpms surge up and down, and at full throttle it pops through the muffler a little bit. I have to apply the choke to start it even when warm. Importantly, if I give it some choke the rpms come up and the engine smooths out. If I dribble some carb cleaner down the carb, the rpms come up and it runs smooth as well.

Looks like I've got either a vacuum leak problem or a fuel starvation problem. I'm going to start basic troubleshooting, but if anyone has been through this with their Husky/Kohler already and fixed it, please let me know!

I had a leaky passenger side valve cover. I fixed that wondering if it was causing a crankcase pressure problem that was slowing down the fuel pump, but no help there. Leak stopped but no improvement on engine running.

Thanks for reading!

Cutitall
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
You are on the right track.
surging on a governed engine is always due to an fuel;air ratio that is too low.
Either air is being drawn into the cylinders after the main jet has added the fuel
or
The fuel supply to the main jet is not enough.

You test for the first by starting the engine and saturating the area between the carb & the engine with WD 40 or similar from a trigger pack, not a spray can.
If there is an air leak the goo gets sucked into the engine causing the revs to change & if WD 40 used, lots of white smoke.

As for the second, it could be anything from a blocked fuel tank vent ( checked by loosening the cap ) all the way through the fuel system to a blocked jet in the carb.

I like to use an alternative fuel tank ( pinched from a push mower ) hooked directly into the carb to isolate the mower from the carb as the cause.
Otherwise start at the tank and move through to the carb, cleaning & replacing defective fuel lines.
Remember it could be as simple as a build up of water or as complicated as softening fuel lines depositiong rubber all through the system.
 

cutitall

Forum Newbie
Joined
May 30, 2018
Threads
3
Messages
4
Old thread, I know, but I replaced the carb (after trying to clean the old one with no results) and it runs like a champ now. Just FYI.

Cutitall
 

slomo

Lawn Addict
Joined
Jul 14, 2019
Threads
76
Messages
4,677
Thanks for getting back here and letting us know. Someone in the future will appreciate it sir. (y)

slomo
 
Top