Kohler XT-7 (pressure washing) dying at sustained load/throttle

[92saturnsl2]

I have a 8-9 year old pressure washer with a Kohler XT-7 (173cc IIRC) engine that is having trouble running at sustained load. It just started doing this last time I used it, but the problem is consistent.

It will run fine at its normal RPM (no load), but when you hold down the trigger on the wand for more than 7-8 seconds or so, the engine starts stumbling and will quickly die if you keep it held down. If you let the trigger go for a few seconds, you can continue for several seconds and it will run fine until you hold it down too long. If I reduce the RPM the pressure washer will run fine under load for long periods, so I presume this is a fuel starvation issue.

No fuel filter on this unit. Is there anything in the carb worth tinkering with that could cause this issue? Or is it cheaper/easier to just replace the carb and hope for the best?

 

[tomcat27]

Gas tank vent?

 

[Driz]

Loosen that cap and see. Otherwise it's the infamous never ceasing plugged up carb venture. That tiny little plastic or brass tube an inch long above the fuel inlet seat has many microscopic holes across its sides that love to plug. Not sure Kohler has that design though but be aware for it. New carbs usually are cheap on Fleabay -$20 too.
To avoid most of the headaches get a pack of Fleabay 1/4" shut offs and Mount it in your fuel line, 5 are under $7. Shut it off with that if it's going to sit. At the least run it dry at seasons end, layup ect.
Here's what gas did to an under year old Toro bowl left with gas in it over the winter🤣

check out Project Farm on Youtube. He has an experiment on leaving gas in carbs on layup. Note none of the fuel storage additives really did much good !

 

[Donald]

Check the spark plug just because its easy. I have seen a gas filter screen inside a gas line. Governor?

 

[92saturnsl2]

Hadn't had time to look into this until today, but I took the gas cap off and that doesn't solve the problem.

I removed the air filter cover and low and behold when the engine begins stumbling, it's actually back firing out the intake. I get a couple-three good backfires where you can see flame/explosion right out the air inlet, then the thing dies. Not sure if that leads in a certain direction, I'm about to pull the carb off and dig a little deeper. Just wanted to post a quick update!

 

[92saturnsl2]

I took the carb off and gave it a thorough inspection and cleaning. The thing looked just like it came off the assembly line-- not a hint of varnish, gum or anything of the sort, it literally looks brand new. I sprayed all the passages down with carb cleaner anyways, none of the passages seemed restricted in any way.

There was a fuel filter screen inside the fuel line, I tossed that and put a traditional fuel filter on. Also checked the valve lash, they were a tad loose so I adjusted to spec. Spark plug was fine, tip was a little lighter than I'm used to seeing (light grey, almost white), perhaps it's running lean. Nothing else on the intake side to check so I bolted it all back together.

Problem is still there, but it doesn't do it when cold. I can spray for 2-3 minutes solid before it starts the backfiring. Once the backfiring starts it's consistent anytime you hold the trigger down for more than 2-3 seconds. If you hold the trigger down too long the engine falls flat on its face and dies.

One thing I discovered is if I close the choke almost to the point where the engine won't idle (just before), I can run the sprayer 100% and it won't die or backfire. But the engine runs a bit rough at idle with the choke at that setting.

Definitely has me scratching my head. I suppose a new carb would be the next thing to try?

 

[varmint]

I had the same problem on a Honda powered pressure washer. Plug looked OK, (about 50 hours run time) but changed it anyway.
Old plug NGK BPR5ES replaced with same. Engine ran perfect.

 

[andyd]

Are all the fasteners ,carb to intake to engine tight? Grey plug is tip off, It is running too lean for some reason, How is the float setting?