Engine bogging down after 30 minutes

Wesley Teston

New member
25 horse kohler / 8gpm Hydrotek 120volt system

Last night guys are working right along with no problems then machine starts bogging down and chokes it self out.

Today I drain gas tank and change out fuel filter thinking there may be water in gas somehow. Add fresh gas restart and still bogging itself down only when pulling the trigger.

Idles perfect, so I check to make sure coil packs are working and they seem to be working fine. Change out plugs and put new air filter on and fire it up. Runs perfect for 10 minutes then back to bogging down only when trigger is pulled.

After all that I take off carburetor and clean out gas in there and shoot some carb cleaner in. Start up machines and it runs fine for 15 minutes, so I thought it was fixed.

Just got a call from the guys, it is bogging down again after 30 minutes of washing...

Please help!!!!!
 
Get 2 of those see through spark testers and put them on. Run it until it starts to sputter and see if the spark is fluctuating. The coils could be going bad. Does it continue to run, only at a slower speed, or does it try to die? Might want to do a quick compression check on it too.
 
Russ helped me go through a series of steps while this happened to me on a Friday evening while cleaning a parking garage. Ended up being something very simple, the engine was vibrating my choke out just slightly which bogged my engine down.
 
Get 2 of those see through spark testers and put them on. Run it until it starts to sputter and see if the spark is fluctuating. The coils could be going bad. Does it continue to run, only at a slower speed, or does it try to die? Might want to do a quick compression check on it too.
Used spark testers to check coil packs but not while bogging down... When bogging down occurs it is trying to die.

If you stop the engine, does it fire up and run fine? What if you let it cool?
I will have an answer for you shortly.
 
Got my 19 KAI back from the dealer just as the mowing season was over, with the same power issue, only 120Hrs on it, bad coil (was weak before)......, changed plugs prior........worked for a while then lose power......It would run fine with blades engaged off the lawn, but if you move forward on a hill (not cutting) it would lose power, any work you ask it to do it would bog down, but no load it was fine most times..... I could smell the unburnt fuel from the exhaust after better inspection; at least with the mower the power requirement is gradual unlike the pressure washer at full psi and gpm at a triggers pull.

Other good questions from the guys, how many hours on it?
 
Could be some of the above problems, but I have had the exact same problem using gas with ethanol. Seems like at times maybe they put too much ethanol in it and it will come unmixed! If you still have it, look at the gas you drained out. If it has sat for 5 or 10 mins it will separate sometimes and the ethanol will settle in the bottom. Stir it up some and see if it gets cloudy looking. Good gas will stay clear. Seems that I have had this problem more often when I can't get nonethanol fuel and fill up with 10% ethanol fuel on top of nonethanol fuel. Don't ask me why, but it has happened 4 or 5 times now. The machine will start running like crap under load especially, then I can stop, unhook my fuel line and drain some. What comes out first almost always smells just like rubbing alcohol!! I drain it till it starts coming out clear yellow and smells like gasoline again. Fire the rig back up and after it has time to run whats in the bowl out, it runs perfect the rest of the day!

I have another rig with the same Honda motor and it has been fueled by 10% ethanol fuel (at the SAME store that gives the other rig problems) since before I started having this problem and it never misses a beat. I have an employee in that town that keeps his rig with him and we use both those rigs washing trucks on the weekends. I usually carry extra fuel for the rig that don't like the ethanol fuel, but sometime I have to get some at the store down the road where my guy fills his up.

Both rigs have the same tanks, both tanks have the fuel pickup about an inch and a half from the bottom of the tanks.

I remember when only the CHEAP gas stations carried the 10 ethanol fuel, now its getting harder and harder to find places that sell the nonethanol fuels. There is one station in Dyersburg that does, and we have a fuel company that I have an account with that has pumps on their lot for the farmers, trucking co., etc. Thats it within 75 miles of me! Small engines don't like the ethanol at all and I think that it will not stay mixed is the problem, cars and trucks, lawnmowers, etc. keep their fuel mixed up, but engines that sit still while in use can't.

I race dirt stock cars and some guys are using the E85 fuel, because it gives a little more power, is cheaper than $7 a gal. race fuel, and engines run bout 20 degrees cooler on it, but they have to keep test kits with them because pump e85 varies a lot. Sometimes it will be 75% ethanol and at times its 95%. On a race engine, if its jetted for e85 and you put e75 in it, it will be way rich and not run good. If you put e95 in it, it will be too lean and run hot and possibly blow the engine!
 
If you stop the engine, does it fire up and run fine? What if you let it cool?
If you turn off and fire right back up runs like crap still. Let it cool down for a few you will get some run time before bogging down.

Other good questions from the guys, how many hours on it?
3000+
 
Kohler v-twin acts like it's running out of horsepower

Heads up on a Kohler specific issue..

On most of their v-twins..
the key-switch is mounted inside the fan housing..
this exposes the switch to pressurized "ambient air"..
and if the machine has enough hours on it.. the key switch corrodes on the inside..
that makes the ignition coils finniky.. so it acts like it's running out of horsepower.

If it acts up when it's cold and humid,
but seems to run better later in the day..
replace the switch, and you're back to work !

..I guess Kohler likes to sell key-switches. Eh?

..Also.. because of the same reason..
if you have an older Kohler or Onan
..with the voltage regulator mounted on the fan-housing..
you will need to coat the connections with grease to protect them from corrosion..
Moisture is attracted to the aluminum housing and the terminals.

Do-It-Your-Selfers..
Don't avoid technical people .. THEY have experience you don't..
Get to know the technical guy in your area,
and BUY SOMETHING from him once in a while..
That way, when you have an unusual problem, he's willing to help you.
Respect the tech.
:{)
 
Heads up on a Kohler specific issue..

On most of their v-twins..
the key-switch is mounted inside the fan housing..
this exposes the switch to pressurized "ambient air"..
and if the machine has enough hours on it.. the key switch corrodes on the inside..
that makes the ignition coils finniky.. so it acts like it's running out of horsepower.

If it acts up when it's cold and humid,
but seems to run better later in the day..
replace the switch, and you're back to work !

..I guess Kohler likes to sell key-switches. Eh?

..Also.. because of the same reason..
if you have an older Kohler or Onan
..with the voltage regulator mounted on the fan-housing..
you will need to coat the connections with grease to protect them from corrosion..
Moisture is attracted to the aluminum housing and the terminals.

Do-It-Your-Selfers..
Don't avoid technical people .. THEY have experience you don't..
Get to know the technical guy in your area,
and BUY SOMETHING from him once in a while..
That way, when you have an unusual problem, he's willing to help you.
Respect the tech.
:{)

Good info Jerry!!
 
There are a lot of tests you can run to further diagnose. Try to get a dealer from this site on the phone and you can get a bit of a walk through.
In the mean time, I'd change the oil with the thickest, heaviest stuff you can find.
 
There are a lot of tests you can run to further diagnose. Try to get a dealer from this site on the phone and you can get a bit of a walk through.
In the mean time, I'd change the oil with the thickest, heaviest stuff you can find.

No, Kohler recommends 10W30 year round.
 
Went back and tested the coil packs while machine was running crappy and found the problem. Bad coil pack. Would test fine before machine warmed up properly. Parts should be in Monday.
If that doesn't work I would consider buying a new Kohler engine. Time lost is leaving money on the table and 3000 hrs isn't alot of hours for a Kohler but it's enough and if it's costing you to much time which =$$$$ then it might be time to buy new.

That engine will run you about $1800-$1900 including shipping
 
If that doesn't work I would consider buying a new Kohler engine. Time lost is leaving money on the table and 3000 hrs isn't alot of hours for a Kohler but it's enough and if it's costing you to much time which =$$$$ then it might be time to buy new.

Thank goodness for backups.... They keep you from running out and making impulse buys!
 
Thank goodness for backups.... They keep you from running out and making impulse buys!
Those impulse buys are where I used to get my backups! I used be sure to have the cash for a new "whatever" that I can install and fix the old for a backup. Then, I started browsing for gently used equipment to keep as a backup. If you don't need it for work tomorrow, it always cost less...
 
Went back and tested the coil packs while machine was running crappy and found the problem. Bad coil pack. Would test fine before machine warmed up properly. Parts should be in Monday.

figured.....,

just as my KAI was acting,...

good operation cold and after a couple hours of mowing, weak,......cool it she ran 100% (or did it?? thats what we thought, comparing the new coils now, I feel the 19HP KAI was putting out about 15 HP with the weak coils running good)
 
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