Kubota 125s begins to lose power after warm up.

D

doc craker

Member
Kubota 125s with Kohler 740 engine and 54" deck. 2017 model 253 hours.

This started last season. After about an hour of operation the engine will lose power when I have the blades engaged and I make a sharp turn or go up hill. Normal engine lugging in heavy grass. The real power loss is during the hill climb or sharp turns. I replaced the fluid and filters on the wheel motors late last year thinking perhaps the fluid was not flowing.
Is there a valve that is malfunctioning in the hydraulic system?

Only happens after warm up. About an Hour. Does not happen if PTO is not engaged. Replaced fuel pump and filter last summer. Engine loses power, does not cut out just runs slower.

Thanks
Doc Craker
 
Need to check for spark after the engine starts acting up to rule out an ignition module that is failing while hot.
 
This is a typical sign of a spark plug that quits firing or the ignition coil/module failing when hot. These engines do not shake or vibrate when a cylinder quits producing power.

A quick test can be done by spraying water with a spray bottle on each exhaust pipe near the head mounting area after the engine has run for a few minutes. see if both instantly burn the water off. If one does not, that is you suspect side to check further.

This could also mean it is time to perform a valve adjustment. Correct valve adjustment plays a vital role in balanced engine power.
 
nice tool. wish I needed one enough to justify cost.
Haven't forgotten the other tests. Waiting for the 4 days of forecast rain to pass.
Then it's Easter. I will get back to you.
 
doc craker said:
Kubota 125s with Kohler 740 engine and 54" deck. 2017 model 253 hours.

This started last season. After about an hour of operation the engine will lose power when I have the blades engaged and I make a sharp turn or go up hill. Normal engine lugging in heavy grass. The real power loss is during the hill climb or sharp turns. I replaced the fluid and filters on the wheel motors late last year thinking perhaps the fluid was not flowing.
Is there a valve that is malfunctioning in the hydraulic system?

Only happens after warm up. About an Hour. Does not happen if PTO is not engaged. Replaced fuel pump and filter last summer. Engine loses power, does not cut out just runs slower.

Thanks
Doc Craker
Click to expand...
If engine is losing power when making turns, or going up a hill, a possibility is there is debris clogging the fuel outlet from fuel tank. Remove fuel hose after fuel filter and blow back into tank with air compressor and blow gun (fuel cap also removed).
 
ok gang.
Finally had time to check out your suggestions.
One of the cylinders is not firing. Hard to believe that a 2 cylinder engine would still run smooth after dropping a cylinder.

Anyway, we have a diagnosis and now what it the treatment plan? Remember I am a doctor not a mechanic. lol.
So, take it easy on me.
Thanks in advance.

Doc
 
Hello D.,

You need a small engine spark tester that has an adjustable air gap (eBay or Amazon has them). Do not use a flashing bulb type because they are not reliable or truthful.

Attach the tester to the plug wire them ground the clip lead on the engine block. Crank the engine and watch for spark to jump the gap (most spark testers have the letters SE to indicate where to set the adjustable gap.

If both coils seem to be firing a nice blue spark, then it's time to question the valve adjustment on the engine.

Let us know what the spark tester indicates before we move on.
 
ok auto doc's.

all I have is the bulb type. You attach it to the plug and then the plug wire. Not reliable?
OK . I will order the other one. Do happen to have a link or good description of the tester?
 
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