Kohler pro 13 HP diagnosis

[jeffex]

This motor is 12 yrs old. This fall during leaf cleanup is noticed the motor would sputter , loose RPM , and belch some black smoke when under load mulching leaves. I use doulble blades with a mulch kit installed. I put on a new gas filter and used sea foam to clean out the carb. I removed the carb and cleaned it. the RPM under load improved but there was still some remnants of the symptoms. I am going to perform a compression test this weekend to see if I should simply get a new carb or rebuild the internals . My question to those in the know is ...am I on the right path here? I got the specs for compression from Kohler off their website in PDA format. I 've got all winter to play with this thing and 2 winters ago , with advice from restorob, I rebuilt the tranny on this mower. toro 36" W/B. A fun winter project!

[Restrorob]

am I on the right path here?

Well, You are getting there..... Have you replaced the spark plug ?

Could also be a coil breaking down under load, I would put a in-line spark tester on it then put it under load to make sure it's firing properly.

[jeffex]

no on the spark plug. thanks for the tip on the coil test. I'm working on it this weekend and that will be a good place to start as I have to remove it for the compression test. I put a new one in last year but anything can happen to foul it. thanks!

[jeffex]

looks like a compression test is out ACR automatic compression release! I need to do a leakdown test! the spark plug shows carbon deposits and can indicate any number of things. I have to get a inline spark tester

[NIXRAY]

Have you checked the air cleaner, and the cooling fins (if any) also check your exhaust, if either is blocked you could get these results.

[Restrorob]

I got the specs for compression from Kohler off their website in PDA format

I was wondering how you did this.

looks like a compression test is out ACR automatic compression release!

Since it does have this, But the leak-down test is much better anyway.

[jeffex]

checked the air cleaner first as the leaf dust is a problem. exhaust is flowing good. never thought of coolong fins but I will check..thanks...my son is an auto tech. and he brought home a compression test kit. Now I need the in line spark tester! I pulled the plug and the photo matched this ;
Carbon Fouled: Soft, sooty, black deposits indicate
incomplete combustion. Incomplete combustion is
usually caused by overrich carburetion, weak ignition,
or poor compression.
Once i test the ignition I can decide to replace it or the carb. If its the compression then I'll have to rebuild. I can get a new motor but this is more fun. I may F it up and STILL be getting a new motor but its a chance for hands on training. Any good sources for walbro carbs ? walbro's website says $78 for the carb

[Restrorob]

walbro's website says $78 for the carb


That's about the going price on these.....

[jeffex]

In my search for info on this motor I found a possible solution for my kohler 15 hp that looses RPM under load on another w/b mower. the govoner arm has 2 holes to increase or decrease the sensivity . I will try the other setting and see if it picks up RPM under load better. This mower has little hours on it and it had this problem almost from the start. It mainly happens in tall wet grass so I just solved the problem with a double cut. The mower did great 90% ov the time . I may get back the 10% in heavy loads thanks for your help ..again Restorob

[mowermankevin]

Jeffex, I have a 13 Kohler setting out here on a 32 Toro W/B and it's shot, so I look in the J. Thomas catalog and no 13 listed. So I go uptown to my good bud at the mower supply to see what a 13 replacement engine is and it's $200 more for 2 less horses, so when you price parts and your time and by all means tear into that engine,(that's how you learn) keep in mind the replacement parts cost versus a new 15h.p. in a box for $600. That engine stumble could be where the throttle shaft wears on the carb housing and wobbles out the housing letting the engine suck air, it's real common on high hour engines,especially if their not kept clean. Fall leaf pick-up is dirty,dusty and hard on filters and engines.

[topsites]

the govoner arm has 2 holes to increase or decrease the sensivity . I will try the other setting and see if it picks up RPM under load better.

You do so at your own risk but I run all my Kohlers on the other setting.
And yes as a rule it will increase rpm's, sometimes drastically (red line).

[jeffex]

Most likey $600 is in my future but not before I play around some. I'm going to try and rebuild the blade spindles too. If not I can get new ones. My plan is to strip the thing down , paint it and fix as much as possible . Even if I buy a new 36" at least this is a sound backup mower. Backup equipment paysfor itself in not loosing down time for equipment repair IMO