425 Problem

[MossRoad]

David,

All sounds correct except for misfiring.
PJ

The solutions for that condition are
:
A. Low idle fuel mixture is improperlyu adjusted. Adjust low idle fuel needle.
B. Float level is stuck too low. Separate carburetor air horn from carburetor body, adjust float per steps 4 and 5 on page 5.6.
C. Ilde holes plugged; dirt in fuel delivery channels. Remove low idle fuel adjusting needle. Clean main fuel jet and oil passages; blow out with compressed air.

On your carb, there is no adjustment for the main jet. There are two adjustements. 1. the low idle speed adjust and 2. the low idle adjusting needle.

To adjust the carburetor idle speed, with the engine stopped, turn the low idle adjusting needle in (clockwise) until it bottoms lightly. Do not force it in as it is easily damaged. Now turn the adjusting needle out (counterclockwise) 1-1/2 turns.

Start the engine and run at half-throttle for 5-10 minutes to warm up. Check that the throttle and choke plates can fully open.

Place the throttle control into the idle position, turn the low idle speed adjusting screw in or out to obtain a low idle speed of 1200 RPM +-75RPM.

Turn the low idle fuel adjusting needle in slowly until engine speed decrease and then back out approximately 3/4 turn to obtain the best low speed performance.

Recheck the idle speed using a tach.

As for the float, I would check that, too. There is a long procedure for that. I can scan it in and send it to you if you like.

 

[SnowRidge]

Possibilities...

Wrong carb kit.

Tech did not install it correctly.

Governor linkage reinstalled wrong or bent.

Air leak between carb and manifold

Air leak between manifold and head.

Blockage in exhaust. (Did he remove the muffler? Your symptoms fit this case rather well.)

BTW, the service manual is on the Kohler web site in PDF format.

 

[MossRoad]

Possibilities...

Wrong carb kit.

Tech did not install it correctly.

Governor linkage reinstalled wrong or bent.

Air leak between carb and manifold

Air leak between manifold and head.

Blockage in exhaust. (Did he remove the muffler? Your symptoms fit this case rather well.)

BTW, the service manual is on the Kohler web site in PDF format.

I think he has a CH25. I cannot find the manual on line for that. That's why I bought one from my small engine shop here in town.

 

[pajoube]

PJ, If you pull the choke out a little does it make any difference? I have used the 20, 22, 25 HP Kohler's, on my Dixie Choppers, and keeping the fuel solenoid clean, and water in fuel was about my only problem. Recommend you take it out and clean it . Maybe the service guy did it for you .

I took the carb off and brought to the service guy. It was only two bolts and three rods to take off (one side only). I also put in a new fuel filter and changed out the oil filter and filter for the hydraulic system.
I will check on the choke tomorrow.
PJ

 

[J_J]

PJ. I was just thinking, were there any options for ordering the carb kit? I know it would be a pain , but if you get the chance check the number on the fixed jet, if the service gave you back the old parts. You might check the number from the old jet also to see if it is the same. Maybe even switch back to the old jet. You are definitely at a higher altitude than I .

 

[SnowRidge]

I think he has a CH25. I cannot find the manual on line for that. That's why I bought one from my small engine shop here in town.

You bought one? You could have downloaded one for nothing.

Technically, I believe it is a CH-730 variant. The service manual is available here.

 

[MossRoad]

You bought one? You could have downloaded one for nothing.

Technically, I believe it is a CH-730 variant. The service manual is available here.

When I received my PT425 back in 2001 the service manual was not available on line. Only an operator's (or owners, I don't have it in front of me) was on line. So I bought three books at the small engine shop.

That link you sent me has some differences to the manual I have. Mine has nothing about fuel injection or emissions compliant motors. It also has better pictures than mine in some locations, like the spring hook up on the governor, for instance. I will download it at home and keep a copy on the PC just for reference. Thanks.

 

[pajoube]

You bought one? You could have downloaded one for nothing.

Technically, I believe it is a CH-730 variant. The service manual is available here.

I tried to open file but unable.
PJ

 

[Bob999]

I tried to open file but unable.
PJ

The first time I tried the link it failed. When I tried it again it connected and the file downloaded successfully.

 

[pajoube]

Went on to the Kohler web site and clicked on problems and got connected to expert who gave this advice.

This is where you have to decide if the problem is in the engine or the transaxle. If the engine rpm stays pretty much constant, then I'd look at the motion belt system first. If the engine bogs down hard, like it's struggling to pull, then I'd look at the braking system first. If the engine loses a few rpm but doesn't seem to be straining, then I'd go to the transaxle. If the engine sounds loose, like it wants to over-rev or blows black smoke then pull the spark plugs and check their condition. If the engine just sounds weak, you may have a fuel delivery problem.

Personally, just from what you have described so far, you may have a transaxle that's not cooling. Check that the fan is in one piece and that the transaxle is clean. That fan is essential for the Hydrostat to work and grass built up on the unit can also allow too much heat to build-up which thins the oil in the transaxle.

Thought I would pass this info along for your input as well.
PJ