PT 425 - repower options (Kohler 25hp)

[Modrob]

I’ve just discovered I’m in the same boat. (Looks like I’ll have to replace or rebuild our CH25s in the PT425. It’s about 24 years old and has done a ton of work before me. Yesterday I found it has gas in oil, one cylinder at 90psi, and the other at near 0psi. And, it still has that old, troubled coil/flywheel system. I’m thinking it’s probably more efficient to replace it, and I too am going to call Tazewell and ask about their options)

 

[m5040]

Probably the best in the long run. They are such versatile machines. If the rest of the machine is OK, it would be well worth it.

 

[m5040]

I’ve just discovered I’m in the same boat. (Looks like I’ll have to replace or rebuild our CH25s in the PT425. It’s about 24 years old and has done a ton of work before me. Yesterday I found it has gas in oil, one cylinder at 90psi, and the other at near 0psi. And, it still has that old, troubled coil/flywheel system. I’m thinking it’s probably more efficient to replace it, and I too am going to call Tazewell and ask about their options)

I guess you have a few post on this problem. One thing I would do, since you are changing the engine anyway, is to have some fun doing some quick off-the-wall repairs with the original engine. Start with checking the valve rockers under the covers to see if everything is in the ballpark and see if you can get a rudimentary check on the timing. Then gravity feed the carb with a plastic shut off in line and make sure the fuel level is higher then the carb. Put in 40W oil and try to start it again.
The negatives are that it should have attempted a start as it is now when using starting fluid, so it may have jumped time somewhere. The 40w oil might/should bring up the low side compression because the oil helps the rings to seal and gas diluted oil won't.
Might be worth a try.

 

[2manyrocks]

I replaced the Kohler v twin in my Terramite some years ago because it was the easiest route, but I've always thought a diesel engine conversion would have significantly improved its performance plus the gas engine has always seemed to use more gas than the diesel in my Yanmar 226d seems to use.

With new 25hp gas engines hovering around $2,500, a conversion to a used diesel engine might be worth considering if you could copy the conversion agjones did.

 

[Modrob]

I guess you have a few post on this problem. One thing I would do, since you are changing the engine anyway, is to have some fun doing some quick off-the-wall repairs with the original engine. Start with checking the valve rockers under the covers to see if everything is in the ballpark and see if you can get a rudimentary check on the timing. Then gravity feed the carb with a plastic shut off in line and make sure the fuel level is higher then the carb. Put in 40W oil and try to start it again.
The negatives are that it should have attempted a start as it is now when using starting fluid, so it may have jumped time somewhere. The 40w oil might/should bring up the low side compression because the oil helps the rings to seal and gas diluted oil won't.
Might be worth a try.

Oh for sure! LOL First, my curiosity is harping at me to dig in and see what has actually happened. Luckily, we don’t use it very much (I picked up a 1950 IH gas crawler/dozer several months ago that is FUN) so I have time over the winter to tear it down/replace etc. I really hoped I could rebuild it but the wife reminds me that her late husband used it heavily for years dragging out timber from our woodland, so it’s performed way beyond what was expected.
I’m anxious to call Tazewell as soon as they open back up and see what options they suggest. Even though for years I’ve usually done most projects myself, I’m a bit overwhelmed now, health-wise, aging, etc., and I have to admit it would be nice to have it done by a pro…(but I usually don’t like the more expensive tabs )

 

[5030]

Ever bother to adjust the overhead? Kohlers as well as Briggs and Scrap'em are very dependent on correct valve clearance because the compression release on both engines are actuated by an offset cam arrangement that acts on the intake valve initial clearance. Most owners never adjust the vale clearance and that equates to hard starting issues which owner blame on tother issues when, in fact, the vales are out of adjustment.

 

[5030]

Always keep in mind that these small engines (Kohler and Briggs) all have solid lifters and require adjustment (as spelled out in your owners manual, if you bother to read it)... Kawasaki as well.

 

[ponytug]

Oh for sure! LOL First, my curiosity is harping at me to dig in and see what has actually happened. Luckily, we don’t use it very much (I picked up a 1950 IH gas crawler/dozer several months ago that is FUN) so I have time over the winter to tear it down/replace etc. I really hoped I could rebuild it but the wife reminds me that her late husband used it heavily for years dragging out timber from our woodland, so it’s performed way beyond what was expected.
I’m anxious to call Tazewell as soon as they open back up and see what options they suggest. Even though for years I’ve usually done most projects myself, I’m a bit overwhelmed now, health-wise, aging, etc., and I have to admit it would be nice to have it done by a pro…(but I usually don’t like the more expensive tabs )

That 1950 IH sounds like fun! Where are you located? Hills? Mountains?

25HP diesels aren't exactly common, or cheap, but I think that it would make for an interesting tractor. But budgets, health, age, etc., do have a material impact on what is reasonable, in contrast to what might be possible...

All the best, Peter

 

[MossRoad]

The Kohler CH25 has hydraulic lifters and there is no valve adjustment. About all you can do is remove the valve cover, then check the nut that holds the rocker arms for damage/proper torque, etc.

 

[scotts562]

I have done a couple of engine swaps on PTs. It is pretty easy. Power trac can set you up with any parts you may need to adapt a new engine. Word of warning when installing the 90 degree oil drain elbow: do not overtighten or you will crack the block.

The following Kohler engine spec numbers will work. The HP ratings are per Kohler:
CH 730-3207 (23.5 hp) this one is in a 2422 with pumps on both sides of the engine
CH 730-3208 (23.5 hp)
CH 740-3363 (25 hp)
CH 730-3004 (23.5 hp) this is an old spec number but can still be used as a reference

Another spec number that may work, but I have not used is CH 750-3006 (30 hp)

When I called Kohler directly a few years ago, one of their service reps went through and identified a number of spec numbers that should work. He said they change some of the internals to get the different hp ratings, but the rest of the engine is a drop-in replacement.

Hope this helps