OK, decision time: 28 or 35

[KMA]

OK, that might be a bit much to make that work. Back to the Kawasaki FD791D horizontal liquid cooled, DFI 26 HP engine. This would require an additional 4" in the tub over the existing Robin 25. At $2200, it isn't much more expensive that the air cooled twins.

Kawasaki Engine Model FD791D-S01 - On Sale At Tulsa Engine Warehouse

View attachment 433434View attachment 433437

I think that cutting the back plate off the tub and welding a 4" extension would work. You could continue the natural slope up of that back section of the tub to avoid giving ground clearance problems. I think with a bit of thought this could be done elegantly. I think if I was re-engining that I would start playing around with solidworks to see if I could fit it all in.

This was the engine I was looking at a while back. I didn't spend much time on it, but do you think the radiator connections could be extended such that it could be mounted on the back of the tub (with a protective shroud)? Maybe the rear-facing side of the cover could be removed so that it would rotate right over it when opened? I was thinking the bulk of the existing tub could be left as-is and the only major fab would be the shroud. That being said, I didn't actually look at measures, etc...

 

[Marks481]

Maybe the rear-facing side of the cover could be removed so that it would rotate right over it when opened?

That might be a good approach. It looks like the radiator makes up most of that extra 4" that would be required. If so, that would be easier than welding 1/4" plate extension onto the back of the tub.

The version of the Kawasaki 791D that mounts in a Toro has a stub shaft on the flywheel side. So you could mount the engine backwards, with the muffler hanging out the back (which seems to be a better place for it than hanging over the hydraulic pumps in the middle of the tub). The radiator could be mounted at the front (or middle) of the tub, drawing air into the tub from behind the drivers seat. Establishing a natural air flow like that would help cool the whole engine compartment better. This might require some innovative reworking of the gas tank to allow a path for airflow to the radiator.

The Toro part numbers for the stub shaft I came up with was 110-6249 and 112-2335 (both required). Not sure this is specifically for the Kawasaki.
Toro Z580 parts

 

[joshlee]

Oh really? I didn't know that. Is there a special reason why?

Since we're supposed to run our gas engine Power Tracs at full throttle anyway, would it really matter?

 

[stray]

I just bought another pt. A 428 fi. First time I used it; it got hot and would not run. I assume it was vapor locked. It didn't surprise me. I just went and got the old 422 and finished the job. These engines don't like cold and they don't like it hot. So I have to fix the design problems with an oil tank heater $150. Then I will add a blower to force air in to the tub for hot weather. That is just the way it is. And I was not surprised when this happened. I just have to do the design work Power Trac should include if their engine does these things.
I will eventually put an engine in my 422 but I probably won稚 be a robin engine. Moss seems to have good luck with his engine starting in cold and not quitting when hot. Isn稚 it a Kohler.

PS I realy still like my Power tracs. and i am happy with the 428. just need to do these things to get it right. it's fixable.

 

[marrt]

Well, it isn't looking to promising for the 35. The 35 uses (I think) an SAE B engine mount configuration. This has a pilot flange of 5.75". My old 25 has a pilot flange of 6.43". This is probably some type of metric standard. It's a lot easier to take metal off than put it on. I may call PT and see if they have a motor mount that will work. However, it's now looking like the 28 will be the easiest fix.

Interestingly, my shaft is 1 7/16. Further, it doesn't use a lovejoy connection. It uses some type of geared arrangement connected by a sleeve. Pretty neat set up.

 

[joshlee]

So, how long do these wheel motors usually last on these PTs? Just curious.

Frank,

If I remember right, Gravy said the 35 is only about half an inch longer. I assume that doesn't include the debris shield. Apparently, the 35 has some type of rotating debris shield that keeps junk out of the fan. Grady also mentioned the engine was actually a bit narrower than the 25 which could help a lot with cooling.

I was leaning toward the 28 but, after the responses here, I may go for the 35. It's not much more expensive and it's not a Subaru (it's a re-badged Generac). Whatever I do, I'll try to document it with lots of pictures. I already have new wheel motors on the way and a suspension seat in the garage along with some new LED lights. So, might as well do everything at once.

Tom

 

[woodlandfarms]

So, how long do these wheel motors usually last on these PTs? Just curious.

Like any part on any machine, 3 weeks or 30 years. JJ will probably know, but I bet the life expectancy is around 3000 to 5000 hours. But there are so many variables.

 

[Marks481]

My old 25 has a pilot flange of 6.43".

OK, my google-fu is weak; I cannot find an engine flange size that corresponds to 6.43" (or 163 mm). Closest I can see is 160 mm (6.30").

More important question: what is the flange dimensions for the hydraulic pump. Assuming that is standard size, you should be able to buy pump-engine mount that will fits between the engine and the pump. That would free you up to buy the engine you really need (35 hp) vs settling for an engine that fits the current mount.

You probably can find the replacement mount for less than $100).

 

[joshlee]

Thanks. Thats what I sort of figured. As far as the life of the Subaru EH72 goes, hopefully it will last a good while after installing the fan and Subaru header/muffler.

 

[MuncyBob]

Is your side fan pushing or pulling air?