Kit to make 422 into 428

bullitt · Feb 15, 2003

It appears I will be installing a 27 or 28 hp Koher into the 422 as posted ealier.

I am considering documenting the conversion and making it into a kit, using largely commercial parts at about $2k.

However, there is no point in doing this is there is not a market for it that will cover my costs and provide a small profit. To support that, I need some idea what the market for such a kit woud look like to help in negotiation with potential suppliers.

If this works out, I have some other ideas that could be of use to PT owners that might follow.

If you think you would be seriously intersted in the 422 to 428 conversion, please send me a private message so I can determine if it potential market is worth the investment of time.

thanks
bullitt

bullitt · Feb 15, 2003

It seemed like a good idea at the time, but it is impractical.

The Robin crankshaft is not centered side to side and the crankshaft is .87" lower than the kohler, therefore extensive modification to the cradle is required, meaning its reuse is impractical.

That means the conversion is not practical independant of parts from Tazewell, and so dies the dream of a cheap upgrade to more power.

I will still be putting the largest engine in that the Kohler cradle I will have to buy will support, and will provide that info to anyone who is interested.

bullitt

bubenberg · Feb 15, 2003

if you ever try the conversion to a diesel eng. i would be interested. one engine that comes to mind is the Cummins diesel eng. i think it was last year we toyed around with this conversion on this site (about 18 hp)

looking forward to hear from you, keep the thinking juices going. /forums/images/graemlins/smile.gif

MossRoad · Feb 15, 2003

Maybe one of these? /forums/images/graemlins/laugh.gif

bubenberg · Feb 15, 2003

what do you think? have you checked out the dimension Mr. M.R.? reads quite like what i would like, the "green beasty tank" will outlast the Kohler eng. by many years even under my more intense use and just like you i LIKE my pt425 and am going to give it(really me ) more toys to play with. My goal is that the 425 is going to make me the money to get a 1845. /forums/images/graemlins/blush.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/tongue.gif /forums/images/graemlins/wink.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/grin.gif

hans

MossRoad · Feb 15, 2003

No, I haven't checked it out... I was just enticing everyone else to check it out for me /forums/images/graemlins/grin.gif

bullitt · Feb 16, 2003

As always, the devil is in the details.

The limiting dimension in my view is length. This is the reason I ruled out the 28 hp Kohler engine yesterday. It is possible to make it fit, but you will not be able to remove the rear pump without pulling the engine and disconnecting the hydraulic hoses because it is an inch longer. This is a bigger problem to me than the difference in hp and torque.

At this point, unless a new possibility opens up, it looks like will will be putting in the 25 hp kohler that is in the 425. Once I get that model numbers, I will get the drawings and check out some of the more exotic angines.

bullit

duane · Feb 16, 2003

Bullit,

Ed went through a incline climbing problem with his PT425 while powering his 60" mower. In his case, it was'nt a motor horsepower issue, but a system relief lifting in his transmission pump due to the wheel torque required. The only reason I mention this is I would not want to see you go through all this effort and expense, to find out that you are limited by the hydraulic transmission. Another solution to more wheel torque (incline climbing ability) is to go with smaller diameter tires, or different wheel motors. I'm guessing that new wheels and tires would be about $400 while new wheel motors $700 - $1000. In either case, you would lose travel speed on the top. This might not be acceptable to you. No matter what option you pick, keep up the ingenuity and vision. Let us know how we can help.

Duane

Pacesetter300 · Feb 16, 2003

Another possibility that hasn't been mentioned. I see Northern Tools has 24HP V-twin Honda GC series engines for about $1200. I would say it's worth looking into. Out of curiosity, I looked at the specs on the Robin. The net HP is 18 and they only promise 85% of that, so it could be as low as 15.3 On top of that you're off approx 5% for every 1/4 mi in altitude. Heck, someone in Denver could have about 12 1/2 Hp net, almost 10 less than advertised!
Pacesetter

MossRoad · Feb 16, 2003

( Once I get that model numbers )

Ok, Ok /forums/images/graemlins/laugh.gif

I was busy yesterday, as my 10 year old was testing for her green belt in Karate... she passed with flying colors /forums/images/graemlins/smile.gif

Here's the numbers from my PT425 Kohler:

MODEL CH25S
SPEC # 68500
FAMILY YKHX5.7252GC

Hope this helps.

FYI. It was 5 degrees in the shed this morning and the ink froze in the pen /forums/images/graemlins/shocked.gif

And I'm supposed to go inner tubing or cross country skiing today..... BRRrrrr. /forums/images/graemlins/tongue.gif

bullitt · Feb 16, 2003

Moss Road and duane,

I did not mean that last post as harrassment. If it was not for the Moss Road web site, I would not have this rather amazing machine. Thanks for the info. It will save me about $1800 to buy the engine myself.

I plan to contact Kohler and get the dimensions so I can judge what (if any) modifications are required to the Kohler engine cradle for whatever engine I end up with.

The report from duane on the 425 with the 60" mower is reassuring that with the 25 hp Kohler I will get the performance I expect.

My main frustration now is I can't lift the reliefs with the Robin engine, instead I lug or stall the engine. If I back off the treadle so that does not happen, I have to back off so far that the tractor does not climb. I suspect the variable volume hydraulic pump becomes so inefficient at close to the neutral position that the output pressure drops, and I end up "hung up" on the hill.

If I have an engine that can lift the reliefs, I will be satisfied I am getting all the function I can out of the tractor (I am not yet ready to adjust the relief valves). Right now I am concerned that with the Robin engine I will not be able to drag or push items up a 15 -20% slope, and that I will not be able to cut uphill, even with my 48 inch deck. My land requries that capability.

Thanks for the help and ideas
bullitt

MossRoad · Feb 16, 2003

( I did not mean that last post as harrassment. )

None taken /forums/images/graemlins/laugh.gif

FYI, I've never had the reliefs open on my PT425 except for the time I forgot to hook up the hoses to the main PTO and turned it on. I've lost traction and spun the tires on steep slopes, but the engine and hydraulics never gave up. I have turfs, and have wondered if I had bar tread if I would have kept going up the hill or stalled/releifed it.

Anonymous Poster · Feb 16, 2003

Maybe you could consider making a plate to go across the rear of the 425 in place of the current rear of the frame
make it from heavy steel and removable with four bolts
then you could get easily get to the pump.
- ie if you need more room for the 28 hp model

Anonymous Poster · Feb 16, 2003

Oh just to chime in - I am happy with the power output of the Kohler 25hp - there are many posts talking about the problem I was experiencing - and as Duane mentioned - it was not the engine - I pushed my 60 inch deck up a 21 degree incline
and what I experienced was wheel motor limits - not engine or PTO limits - I think it was wheel motor limit as opposed to the pump because the pump used is fairly powerful. (but it could have been reliefs)

Also - despite it having some difficulty (full throttle required)- it still cut the slope twice a week - i just felt that I was forcing the tractor to do something beyond it's capability - (heat also makes it worse)

bullitt · Feb 16, 2003

Keep the ideas coming. I am still not sure how extreme the modifcation may end up.

bullitt

Anonymous Poster · Feb 17, 2003

( That means the conversion is not practical independant of parts from Tazewell, and so dies the dream of a cheap upgrade to more power.)

What other parts might you need beside the cradle...Are the couplings reusable? What does PT want for that Kohler cradle.

Haven't looked at mine yet real close, so I'm wondering if a local machine shop could take off additional radius of .87" of coupling access and relocate pump mount holes up .87"?

bryce · Feb 17, 2003

Does anyone know where I can get a Duetz diesel for a PT? I am trying to find a better price than PT. charges. Robert /forums/images/graemlins/crazy.gif /forums/images/graemlins/shocked.gif

Anonymous Poster · Feb 17, 2003

If you go to their website - they have a dealer locator - I found a great dealer here in CT - I just wanted to touch base with them since I now have one

-edm

bullitt · Feb 17, 2003

bkmar,

It is all still under evaluation. I need to make some drawings and compare the various dimensional differences. Then I need to evaluate the hassle factor.

The only certainty right now is the engine will be >25 hp.

bullitt

marrt · Feb 17, 2003

I have been casually investigating the possibility of swapping the Kohler 25HP for a Diesel engine. The Briggs and Stratton 26.5HP Diesel (made by Daihatsu) is one possibility. The engine itself is supposed to be one of the most compact Diesels you can buy and measures 19.76”H x 17.43” W x 15.59” L without the fan and radiator. Since this is a water-cooled Diesel, one would have to find a place for the radiator. I don’t know the size of the radiator. This engine has a fairly larger alternator so you could use an electric fan for cooling the radiator (and, therefore, mount the radiator wherever its convenient). The Kubota D1105 is a great little engine. I think it’s the engine that’s used in the BX. I don’t know the dimensions but, judging from the size of the BX, I’d say it would fit. Also, Lombardi makes a number of air cooled diesels. Then of course there is the Deutz 1011F oil cooled series.

At a given HP rating, Diesels tend to have more torque, last longer, and use less fuel. Therefore, there are a number of folks, like myself, who would like to see a Diesel conversion for the PT400 series.