B-80 Repower

[Steiner430! 0]

 

I would like to repower my B80 with a 12 HP Kohler engine. Can this be done? What modifications do I need to make if it can be done.

[kpinnc 16,094]

If the old and new engine have the same ignition type, and the 12HP has the correct oil pan, the swap itself is easy. 

 

You will likely need a new drive pulley (1.125 ID) and the associated PTO bearing race. 

 

If the 12hp has any oil pan other than what is in the pic below, you'll have some degree of fabrication to do.

 

Even if it is of this type, if it didn't come from a Wheel Horse you'll have to drill and tap the PTO side bolt holes or use J bolts. 

 

Many of us have repowered these old tractors so it isn't impossible no matter what fits if you want to swap it. Just makes it easier if you start with the right stuff. 

 

 

Edited 20 hours ago by kpinnc

[wallfish 18,733]

A K301 12hp engine should bolt right up. (From a Wheel Horse) WH spec engines have threaded holes in the bottom of the oil pan to bolt to the frame but simple J bolts can be used if the engine isn't a WH spec engine. The same size shaft and you can swap all your 8 hp stuff right to it. Find one with a 1" shaft

Do you already have an engine?

[ri702bill 10,452]

7 hours ago, kpinnc said:

If the old and new engine have the same ignition type

 The B80 had a battery ignition, if you are planning on using a Magnum engine, that has magneto ignition. Doing so requires the correct mag style ignition switch and a bit of re-wiring...

[Racinbob 12,368]

The others have mentioned the potential changes depending on what engine you get for it. If it's a K-Series it might even have the tapped holes in the bottom of the oil pan already. I purchased a new 1976 B-80. Here it is in it's original form.

 

A short time later I picked up a new K-341 from WW Grainger when Kohler phased out the K-Series. In 76 and 77 the B and C series were identical as far as frame, transmission, etc. with just a few differences to economize the B's and of course the engine. Going from a K-181 to a K-341 was pretty cut and dry. The new engine did have the mounting holes drilled and tapped. The bearing race in the PTO had to be changed from a 1" ID to a 1.125". The OD is the same on both. The upper PTO bracket is a little different but the small block bracket was easily modified to match the mounting holes on the big block. Going from K to K made it really simple. In my case perhaps the biggest issue was the starter. The welded on bracket on the new engine was what I called a low mount. The mounting holes were above the starter body. The original spec engine had a high mount, the holes were below the starter. This created a little interference with the battery but it was easily handled. It ran like this for 40+ years.

 

 

Recently, I decided to convert it back to a B-80. It is now dedicated to snow blade all year. The conversion back actually brought back some memories of the original swap. Search for Reborn B80 here and you'll find a thread I did on it. There might be some things in that to help you. 

 

As she sits now. 

 

Edited 12 hours ago by Racinbob

[midpack 1,071]

59 minutes ago, ri702bill said:

 The B80 had a battery ignition, if you are planning on using a Magnum engine, that has magneto ignition. Doing so requires the correct mag style ignition switch and a bit of re-wiring...

I replaced a Kohler with a Magnum and used the original ignition switch and wiring. I had to add a relay, I found the info on how to do the modification on this site.

Much easier than changing the wiring and switch. I did one like that too.

[953 nut 62,812]

10 hours ago, Steiner430! said:

Can this be done?

Welcome to the site where anything is possible if you are willing to do the work. Lots of good people here that are willing to help, Answer the questions above and we will get you started in the right direction,

 

[ri702bill 10,452]

3 hours ago, midpack said:

and used the original ignition switch and wiring. I had to add a relay, I found the info on how to do the modification on this site.

I take it that the secondary circuit of the relay was the engine kill ground wire??

[Goldnboy 1,064]

I installed a Magnum in and the wiring is not all that difficult except the that you need to know the correct wire from the engine "M" needs connected to a different key switch for a magnum engine. You may need to enlarge the hole on the dash to accommodate the key switch as that hole varies by mfg. Plus you need to run ground to key switch. 

Edited 8 hours ago by Goldnboy

[ri702bill 10,452]

As she sits now.... dressed for the Winter Dance!

[ri702bill 10,452]

6 hours ago, midpack said:

I had to add a relay, I found the info on how to do the modification on this site.

Do you still have that info?? Curious to see the circuitry, particularly to understand the duty cycle. One that has a 100% duty cycle is always on, unlike a starter solenoid. Always energized can shorten its life...