Fitting a K301 carburetor to a M12

[Maxwell-8 4,277]

I own my Raider 10 with a resto-mod Kohler M12. But I have been fighting with the tranny and carburetor. 

After been looking for a Kohler M12 carburetor, I found this NOS Walbro K301 carburetor. Didn't want a Chinese one.

I thought It would just bolt up, but that was not the case. Their are some differences. 1. Bolt holes 2. choke lever 3. PCV breather.

 

 

It will bolt on to the engine with no problem, but being able to run the M12 air-filter, that takes some modifications 

 

In this picture you van see the choke-linkage is in the way. the K-series airfilter housing has an offset for this. The M12 airfilter housing is dished

 

As you can see, It doesn't want to 'touch' the carburetor. 

An option could be removing the choke, but I prefer having a choke, and switching out the choke arm wasn't possible.

 

So we are going to make a spacer so the airfilter housing from the M12 and the choke can both be used.

 

so I start things off using this big plastic board of 15mm or 0.60 inches thick, I believe this is the minimum that was needed.

 

 

Used the OLD carburetor to see the outline of the spacer, it is very important to use the old one or 2 holes are not going to be sealed, and unfiltered air can enter the engine.

For the holes, You have to use the NEW carburetor

 

 

 

Insured It would also fit the dished air filter holder of the M12

 

 

Also used a holes-saw that was exactly the same diameter as the inside of the carb to cut out an opening in the spacer.

 

The bolt keeping the airfilter-holder on will need to be upgraded to longer ones. Make sure they are not to long as this may clamp choke lever stuck.  (ask me how I know )

 

 

The M12 airfilter only has  the bottom hole and the two bottom ones. So I had to drill two extra holes so the K-301 carb will bolt up, as you can see by the gasket 

 

 

So now it is time making or buying some gaskets: You know will need two instead of one. So I had an OEM one, an decided to make the other from left overs from a WH tranny gasket.

 

I used @Achto trick with the leather punches. They sure make it an ease to cut out the prefect holes.

 

 

Next problem is that the PVC breather hose will be too short to fit, so this will have to be lengthened. I used a this plastic hose connector

 

. 

 

You could also use the exit at the K carb instead of the exit on the M12 filter housing. I didn't go for that option.  As sealing off the carb exit will be easier.

 

 

 

I still did had to cut off the horizontal tab on the choke lever.

 

 

And we are now ready to bolt everything up.

 

 

 

View on the choke lever: 

 

Choke OFF:

 

 

Choke ON:

 

 

And voila the filter and filter housing  of the M12 is now on the K-series carb which is now on a M12..

 

Now the plastic cover has a final minor issue. 

The tab that goes into the the front engine cover, that keeps the plastic cover from turning is now too short. 

So I used a small metal strip to make up for it.

 

A question: Could you keep the plastic cover out, or is it important for keeping the airfilter clean?  Since this cover is now sticking out more, I barely clears the hood. 

 

Edited November 12, 2021 by Maxwell-8

[Achto 27,601]

20 minutes ago, Maxwell-8 said:

Could you keep the plastic cover out, or is it important for keeping the airfilter clean?  Since this cover is now sticking out more, I barely clears the hood. 

 

Nice work!!

 

You could go with out the plastic cover, I would slide a foam pre filter over the air filter if you went this route.

Could also look for a round air filter cover from a K model engine.

 

[Maxwell-8 4,277]

21 minutes ago, Achto said:

 

Nice work!!

 

You could go with out the plastic cover, I would slide a foam pre filter over the air filter if you went this route.

Could also look for a round air filter cover from a K model engine.

 

Along with the carb, I picked ups some more NOS stuff, like two of those prefilters! thanks

 

Edited November 12, 2021 by Maxwell-8

[kpinnc 12,087]

You might be able to swap the choke butterfly shaft with the old carb. Just don't lose the detent BB when you remove it.

 

You'll likely need new brass screws for the butterfly plate. They break when removing them typically. Loctite is your friend when you reinstall new ones...

Edited November 16, 2021 by kpinnc

[Maxwell-8 4,277]

4 hours ago, kpinnc said:

You might be able to swap the choke butterfly shaft with the old carb. Just don't lose the detent BB when you remove it.

 

You'll likely need new brass screws for the butterfly plate. They break when removing them typically. Loctite is your friend when you reinstall new ones...

tried that first, diameter of the shaft was different I believe, has already been awhile..

 

Screws luckily didn't break. 

 

[peter lena 8,634]

@Maxwell-8  add a fuel check valve , just before your fuel pump , in a vertical position ,https://www.amazon.com/Joywayus-Return-Check-Petrol-Diesel/dp/B07MMRNHP7 , easy to install , always have a fuel charge waiting to go , have them on my 3 horses , pete

[Maxwell-8 4,277]

Just now, peter lena said:

@Maxwell-8  add a fuel check valve , just before your fuel pump , in a vertical position ,https://www.amazon.com/Joywayus-Return-Check-Petrol-Diesel/dp/B07MMRNHP7 , easy to install , always have a fuel charge waiting to go , have them on my 3 horses , pete

That is a great idea! Didn't taught about that. That will decrease crank time and if not, won't hurt anything.

[kpinnc 12,087]

7 hours ago, Maxwell-8 said:

Screws luckily didn't break. 

 

You should have bought a lottery ticket that day- the force was with you for sure! 

[Maxwell-8 4,277]

2 hours ago, kpinnc said:

 

You should have bought a lottery ticket that day- the force was with you for sure! 

Have a set of screwdrivers for electric stuff, their are way more precise, and then a very gentle twist while putting enough downwards pressure on it. 

Thanks for sharing cause I didn't know they broke fast.