1974 John Deere 300 with a 292 Kohler
- Thread starter H33Bzz
- Start date
will probably be the best thing you do for that motor, I don't have any specs to give you but have done a few Mikuni swaps in the past. I did them by looking at a comparatively sized motor in a sled that was already equipped with a Mikuni carb and gave me an idea where to start with jetting so that the trial and error stage wasn't so involved because it will take a little time to get it dialed in. Its been a while since I have done this but I am thinking a 34 - 36mm Mikuni carb would be the one to go with, and a single outlet fuel pump. Always start rich on the jetting to prevent any engine damage while trying to figure out what's best, because it can occur quickly and you wont know it until its too late. Maybe reaching out to skiroule or he may see your post and chime in on this as well.
Last edited:
Just want to add one more thing and maybe you already know this but don't over think the swap with carburetor set up, the jetting set up for the pilot (idle fuel) circuit should be good with what the carb comes with and is adjustable. The jet needle and needle jet set up that the carb comes with should also be sufficient, the only battle you will have will be the main jet and as I said I would look at another sled with that or around that size of engine equipped with a Mikuni carb to get a general starting point and I would start a little rich and work your way backwards...SLOWLY And you will be purchasing an intake boot that will likely be aftermarket, make sure you have a good seal against manifold before you start playing with jetting or adjustments or you may end up running in circles with the process.
skiroule
Well-known member
Euphoric1 did a great job of covering the details so there’s not a lot I can add.
We did do a Mikuni conversion on my brother’s 72 John Deere 340 (CCW) I know it’s not necessary apples to apples with the smaller Kohler but it might give you some things for reference.
We used a 34 mm Mikuni. One issue we had was finding a boot that would fit the carb and the intake bolt spacing. I ended up filing the bolt holes slightly on the one we used (it doesn’t affect the seal if the O-ring is good). You might be able to find one that doesn’t require modification.
We finally settled on a 30 pilot and 330 main. It’s a little fat but he previously burned it down with the Walbro so we wanted to go conservative. I think the 30 would be fine for your motor and you could start with a 330 or 320 and see how it runs.
The John Deere throttle block will work with the Mikuni cable but it seems like I might have had to tweak it a little but I can’t remember exactly how. The Mikuni has a long pull so make sure the cable is adjusted on the carb to close the slide all the way at idle.
Hope this helps.
We did do a Mikuni conversion on my brother’s 72 John Deere 340 (CCW) I know it’s not necessary apples to apples with the smaller Kohler but it might give you some things for reference.
We used a 34 mm Mikuni. One issue we had was finding a boot that would fit the carb and the intake bolt spacing. I ended up filing the bolt holes slightly on the one we used (it doesn’t affect the seal if the O-ring is good). You might be able to find one that doesn’t require modification.
We finally settled on a 30 pilot and 330 main. It’s a little fat but he previously burned it down with the Walbro so we wanted to go conservative. I think the 30 would be fine for your motor and you could start with a 330 or 320 and see how it runs.
The John Deere throttle block will work with the Mikuni cable but it seems like I might have had to tweak it a little but I can’t remember exactly how. The Mikuni has a long pull so make sure the cable is adjusted on the carb to close the slide all the way at idle.
Hope this helps.