It is covered in the free service manual from kohler avail in out resources section, on page 3 near the bottom.:beerchug:

Im at wits end with this thing. Just started mowing again and not even 50 feet it starts falling flat again and started surging. Pull the choke all the way out it runs fine. It is just better to junk the walboro carb and buy a new one off the net?

I recently got my butt kicked by one of the non-adjustable carbs on a M18, I replaced it with a used adjustable jet style off a blown KT17 I have. The only thing I can figure is I did not pull the welch plugs out and there is still crap in there, although in my case it is possible someone else messed something up internally because the carb had been recently "monkeyed with" trying to solve a poor running issue. Not saying you need a new carb, just that I had a couple folks tell me they have no luck rebuilding the ones without an adjustable jet.
Best of luck.

Im looking online at some but im tired of messing with it.

Do you have a fuel filter on this thing?? You said you did in post #1, but what kind is it? Is it a filter, or a screen?


I do not understand why people have so much trouble cleaning out carbs. I just don't get it. I've had people bring me carbs off tractors out of junk yards to rebuild for them that literally were full of rust. Nearly solid full. Like all the passages full of rust and packed full of crap... and I didn't have any issues rebuilding it and giving it back to them and it worked on the first try. What can we tell you that will make it easier for you (and all the others that struggle with this process)? Would a video help? There are only so many passages on this tiny little carb, and they all have to be completely free of dirt. COMPLETELY. I spray brake cleaner into each of them and watch for it to spray out all the ports. You can't see compressed air, but you can see brake cleaner spurting out. (WEAR SAFETY GLASSES!!! Brake cleaner in the eye hurts like hell!!!) I just don't know what to tell you that will help. You don't have it clean yet. You need to flush the system again. You probably should buy another fuel filter, just to be sure that it's good.

Sure. Buy a new carb. Easier that way. BUT,,,,,, if you have junk in the fuel system, or a bad filter, or a bad pump..... it's just going to do it to that one too.

You are sure you have the direction for the filter going the right way correct? Is it allowing flow enough to feed the Mag 18??? Not to small or restrictive?

I had an issue near this and a new pump fixed it.... make sure your float and seat are set properly as this will alter the amount of fuel in the bowl...

Governor adjustment is easy for the surging issue once you get it running under load.

J Mechs comments above are spot on for the carb cleaning aspect....

Good point. Those mags drink fuel like there is a hole in the tank. Every part of the fuel delivery system needs to be working.

Never figured out if mine is still clogged internally or if the last guy working on it screwed something up trying to clean it out by poking drills and wires in places he shouldn't have. I mean after all, he glued the fuel bowl back on. :bash2: Anyway, I'll probably try it again one day--soak it out again, but remove the welch plugs this time. I do have a KT17 that needs a cleaner/better carb.:biggrin2: FWIW, I replaced all my lines, washed the tank, and replaced the pump.

If you pull the choke and it runs better, it's clogged up. If it is overfueling, then he may have gotten a hole too big. FWIW, I prefer the adjustable unit's also. But I also have lots of carbs sitting around, so all of mine are adjustable. May have been a regional thing too.... I don't know that I've ever had a Cub that didn't have an adjustable carb. Maybe I am just lucky. I've not ever needed to remove a welch plug on these little carbs. Not saying that isn't a good idea if you can't get it clean though.

So, not trying to derail the thread from the OP, honest. We couldn't make mine run correctly even with the choke on. Really are leaning toward something modified/damaged during prior repairs.

So regarding adjustable carbs, does anyone know a source of used ones--as in what engine? My M18 in my 1811 had a fixed jet. I have a parts 682 with 2 blown engines--the first was a series 1 KT17, it had a fixed jet. The replacement series 2 had the adjustable that I robbed for the M18. I have no idea what carb is original to any of the engines, other than the one on the series 1--that engine blew at 200 hrs.