M18 carb

squatch · #1 11-07-2010, 10:50 PM

Well what I thought was a starter problem appears to be an M18 full of fuel. In the cylinders and crankcase! I parked at an angle on the hill out back for a few minutes to take my shadow pics and she has been acting up ever since. I guess for some reason the angle caused the carb float to stick open.

Anyway I think I have the Walbro carb on my 1872. I rebuilt it when I put the new engine in. I'm thinking of just replacing it with the Kohler carb. Is this a direct bolt in with the same linkage set up? Does anyone have a cub or Kohler part number for the Carb? Thanks in advance.

Light bulb moment as I was typing. I haven't gone any farther than checking the dipstick and finding thin smelly oil all the way up it yet. It just occurred to me that this is a fuel pump motor. Fairly new pump as well. now I'm thinking because of the heights of the tank, pump, carb. It's more likely the engine flooded through the (blown) pump instead of the carb. Any thoughts on this anyone. I'll probably tear into this tomorrow or Tues evening.

BCDSFCRET · #2 11-07-2010, 11:19 PM

Sir: parking your tractor on a hill has nothing to do with your carburator running over and filling up the cylinders and oil pan. Your needle and seat is leaking. The main cause of this is ethenol in the the gas. Ethenol eats the rubber needle and this causes the gas to leak into the cylinders.
To repair the problem: Install a fuel shut off valve on the fuel line as close to the carburator as you can place it. I do this so you can reach in and open or close the valve without removing the LH side panel.
Remember to drain and fill the engine with oil. Take out the spark plugs and place a old towel over the spark plug holes to catch the gas comming out of the cylinders. I would do this out in the open and not indoors.
Remember to either turn off the valve after use or before starting your tractor.
Good luck.

Matt G. · #3 11-08-2010, 12:02 AM

You can't buy a new Kohler adjustable carb. You will wind up with another walbro. You need a carb from a KT-17 series I.

Don't run it-- drain all the oil out, leave it drain for 2 or 3 days, pour a bit of oil down each cylinder. If you just replaced the fuel pump, I'd be more suspect of the carb; a leaky diaphragm will not fill the crankcase quite that fast.

squatch · #4 11-08-2010, 01:04 PM

Thanks folks, The pump was new and I rebuilt the carb when I installed the engine. I think I have another spare new pump. I'll get a rebuild kit for the carb. This all started when I stopped on the hill at a weird angle and this has been a few weeks ago and I haven't really run it since. Plenty of time for fuel to siphon into the engine slowly. I did start it before I had a clue what the prob was. I thought it was just a cold weather balk with the starter. It smoked like crazy but only ran it for a minute. I'll pick up a couple of filters and change the oil. then I'll do it again after running it to purge the oil lines to the filter. That's a pain. Draining oil from an 1872 because the drain is right over the tie rods. i've got a funky angled funnel I made from a rectangular juice bottle that helps a lot.

ol'George · #5 11-09-2010, 10:31 AM

FWIW, if it were me,
I'd carefully take the carb back apart, and see if the float was set correctly. and/or if anything prevented it from closing the needle valve. I don't remember if they have copper floats but if so, they can become brittle and develop a hole/crack. I have repaired many over the years.
If you damage a gasket, then you can buy another kit.

squatch · #6 11-10-2010, 12:48 AM

Thanks, I've rebuilt quite a few carbs myself over the years. This one has been running fine on the tractor for a while since rebuilt. I replaced the float and set the height when I rebuilt it. I've never had one flood the block before though. Small engine or automotive. I've heard of that happening.

I picked up a new rebuild kit today along with a couple of oil filters and ordered the bracket that connects the implement lift arm to the mower lift arm. Hopefully this will help keep me from breaking another rock shaft plowing.

Back to the carb. These float valves do indeed have a rubber tip and like stated above the dealer said they have been having fits with E10 eating up the tips and seals. I can't wait to see what's inside. Haven't had time yet this week to get to it.

Just for grins and giggles I priced a new carb. Dealer laughed and said probably $350 and he was serious. It was only $240. Next time I'll just put a Weber or Holley on it and save some money! ha ha.

Matt G. · #7 11-10-2010, 01:14 AM

I imagine you may continue having this problem. The seat is not replaceable in the Walbro, as you've probably discovered, and if it's worn, a new needle won't fix the problem for very long. The best solution in my opinion is to remove that POS Walbro and put on a rebuilt adjustable carb from a KT-17. That carb is completely rebuildable, and you'll be able to adjust it so that the engine will idle nicely. Very few of the twins with the Walbro will idle right.

squatch · #8 11-10-2010, 09:14 AM

Quote:

Originally Posted by Matt G.

I imagine you may continue having this problem. The seat is not replaceable in the Walbro, as you've probably discovered, and if it's worn, a new needle won't fix the problem for very long. The best solution in my opinion is to remove that POS Walbro and put on a rebuilt adjustable carb from a KT-17. That carb is completely rebuildable, and you'll be able to adjust it so that the engine will idle nicely. Very few of the twins with the Walbro will idle right.

Got a spare one? Mine until a couple of weeks ago ran and idled fine. I'm thinking part of the problem is that the engine sat for a while this spring and summer during the "Rat Rod" rebuild. It was running well so I didn't touch a thing on the engine other than new fuel, air + oil filters and plugs. That and a wipedown when I reinstalled it. Funny after I put a new muffler on it shortly before the rebuild the backfire issue when hot went away as well.

I'll hit it hard this weekend and hopefully finish painting the Cab as well. Weather is suppossed to be nice. I don't expect that to last long.

pulse301 · #9 11-10-2010, 09:34 AM

I've been lucky that both my cubs so far have had the original Carter carburetors on them, even though i had no idea to check for that. Are the Walbro carbs on the M18 really completely unadjustable? Or are the adjusting screws just smooth where you could cut a slot in them to make them adjustable? Anyone have a picture of an unadjustable one so I know what watch out for when I end up feeding my addiction to buying my next unneeded, but much loved tractor? I had to buy a special tool off of ebay (only place I could find it, but was only $6) to adjust my crappy weedeater trimmer.

Matt G. · #10 11-10-2010, 09:55 AM

There are two versions...one claims to be adjustable and has adjustment screws, but they don't really do anything. The other has none. It'll say "Walbro" on the side, and there is no large main jet needle on the top like on the Kohler carbs.