Allis WD - MS Carb Issues

Heyall,

I posted a few weeks back when I was trying to get my new to me WD running. Since then it's undergone paint and working out gremlins.

Now I am pulling out what's left of my hair due to a carb issue.

I cleaned and rebuilt the Marvel Schebler carb. I was having issues with the fuel bowl overflowing, which ended up being a leak around the base of the float needle seat. It ran fine, but leaked when parked. I mowed 5 acres of pasture, did a bunch of joy rides, that kind of thing without any issue otherwise.

Yesterday I took the carb apart, and torqued the seat down snug and was able to get it to stop leaking. Also re-checked for crud, and everything is clean as can be. I reset the float level, and now the carb isn't dripping.
So I jumped on the tractor and drove it half mile down the road to my dad's farm, picked up my snow blower, drove home, and parked.

Today, so far we have a foot and a half of snow, and I decided to move some of it. First thing when the tractor started, it was barking and popping from the exhaust. Adding choke didn't help. I backed it out and let it idle for 10 minutes while I did other things. Trying again to move snow with it at full temp, and it would start to die within 30 seconds of starting to work, bark, pop, done. Wait for 30 seconds, and it starts right up again.

Back in the shop, I put the clear fuel line on the carb bowl drain and checked the float level. With the engine off the height is perfect. At an idle, it drops to about the 2/3 mark, and as soon as I move it to half throttle, it drops right to the bottom and starts running lean. Whacked the carb a few times in case the floats were hung up, without success.

I ran the drain line into a cup, and it is running full flow through the tube.

Anything else to try? Certainly seems like a supply issue, even though the supply seems to check out. And it was perfect yesterday! But using the clear line, I can prove that the bowl level is dropping too low. The only difference between yesterday and today, is that today they are calling for 3 feet of snow, and I need the tractor!

Thanks all.

It always bothers me when I hear someone adjusted the float level. I can honestly say in 45 years of working on tractor carbs that I can count on one hand how many I have ever changed from what they were when I took the carb apart. The ones I did change were obviously done by someone else who didn't really know what they were doing. When you hold the carbs top upside down, the float should be level. That's it. I think your float is adjusted wrong OR it is dragging on the sides of the bowl from being tweaked. Think about it. If someone brought me a carb that had been fine for maybe 5 to 10 years and then it started running over when it sat, the automatic repair was a new needle and seat valve and a bowl gasket. I sure as he&& didn't change the float height, because it had been fine for years before.

(quoted from post at 10:12:12 11/18/22) It always bothers me when I hear someone adjusted the float level. I can honestly say in 45 years of working on tractor carbs that I can count on one hand how many I have ever changed from what they were when I took the carb apart. The ones I did change were obviously done by someone else who didn't really know what they were doing. When you hold the carbs top upside down, the float should be level. That's it. I think your float is adjusted wrong OR it is dragging on the sides of the bowl from being tweaked. Think about it. If someone brought me a carb that had been fine for maybe 5 to 10 years and then it started running over when it sat, the automatic repair was a new needle and seat valve and a bowl gasket. I sure as he&& didn't change the float height, because it had been fine for years before.

Click to expand...

Thanks for the reply. Since I had an issue with the bowl overflowing (valve seat was slightly loose) I lowered the float height slightly to see if it would improve. Once I found the cause of the leak, I simply adjusted it back to level. I know someone has been in this carb before me, and I have only owned it for 3 weeks, and I had never seen it run. So starting from scratch.
I've been cleaning and rebuilding these carbs for years, and although I don't typically make adjustments to the floats, it is something I will always check.

Floats rubbing makes sense if they aren't able to drop far enough down, but if that were the case, I'd expect to see less than adequate flow from the drain.

It's got me puzzled, and I am reluctant to pull the carb off yet again. But it might just come to that.

Thanks.

.

Some carbs have a fine mesh screen at the elbow of the line connection to the carb. That might be full and starving fuel.

Or a sticking needle, is there a spring tied to the needle and float?

.

Hi,

There is no mesh screen in my elbow. It has been thoroughly cleaned out to confirm.
The float needle does have the clip to pull it down. I thought maybe about adjusting the drop on the floats, but as DrAllis said, if it was working fine, then don't change it. Yesterday I had no problems at all.

Thanks.

Just double checking my logic: Using the clear tube technique to measure fuel bowl height, the drain is right beside the pickup for the main jet, right? So perhaps when the engine is running, it is simply sucking the fuel away from the tube, making it look like the bowl height has dropped.

In theory, the engine should run for a minutes with the fuel shut off entirely. So it really shouldn't drop instantaneously when I rev up. Makes me wonder if I am chasing a red herring.

I should double check everything else before I jump to the carb...

Float MAY not be dropping enough due to a mis-adjusted float drop stop (IF it has one) or by a bent float contacting the float bowl before it drops adequately.

Or, needle and seat from The Land of Almost Right may not be made correctly to allow an adequate flow of fuel.

Well, I am a bit embarrassed. Somewhere on the web, I read something that said, "when you are 100% sure you have a fuel problem, then you have an electrical issue". Or something like that.

I removed the carb, again, and found nothing out of the ordinary.
Removed the spark plugs and found them a bit sooty looking.
Removed dizzy cap to discover that my points are nearly non-existent. They were set to spec previously, but it appears that the lobe that rides on the shaft is worn nearly smooth, and the one side of the breaker contacts is gone.

I was just able to gap them to spec again, and it ran much better for a minute or two before they fouled up again.

I will install new points and make sure the shaft is smooth and lubed up. I think that is problem solved.

I appreciate everyone's help. Just being able to talk through it often forces me to sit back and think about the issue, and often come up with a solution.

Cheers

While your at it you might want to get new plugs. I recommend NGK3112 spark plugs that it what I run in my WD45

Actually, good idea. This tractor came with Champians in it... they look good, run fine, but I have read lots of recommendations not to use them.

Well if the old plugs are black and sooty good chance there not working as well as they should be and should be either cleaned or replaced and if champs I'd get new NGK3112 plugs they tend to hold up better then most other brands do

You have about every solution possible and sounds like a good tune up is in order. If you can drive the tractor 1/2 mile one day with no problems and nothing but problems later I always suspect moisture in the fuel and some freezing with that much cold weather. Back in the day Heet was a standard additive when it got cold but I seen manifolds frost up and we suspected the same on the inside. Hard to fix anything with 3 feet of snow in front of you but does it run okay in a heated shop?? Maybe time for a fresh supply of fuel? cleddy

Definitely a concern around here! The tractor was in the cold shop overnight, so I know it didn't take any melted snow in or anything. I haven't got the shop heat on yet, but letting it get up to operating temp at idle didn't change anything.

I have a suspicion that the root cause is a failing condenser. Last night I sanded the points to get all the pitting out of them, and installed them back in. Barely got my 20 thou gap, but it started up. Idles beautifully, but doesn't want to rev up or take any load. Between this, and the pitted points, it points (in my experience) to a bad condenser. I'll be picking up a tuneup kit tonight.

Will post back once I get the kit installed.

Thanks.

I haven't replaced a condenser on any engine in over a decade. Condensers now days tend to be bad right out of the box and an old one almost never goes bad

Heyall, posting an update. Once again, the issue is with the engine barking and seeming to run lean when off idle. Idles better than my truck.

There is some good and bad...

1) I installed a points and condenser and rotor. Points are sparking bright blue, and now have lots of adjustment. Started up the tractor and there was no change.

2) I needed to hold onto the ignition switch for a minutes to thaw it out. It's a push/pull, and was frozen up. I wondered if this could contribute, so I decided to make things as simple as possible, and bypassed the entire wire harness which I had recently built to convert to an alternator. I ran a wire directly from the battery to the (brand new 12V) coil. The engine started and ran perfectly! I proceeded to back out of the shop, put the grader blade back on, and cleared up and down my lane a few times. Not a hickup.

3) Delighted with my success, I decided to then wire the ignition to the light switch. It is a two step switch. Installed ignition on the first click, and lights to the second. This also allowed it to start charging again. I started it up, and went for another pass down the lane. I made it right to the end of the lane before it started barking, and then died.

4) Now I am back in the shop, and the tractor is doing exactly the same thing as before. I can't get it to run properly even bypassing the electrical again. Points are still flashing bright blue, carb is clean (i know because i checked AGAIN) and the spark plugs are all firing.

I do plan to replace the plugs once I can get to town again. I timed the engine with a light, but is there something that could be changing internal to the distributor drive? Grasping at straws here... I am out of ideas.

Very much appreciate your thoughts.

Cheers.

How are the plug wires and cap? Poor wires and a bit of moisture (snow) can do strange things, as can carbon tracking in the cap or on the rotor.

Does your carburetor and manifold form visible frost on the outside of them when running? If so, I have seen some heat shields built to hold some of the exhaust heat around the carburetor and attaching area of the manifold.

A bit of frost around the carb right after starting. What does this mean?
Wires and cap are not new, but they look good. Now that you mention it, I'll just replace them.

Not sure if it's the root cause, but I made a discovery. I just pulled out the distributor completely and put it on the bench. I couldn't turn it by hand. In fact, I could barely turn it with vice grips.

I removed the timing advance dogs and springs, and the center spinning piece that actually does the advancing is solid. I now have the dizzy spinning after soaking in penetrating oil, but working on removing the rest of the bits to get them freed up.

When I first got the tractor running, I set the timing with a light. Since the advance isn't working, this means I am running retarded at idle, and fine at full RPM. However, if the timing did manage to advance itself, but not return to where it was, then I would be very advanced at full throttle. Could be?
It's stuck enough I'd be shocked if it could have move.

To be honest I can't believe the drive gear didn't get ruined, but all the bits look okay.

Probably still have another issue somewhere, but glad I caught this.

Frost around the carb where it hooks to the manifold is common and just says the carb is working as it should be.

One way to check if the distributor cap might be going bad is fire it up and put your hand on/around the cap. If you let go fast due to getting zapped it is bad. Years ago we had a GMC pickup that when ever it got wet out side it would act up. My dAD TOOK IT TO a number of shops and none could figure out the problem. Last shop he took it to I was there when it was picking it up and they had not found the problem I told my dad to start it and I grabbed the cap and got zapped big time. They replaced the cap and rotor and that fixed the problem. They tried to charge my did for fining the problem and he told them NO way unless your going to pay my son for doing your job

That's a great story... I have used the same technique, just not on purpose! My trick was to spray the engine with a mist bottle while it was running at night or in the dark, and look for arching. Works well.
I have new plugs and wires on order; expecting them tomorrow.

I had my distributor soaking in diesel all day. After work I tore it right down, and got the advance mechanism working perfectly. Cleaned the 100 year old grease out of the housing as well and put that back together.

It took a few tries but I got it to start again, and then put the timing light on it. I now have it running like a watch, and the timing advance is working as it should.

When setting the timing, at one point I went the wrong way and retarded it too much. It started to bark just like before, but runs great once I got it in spec. I am really hoping I have it solved now. If by chance the timing advance was moving and sticking, it would explain why it happened intermittently, being way too restarted sometimes, and then fine others.
I just spent 10 or 15 minutes with blade dragging snow around, and no issues at all. Hopefully the gremlins don't come back. Fingers are firmly crossed that it's solved.

Funny how troubleshooting evolves though... this carb issue thread has covered a lot of ground
Thanks for all the help guys!

Have you thought about checking the valve lash and setting it. These tractors have a tight lash. You might have a tight valve and on heat up keep the valve from fully seating. That can cause your barking as u call it. Plus run a compression check. A float that is off a bit is not going to cause barking.