Carburetor And Black Smoke Info (Long)

This is kinda long, but I just wanted to pass this info on 'cause it was a new one on me and you guys may or may not already know 'bout this.

I thought sure that I was going to have to buy another one of these Marvel-Schebler carbs, as I have overhauled about every kind of carb known to mankind and this one really had some really weird symptoms.

It ran fine at idle and seemed "pretty good" at wide open throttle, but anything in between it would just absolutely "fog" black smoke. Wasn't flooding per se, just pulling too darned much fuel. Ran way too rich and just gassed something awfull. Just absolutely sooted up the plugs.

The local red shop had ran it thru the carb cleaner and put a kit in it and this is why I figured I needed to pitch it and buy another good one. It acted just like someone had drilled out the main jet too darned far.

On top of everything else, it did not have a high idle adjustment built into a shutoff solenoid like the book stated. It just has what looks to be a brass plug with a metering jet on the inward side. Above this "plug" is where the main pickup tube with a larger second jet lives.

Anyway, at the end of the day, this main metering tube (# 33 in the drawing, second picture) is threaded and has to be adjusted for height (and richness) by varying it's depth in the bore of the bowl. Screwing it in further (raising it's height in relation to fuel level) leans out the carb; turning it back out or lowering the tube in relation to the fuel level enrichens the carb at anything higher than an idle speed.

First time I've ever had to remove a plug and reach in and adjust a carb from the inside. It really had me goin' fer awhile there. But, by adjusting that tube height position in the bowl, it cleaned 'er right up and she runs like a new one now.

Maybe this will save someone else a headache someday. :>)

Allan

Well, what had me baffled was that the local red shop had just put a kit in the darned thing.

Perhaps he either didn't take that tube out or had just given it a generic setting, I don't know.

It's kind of a pain to set 'cause ya have to shut the fuel off and drain the carb with each try. But anyway, that is the little bugger to adjust.

Yeah, I think your 656 should be the same animal.

Saw your buddy the other day in the parts store. He's gettin' along fine since he got married and settled down a bit. :>)

Allan

Yep, I just couldn't understand fer the life of me, why the tractor didn't have a high idle enrichment needle. Just didn't make any sense.

Like Hal says, they "hid" it inside the darned thing. :>)

Allan

I 'spose all those old IH mechanics knew about this; I just happened to stumble on to it kind of by accident.

But, that is exactly what is going on; that tube height has to be set just right in relation to the fuel level to pull the correct amount of fuel over the top.

What finally turned on the lights for me was that the first time I put 'er back together, it was then running way too lean and wouldn't run at WOT without the choke being pulled out a bit. So, back in I go and adjust 'er down (screwed the tube out); it cleaned 'er right up.

New one on me. :>)

Allan

The engine was basket case except for the block.
I never had one of these apart so I talked to one of my co-worker's as how to split the case. He said to keep all chisels and screwdrivers away and
showed me where you could pry and split the case.
No gaskets were used between these surfaces.

I had the crank ground .010" under and installed new cylinders & pistons. Had more trouble figuring out where the sheet metal went than anything else. Fired up the engine and it didn't have any power out on the road. Tried everything. Had the carb apart several times.
The engine even smelled hot. Finally called the local VW garage again I think this was the 4th time. I talked to one of their techs and he said
to remove the red plastic plug from the carb. My VW manual said not to adjust this. He said to back the screw out 1 full turn and see if that helps. I backed it out 2 turns and it made the
biggest difference. That was about when the first energy crunch hit the US and I kept the car.
I ran straight 30wt oil year around and it never failed to start even below zero. One of the old piston's had a hole burnt through from running lean. Hal