how does older carb work? mine won't stay running.

[canucklehead]

I found a Zenith VN carb diagram. I have the "float arm pivot assembly" (flap) positioned correctly. And the groove on the float should be at the bottom.

I was close on describing the "block". Zenith calls it "emulsion block" On the bottom/underside of that emulsion block is a mainjet and a compensating jet. The 2 brass jets I removed (there are 2 stacked on top of one another on the top of emulsion block) are essentially pilot jets.

They call the accelerator pump that is stuck "pump piston". There is also a pump spring under it, and a pump check valve.

Even if this pump gives a squirt on acceleration, if all the jets were working I should still be able to run without manually dumping in fuel. I think the jets on the underside of the block may be plugged up.

So folks, what's the best product to soak in to free up these stuck pieces, and to give me a chance to remove that emulsion block screw? can I use mild heat on that screw to help persuade it? Impact driver?

 

[DFB]

Sounds like you got it figured out what you need to do.

The Zenith/Bendix on my old Harley operates similar and also has the accelerator pump which as described earlier gives that xtra fuel when the throttle moves. If your float bowl is filling up with gas (and not overflowing) the float is asy probably works ok and its still more than likely you have a plugged jet circuit especially if it runs when you put additional gas into the venturi. When solvents and compressed air wont clear a jet it helps to have a wire tool like this Carb-Cleaner-Wire-Set. Others use a similar tool made for cleaning welding tips.

On that stuck screw best bet is a soak with a penetrating fluid. Kroil is one of best you can get. PB blaster works for me too and really good tight fitting screwdriver tip. A little impact never hurts.

 

[canucklehead]

unfortunately the main jets are on the bottom of this emulsion block so I can't get at them until I remove the block. I'm guessing they get the bottom sludge first as it seems to settle lower in float bowl.

another guy told me he drilled out bottom of float bowl cylinder area where the accelerator piston goes up/down, tapped out piston, cleaned it up and then JB welded the drilled hole. He says it doesn't leak. If i can't unseize, I might try that.

 

[jimmysisson]

But not an impact driver! I'd soak it a couple days then try to tighten the screw(s) just a whisker. That often will break something loose you've been trying unsuccessfully to turn out. Even when it frees up a bit, turning out and in a bit over and over eases the strain on parts.
Those jets are prob key to good chance of running right, along withe the pump.
Good luck with the old girl.
Jim

 

[canucklehead]

I was able to remove the emulsion block. I hit the screw with one smack with impact driver (after it had soaked in diesel) and it busted loose easily.

yep, the bottom 2 jets were covered in white sludgey slime. it is scaley where it dries, and like a thick vaseline gel where it's been wetter. My theory is this is from that awful ethanol in fuel. Or does normal gas just turn into this?

the piston still won't move. Now have the piston covered with PB Blaster. If that doesn't work. I'm moving to the next snake oil= nitrolube. Actually made locally, and according to them...the best ever.

so, if i ignore accelerator pump and piston, this should still run ?? the pump just gives it a little shot of fuel when you accelerate (?). So if I don't have this, maybe I'll just have a delayed response when I throttle up....kinda like poorly tuned high/low screws on 2-stroke stuff (?)

 

[Arkaybee]

Get a gallon can of Berryman Chem-Dip; comes complete with a basket inside in which to put the parts to soak by immersing the basket and parts into the can. Close it up and let it sit for the recommended time (it may take longer than you think for those small jet passages to be cleaned).

This stuff worked really well on a motorcycle carb that was stopped-up completely.

Be sure to read the directions and precautions carefully.

HTH

Arkaybee

 

[Car Doc]

I use what I call the wire tag method on all carbs. What it is is fine wire they use on those wire tags you see attached to things. Anyway sludge etc will settle in the lower areas of a carb and cause blockage in air bleeds and fuel transfer passages.

The wire will get better for cleaning the more bends it gets in it just keep it as straight as you can, run it thru everything with a hole and blow out with air. I use Berrymans b-12 its about the best carb cleaner I know of for cleaning old varnished gas etc out. hth

You want the accel pump working it helps with starting and helps keep the engine from leaning out and backfiring when trying to speed it up. It keeps the engine from hesitating in other words.

 

[DFB]

I'm sure you can get that pump piston moving again...give the penetrating oil time to do its thing.

 

[canucklehead]

:dance1::cool2:WOO-HOO!! I finally got this stubborn BOS (dyslexia) out!! I tried PB Blkaster for 2 days, diesel fuel before that. I tried Nitrolube. I still think they're all snake oils, but who knows. Tried heating it up with propane (didn't want to try oxy/acetelyne). NOPE.. none of them did the trick. I knew I couldn't drill from bottom and push it out because there is a check valve in bottom.

so I used a lefthand easy out, the one that looks like a drill bit. First I drilled the recommneded hole size (7/64th for a #2 LH easyout). I drilled through the top of the piston. It i s soft aluminum and drills easy. Then I put in the LH easyout, used a cresent wrench to turn it and it spun, then pulled out. I used wire wheel on my bench grinder to clean up piston and a deep socket with emery cloth to try and clean cylinder area on the float bowl. I also cleaned the spring on the wire wheel.

I used a 2 part gas tank repair compound to patch the hole I drilled in the piston. First I cleaned it good with brake cleaner, as brake cleaner leaves no residue. You rub it together until it turns grey, then put it on top. I would have used JB weld if I had any, but this is what I had handy.

here is the spring cleaned up:

here is the cylinder cleaned up. I tried to remove check valve at bottom but it felt like it'd strip so I stopped. I blew air through it and used carb cleaner:


here are 2 pics of the piston cleaned up:

 

[DFB]

:thumbsup: