Carburetor woes

I've been whining here about my non-running B, and I need some more help with a carb question. I posted photos of my Marvel Schebler carb some time ago and was told it wasn't original to my B. I bought a crusty Zenith through eBay that the seller claimed was from a B. I scrubbed it clean inside and out, boiling it in lemon juice (which smells really bad). I timed the tractor once again and now it will run for a second or two on starting fluid. I'm guessing I've narrowed the problem down to the carb, even though it responds the same way with either the Zenith or Marvel Schebler in place. I replaced the F-M magneto with a later distributor and new coil. The distributor puts out enough juice to cause a lot of pain, which I take as a good thing.

My owners manual indicates there are just two adjustments for the carb - idle and air/fuel mixture. My "new" Zenith also has what looks like an adjustable main jet. Does anyone know the baseline adjustment for that? I adjusted the air/fuel screw 1.5 turns out and left the idle alone.

Also, can anyone tell me if my reasoning about the no-start problem being carb related makes sense? I bought this as a non-runner from an old man who claimed he had it in storage and started it once per year, and it wouldn't start the year I bought it. I'm guessing it was sitting around a lot longer than he claimed. It still won't start after a starter motor rebuild, overhauled distributor, and cleaned up Zenith carburetor (without use of ether).

Thanks gentlemen.

  re clean carb again  if it runs with ether  it will run on gas also try it  no fuel

If this is the Zenith carburetor you bought and the adjustment screw is at the top it would be the idle adjustment only. With this carburetor you have only an orifice in the power jet at the bottom that meters the  proper amount of fuel.

If this is your carburetor did you remove the plug at the front bottom, then remove the brass power jet along with the brass feeder tube/discharge jet on a slant in the neck before you boiled it? If not you would not have done any cleaning behind the power jet and below the feeder tube. After the fuel is metered at the jet it must have free flow from the jet and up the feeder tube into the engine. If it has a adjustment needle in the front you still need to remove the power jet and feeder tube before boiling.







Edited by Dick L - 15 Aug 2010 at 8:35pm

Power jet main jet all the same thing different words from a different area.

Setting is simple. you turn it out a coupla turns or so. I think the book calls for 2 1/2 turns. Same with the idle screw at the top. You first set the idle after you get it running. The butterfly stop screw on the back sets the idle rpm (amount the butterfly is open) and the air/fuel mixture (idle) screw is set to run the engine smooth at that butterfly setting. You have to work back and fourth between the two to get it set to idle.

After the idle is set you open up the throttle wide open and adjust the power/main jet to run the fastest RPM and then turn the needle back in until you detect a slight slowing of the RPM's. that is it.

 

Scott,

good  input - wished I could work on this full time - will wait and apply advice this weekend.  I like getting back to the basics where you can work on something.

Last, but not least...

Check the intake path, and exhaust path... for blockages.

I bought a CJ-7 once... guy was frustrated-to-heck, 'cause it'd run find for about a half block, then die.

I ran into same problem with my B last winter... ran for about three seconds, then die.

CJ:  Mouse built next in muffler... using trash from garage... paper cups, plastic baggies... found it 'cause I unhooked the header Y-pipe, and it ran fine...

B:  Oil-bath Air filter... full of water... frozen water... not Black Gold... not Texas Tea.

And always, always, always... pull the fuel line, let it drain into a jar, and see how fast it flows... then remove the fuel tank cap... if it flows faster, the cap isn't venting properly.  If it flows slow regardless, blow a little compressed air backwards, then see if it flows faster.  If it does, you've got crud in the tank, line, and/or sediment bowl.

If you have the latter, drain it all.  Yank the line, blow it out 'till it's super clean.  Thorougly clean or replace the sediment bowl.  Drain the tank, plug the sediment bowl port, throw in two handfulls of 3/8" hex nuts, and tumble the tank... ratchet-strap it to a tractor wheel and go for a nice, leisurely drive... and rotate the tank, so that it gets scraped clean.  Then dump the crud and hardware, hose it out (water) then use a shop vac with a piece of 1" conduit taped to the inlet (as an extension nozzle) to suck out any remaining debris... then reverse the hose and blow lots of warm air through it to dry it out... reassemble and enjoy.

Whenever you purchase anything that's been sitting for years, the fuel tank and the fuel system is the first thing you want to clean out top to bottom. Old gasoline turns to muck when it sits for years, especially at the bottom of the tank! Put fresh gas in it, and it starts to loosen all that muck! I think you see where I'm going with this. In your case with your Tractor, ( as with many others) pull the tank, get it cleaned out at a radiator shop, and have them seal coat the inside. While they have the tank, disassemble the rest of the fuel system and clean everything up. Fuel line, sediment bulb, & carburetor. After that is done, yank the valve cover and roll the engine over by hand watching that ALL valves are moving up n' down like they should. If you been cranking on that engine with the valves stuck, you could have some bent pushrods, and or valves stuck open. Once you know for sure everything in the valve train is working, oil it up, re-install the valve cover and wait for your tank. Once your tank is back in place, install fresh fuel and give it a whirl. If you have spark, and you know you have fuel, it should fire right up. Its rare that anything that's been sitting for years that's had old separated fuel sitting in it's tank starts right up and runs nicely.... HTH
Steve@B&B

Good call for those who mentioned stuck valves. Only the rear four rocker arms (cylinders 3 & 4) move when turning the engine over by hand. Rockers on the front two cylinders don't move. I hit the valve end of the rockers with a big old hammer, only to have the pushrods come flying out. I'm guessing they should be replaced. The four of them look less-than-straight.

I've learned that just dropping the pushrod into the hole doesn't work. You have to wiggle it around before you hit cam lobes and it will rise and fall normally. That, or my pushrods are just badly bent. Am I doing anything wrong, other than trying to reuse bent rods that I straightened with my hands and eyes? It seems like you shouldn't have to do anything fancier than drop the rod in the hole - right?

I'm slowly learning that just because I seller says the tractor started last year with no problem, I shouldn't necessarily believe him.


Edited by Scott in MA - 17 Aug 2010 at 9:45pm

Thanks for the info on reinstalling the rods. I only have the owners manual, not the repair manual for this B. Can anyone tell me what the valve/rocker clearance should be and what mark on the flywheel I should use the adjust the valves?

Scott, I didn't spot this point above so will add it. Check your push rods for straightness. Easy way to do that is to lay the rod on a flat metal surface and roll it back and forth - your fingers will quickly tell you if the rod is straight or not. You can straighten a bent rod by TAPPING on it with a ball peen hammer - locate the high spots (as above) and give the rod a tap or two until all the high spots are gone. Keep working at it until the rod will roll smoothly with no high spots. Doesn't take long - probably taking me longer to type all this than it will for you to check and straighten one!

The B started tonight after I unstuck the valves and rockers in number one and two cylinders. The valves must have been opening slightly because I was able to time it from compression on number one (before taking it apart). Thanks for all the advice.

It made a beautiful, yet very loud sound (no muffler). I went up and down the driveway many times before stopping for the night.