1950 6 VOLT SIDE MOUNT SPITTING BACK

Have done a lot of work recently to make the tractor start and run like it should.

Changes I've made: New 6 volt generator, new starter, new manifold, new points plate, new plugs, wires and rotor, overhauled carb and replaced venturi. I soaked it in carb cleaner and blew out all the passageways as recommended by everyone.

Cold engine compression readings:
Nr 1; 50 valve seating. 120 final reading. 150 with 1 teaspoon of ATF in cylinder

[b:7f0cf1a34a]Nr 2; 30 valve seating. 50 final reading. 130 with 1 teaspoon of ATF in cylinder[/b:7f0cf1a34a]

Nr 3; 60 valve seating. 90 final reading. 140 with 1 teaspoon of ATF in cylinder

Nr 4; 70 valve seating. 90 final reading. 100 with 1 teaspoon of ATF in cylinder.

Adding the oil brought the compression reading up to specs. I've heard it could be rings or valves. Yesterday, I ran about a quart of ATF through the carb to see if it would help. Didn't matter too much. After fogging the engine with ATF, I took a quick reading on the offending cylinder without removing the other plugs, but air cleaner was disconnected. Got max reading of 60 PSI. I would be grateful to hear more discussion and possible remedies on the sick cylinder. It runs and idles good at 500 RPM - any lower and it wants to stall. I've had the tractor about a year and the gentleman I purchased it from said the tractor was recently overhauled - Which I believe. Tractor doesn't smoke or use oil. It has good oil pressure. The plugs are clean. I had the governor off to replace the shaft seal and gasket and noticed it had a new timing gear. You can see where RTV squished out between various gasket mating surfaces.

My original problem was the tractor was hard to start which was likely due to a vacuum leak. The tractor starts reliably now but it spits back through the carburetor when you throttle it up.

Two questions:

1. What does the compression readings tell you?
2. Where should I look to fix the spitting back issue? Believe it's carb related as it wasn't doing this until I overhauled the carb.

Thanks for your help!!

Dollar Bill,I think that I would pull the valve side covers and check the valve clearance.It sounds to me like the intake valves may not have enough clearance,thus the popping,spitting out the carb.Maybe the exhaust valves also.
Intake .010 - .012 cold
Exhaust .014 - .016 cold

Dollar Bill,I forgot to add that If after you adjust the valve clearance its still popping out the carb.Maybe the guy that did the overhaul didn't replace,or reface the valves or grind the seats properly.The valves may be leaking the compression.

Well, generally, if compression increases after adding oil to the cylinders, it means bad rings.
I'm not sure what the valve seatings readings mean.
To do a compression reading, the rule of thumb has been to remove all spark plugs, (it would be a good idea to pull the coil wire) and open throttle all the way.
Also, backfiring through the carb could be an indication of timing being off.

HTH
Chuck

Thanks Guys - I'm out of town until Friday. I'll check the valves and post back with the results. I hope a valve adjustment will take care of it.

Is it just coincidence the spitting back started after I overhauled the carb?

[b:c8307a1c5c]Update:[/b:c8307a1c5c] Better compression readings - Still have the spitting back problem.

Compression readings are much better (95-100) with a new gage. Whew!!

Pulled carb back apart and verified everything was clean & tight.

It now idles down to 500 RPMs - Idle mix screw screwed all the way in for highest RPMs. [b:c8307a1c5c]Is this bad?[/b:c8307a1c5c]

Installed new made in USA distributor - Bushing in original severely worn.

Runs okay except it spits back through the carb intermittently when you throttle it up. Some times when you give it the gas, it revs up like it should and then other times it spits back until it reaches the governed speed and then smoothes out. I moved the distributor timing around and it didn’t seem to help. [b:c8307a1c5c]I'm stumped!! What else can I try?[/b:c8307a1c5c]

(quoted from post at 21:26:26 11/01/08) Seems like the more I fix it, the worse it gets.

Compression readings are much better (95-100) with a new gage. Whew!!

Pulled carb back apart and verified everything was clean & tight.

It now idles down to 500 RPMs - Idle mix screw screwed all the way in for highest RPMs. [b:d8c2f4906a]Is this bad?[/b:d8c2f4906a]

Installed new made in USA distributor - Bushing in original severely worn.

Runs okay except it spits back through the carb intermittently when you throttle it up. Some times when you give it the gas, it revs up like it should and then other times it spits back until it reaches the governed speed and then smoothes out. I moved the distributor timing around and it didn’t seem to help. [b:d8c2f4906a]I'm stumped!! What else can I try?[/b:d8c2f4906a]

Click to expand...

Is yer float set right!?!?!?

It checked out at 1/4" - so I didn't bother it.

Is the idle mix screw setting and indication?