440 backfires and will not run need help.

Blueford · Post by **Blueford** » Sun Sep 11, 2011 5:47 pm

It was running fine for at least 15 minutes pushed up some dirt, than it started missing and backfiring. I cleand out the bowl ( it had a lot of dirt) checked the fuel line drained the carb, it is getting fuel. I checked the cap and rotor looked fine. It will fire of and run for about 5 seconds than it stubbles and quits. I thought maybe some trash is in the primarie in the carb I didn't want to take it off until I have your opinons. thank you...Doug

JD440ICD2006 · Post by **JD440ICD2006** » Sun Sep 11, 2011 9:25 pm

While a carb can cause that kind of issue, all a carb really does is mix fuel and air. Many times, starting and running issues are in the ignition or valve settings or timing.
There is a screen in the inlet line going to the carb,be sure it is open. Make sure the float is set properly and does not leak.

jtrichard · Post by **jtrichard** » Sun Sep 11, 2011 10:47 pm

sounds like the main jet is pluged its running lean

Blueford · Post by **Blueford** » Mon Sep 12, 2011 8:14 am

If there is a screen I don't know were it is at. I took off the inlet line and the brass fitting no screen I also drained the bowl. The reason I feel it is carb related is it was running fine the not really it seems to be starving for fuel then it gets to much. Just a guess.

jtrichard · Post by **jtrichard** » Mon Sep 12, 2011 9:12 am

if it gets to much gas (rich) then it will run like crap, most likley NOT back fire and will smoke black..(lean) is back fire no power and run like crap you said there was dirt in carb bowl pull carb and make sure you get air thru every jet, vent, port, passage and it should run again

Paul Buhler · Post by **Paul Buhler** » Mon Sep 12, 2011 9:25 am

Hi: I'd pull the plugs and take a look at them. Recently mine fouled and when cleaned up, I was able to adjust the load jet better so that the mix is leaner - and the engine runs smoother - The load jet can vibrate open or closed if the glan nut is not snug and may give the symptoms you described. Good luck tracking down the gremlins. Paul

Paul Buhler · Post by **Paul Buhler** » Mon Sep 12, 2011 9:27 am

Deleted - duplicate post. Sorry. Paul

CELSESSER · Post by **CELSESSER** » Mon Sep 12, 2011 7:54 pm

Sounds like you plugged a jet. The dirt in the bowl would be good evidence of this. There originally is a small cylindrical screen in the brass inlet fitting of the carb. Not supprizing if it isn't still there, AKA the dirt in the bowl. That can be corrected by placing an automotive in line fuel filter (more effective IMO).If it was running good for a while before this happened the load jet and the air jet should be real close to the correct setting. Gently turn them in till they touch their seat and note the number of turns to reset them to after disassembly and cleaning(and recleaning to make sure) the carb. Be careful with the jets inside (brass, correct fitting screwdriver). Also remember that the "idle screw" on these M/S carbs is an air adjustment, IE the further you open (turn out) the leaner it gets and vica versa. Look at the brass tag riveted to the carb to see what number the carb is TSX_ _ _ I can look up what the starting adjustments are for your carb.

Chuck

Paul Buhler · Post by **Paul Buhler** » Tue Sep 13, 2011 9:19 am

Here's a link to the M/S and Zenith carbs manual.

http://l-36.com/carb.pdf

Tigerhaze · Post by **Tigerhaze** » Tue Sep 13, 2011 11:35 am

I have a M/S carb on my 8N tractor, and I cannot stress how important it is to adjust the three adjustment screws in the order and manner shown in the manual-otherwise you will pull your hair out trying to get it to run right.

Blueford · Post by **Blueford** » Tue Nov 29, 2011 9:25 am

I hope this helps others, I cleaned the carb, that did not help. I changed the points ,cap, rotor and condensor that did the trick. it is running a little rough but still running good. I think the condensor was loose anyway thanks for your help.

JD440ICD2006 · Post by **JD440ICD2006** » Tue Nov 29, 2011 9:29 am

Glad that you got it running.
Sometimes what appear to be carb issues are electrical, timing, valve adjustment, spark plug, or air restriction issues.
They will drive you nuts unless you eliminate one at a time to solve the problem.

Paul Buhler · Post by **Paul Buhler** » Tue Nov 29, 2011 4:14 pm

I changed the points ,cap, rotor and condensor that did the trick. it is running a little rough but still running good. I think the condensor was loose anyway thanks for your help.

I commented on another thread that I had the same problem; a poor condenser ground.

The electrics gremlins seem to be synergistic - a loose connection here, some corrosion or rust there, some cracked insulation, a faulty ground, weak distributor springs, worn ignition switch contacts, etc, etc. Sheesh.

I'm finally resigned to working my way through the whole system and upgrading the parts and wires as time, inclination and money allow. I really like it when the crawler starts on the first revolution or so and putters away happily letting me know it's ready to work.

I've rebuilt then disassembled and cleaned my carb at least twice only to find that the problem was in the electrics.

Good luck with your machine. Paul

FL450B · Post by **FL450B** » Tue Nov 29, 2011 10:10 pm

i have a case unloader and went on a big hunt to make it run right after a lot of trial and error i found the lobe that the point ride on had rust pit and wore away the wiper arm on the points after a short time it make changes in both timming and spark hunted for a new dist and could not find one but on a boat web site i found the same part# but still no part they talked about a kit for about 80 bucks to do away with points and cond it installed in about a half an hour my machine now starts right up and run better that ever the comp is pertronics hope this may help good luck

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440 backfires and will not run need help.

440 backfires and will not run need help.

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