Wed Jul 17, 2013 11:36 am
My Cub has been running well until the week of July 4, when I took it to my Miss. farm. I ran it for a couple of days, mowing with the belly mower. No problem. I shut it down and hosed the dust off, being careful to keep the water away from the ignition and fuel system. Well, since that time I have been unable to get it to run properly. Cranking is a problem, and when it does crank, it won't do more than idle. If I put a load on it, it dies. I was convinced that it was a fuel problem, so I pulled off the carb and cleaned it out thoroughly (two times), blowing out the orifices. There was no water or trash in the carb bowl and the float/needle valve seemed to operate properly. Fuel flow from the gas line appears sufficient. I was able to get it to crank, but still with no power. When I got back home to Birmingham and internet access, I posted my problem here on the forum. The general consensus was that I must have gotten water in the ignition system. I opened the magneto and used my heat gun to blow off the cap and internals. Now after a couple of weeks garaged in the dry (air conditioned, too) there is still no improvement. As I still think it may be fuel related, I brought the carb from my 1947 Cub home with me. I cleaned and installed a rebuild kit. Just this morning, I swapped out the carbs. The tractor cranked on the first try, and seemed to idle very well, but will not run under throttle. If I open the throttle by hand it bogs down. It reminds me of the time years ago when I installed a Carter AFB and Edlebrock 4 bbl manifold on my 1972 2000CC Pinto. (It didn't run too well.) I was able to roll back into the garage at idle, but it will not take any throttle. No changes or adjustments have been made to the timing,ignition or governor. I am out of ideas. I can't wait till the DSCF to get this problem resolved. Any suggestions would be greatly appreciated.
Last edited by thiggy on Wed Jul 17, 2013 12:31 pm, edited 1 time in total.
Wed Jul 17, 2013 11:52 am
Did the governor spring break and is the governor throttle lever moving? If those are fine maybe the carb. main jet is restricted or possible float not set right.
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Wed Jul 17, 2013 12:03 pm
Unfortunately, the governor spring wouldn't cause it to bog down and die. You just wouldn't have any throttle control.
You mention fuel flow is "sufficient." It should be running a full pencil-size stream out the pipe. Anything less than that indicates a fuel blockage that could be causing your problem. Do you have an inline fuel filter? Try without the filter.
Run a dollar bill between the points to clean them up.
Have you checked the spark?
Does pulling the choke help at all?
Wed Jul 17, 2013 12:56 pm
I hate water on my machinery. I strive to shed my equipment every night for this reason. Once in a while a downpour may catch me out in the field or I have to use water on the wheels and fenders when I get my equipment all mudded up in the field. Very rarely, I will carefully wash off the tractor with water, taking care not to use water under force and to stay away from problem areas. My main cleaning method is the electric leaf blower to get grass, dust, dirt, and other loose debris off the equipment. Air is much better than water because water will saturate debris that sits in crevics which acts as a "sponge" to sit there and cause rust to form. Water can get into ignition systems, seep into threads and rust the fasterners, get into instrument guages and switches, destroy contact points in wiring systems, sneak into transmission cases and bearings As you can tell, I hate water around my machinery
Wed Jul 17, 2013 1:38 pm
I'm guessing you checked for a blocked air supply, good fuel flow, and a strong blue spark. If all those things are good then I'd check the timing.
thiggy wrote: If I open the throttle by hand it bogs down
thiggy wrote: No changes or adjustments have been made to the timing,ignition or governor. I am out of ideas
How or why it'd change I can't say.
Wed Jul 17, 2013 3:57 pm
It would only take 20 minutes or so to do a compression test on it. You never know maybe you've got a stuck valve or a piece of carbon under a valve seat or something like that. My '53 didn't run when I bought it but I got it running in short order. It would idle but that was it. It wouldn't pull itself even on the flat. It had 2 stuck valves.
Wed Jul 17, 2013 4:19 pm
Thanks for all the responses. I have an original style fuel delivery - steel line, glass fuel bowl, strainer. All appear to be clean. Checking the fuel flow is not particularly simple, since with the steel fuel line, I have to remove the carburetor to be able to check the volume of fuel flow.
Wed Jul 17, 2013 4:22 pm
thiggy wrote:Thanks for all the responses. I have an original style fuel delivery - steel line, glass fuel bowl, strainer. All appear to be clean. Checking the fuel flow is not particularly simple, since with the steel fuel line, I have to remove the carburetor to be able to check the volume of fuel flow.
Remove the plug,on the bottom of the carb, or the main jet, to check fuel flow. Ed
Wed Jul 17, 2013 4:24 pm
Have you looked in the fuel tank to see if there is an obstruction at the outlet? Sometimes trailering can dislodge debris that will then move around and block the hole. Also, checking fuel flow by removing the carb only checks it TO the carb, not THROUGH it.
Wed Jul 17, 2013 10:16 pm
What Don said about a gas tank outlet obstruction happened to me. Jiggle the gas tank while watching with a flashlight. There may be a very small particle of rust or debris floating around.
Also, if you've disconnected the carb you may have hooked up the levers wrong, or the governor linkage needs adjusted.
Someone described a clear plastic tube to connect into the carb drain hole in the bottom of the carb to see the gas level while running the tractor. I've used this and it can tell you a lot about the float and gas level inside of the carb as you throttle up or down.
It does seem odd that all was fine until you washed the tractor. That would seem to indicate water somewhere, but maybe it is just a red herring, as they say.
Wed Jul 17, 2013 10:30 pm
ECHO Ricky Racer. Start with a compression tests, then valve tapped adjustment, check ignition timing/firing on each cylinder with timing light. Basically, conduct a complete, 100%, tune up.
Your have an ignition problem. But eliminate the easy stuff first. Diagnostic process.
Wed Jul 17, 2013 11:40 pm
Maybe you got water in the air filter bowl?
Try running with the rubber tube from the filter to the carb off?
Long shot, but just maybe.
Thu Jul 18, 2013 12:14 am
Fcubman, no, no smoke of any particular kind.
Thu Jul 18, 2013 5:39 pm
thiggy; I reread your posts on this thread and I don't see that you said anything about checking the throttle linkage. When you move the throttle does the butterfly at the carb move? Also, have you tried to choke it while running? If so did it run better or worse?
Another thing to check is point gap. If the gap is off by more then a couple thousandths, it can throw the timing off enough to lose power.
Thu Jul 18, 2013 10:23 pm
Birddog, the throttle linkage opens the butterfly as it should. If the choke is applied when running, the engine dies. I plan to check the point gap, the plugs and compression tomorrow, but I am just sure that the issue is fuel delivery, one way or the other. Will removing the carb jet in the fuel bowl be a satisfactory way to check for adequate fuel flow from the gas tank?
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