Help; the case mechanic is stumped

[carlevans]

I'm having a problem with my 1947 cub that was purchased new by my grandfather.

After warming up the tractor will loose power and the engine slows down. This happens fastest under load. Pushing the clutch in will not regain R.P.M. Choking makes no difference except to flood the engine out. Shutting it off and restarting will bring it back temporarily. Sometimes backing off the throttle lever and shoving it ahead will get it to open up until it does it again.

The governor is open to full throttle when the cub is not opening up.

The tractor does not miss. When running good or acting up it runs smooth and does not miss a beat.


Things I have tried:

Cleaned the carburetor twice. I used carb cleaner and ran a small aluminum wire through all the jets and openings. Pulling the drain plug in the float bowl will get a steady stream of gas; I also cleaned the sediment bowel and the oil bath air cleaner.

I put on a new coil and new spark plugs.

I drained the gas tank and replaced with fresh gas.

I left the tractor at the local case-ih dealers last week. The mechanic says he is stumped. Any ideas?

[Max_Wedge]

I'm having a problem with my 1947 cub that was purchased new by my grandfather.

After warming up the tractor will loose power and the engine slows down. This happens fastest under load. Pushing the clutch in will not regain R.P.M. Choking makes no difference except to flood the engine out. Shutting it off and restarting will bring it back temporarily. Sometimes backing off the throttle lever and shoving it ahead will get it to open up until it does it again.

The governor is open to full throttle when the cub is not opening up.

The tractor does not miss. When running good or acting up it runs smooth and does not miss a beat.


Things I have tried:

Cleaned the carburetor twice. I used carb cleaner and ran a small aluminum wire through all the jets and openings. Pulling the drain plug in the float bowl will get a steady stream of gas; I also cleaned the sediment bowel and the oil bath air cleaner.

I put on a new coil and new spark plugs.

I drained the gas tank and replaced with fresh gas.

I left the tractor at the local case-ih dealers last week. The mechanic says he is stumped. Any ideas?

Could the clutch be hanging up, then after you shut it off it frees itself then it hangs up again? I think I would look at that and also look at what kind of shape the tank is in. Is there scale and rust in there that could be plugging up the fuel hole? I will continue to rack my brain for ya'.
Max

[Eugene]

Check the valve tappet clearance.

Eugene

[John *.?-!.* cub owner]

alos oil pressure and coolant, but I assume you have done that already.

[carlevans]

Thanks for the help.

When the tractor looses power I can take it out of gear and the engine does not come back up to speed. And I can shove the tractor around by hand. If the clutch were hanging up I don’t think I could do this. I cannot see any rust or scale inside the gas tank. The sediment bulb was clean when I cleaned it and the screen. The sediment bulb is clear glass so I can see any contamination. There is none. When I pull the plug on the float bowel I get a good flow of gasoline. When it acts up I have time to get off the tractor and check the governor arm to make sure it is open. The tractor will not come back if left sitting when it looses power. If I shut it off and restart it - it will come back. Sometimes it will come back if I work the throttle lever without shutting it off. If the problem were corrosion in the tank or line I don’t think it would unplug without movement of the tractor or vibration to loosen it

I will check the valve tappet clearance. However I think the engine would continuously have a lack of power if that were it. The engine does come back to full power and will run good for a while. I wish it would act up continuously, and then it would be easier to track down the problem.

The oil was recently changed. It is clean and has good oil pressure. The coolant level is normal.

Because the lose of power occurs at irregular intervals I’m leaning towards fuel or electrical problems.

Any other suggestions?

[JimT]

Condenser maybe? I've seen these little things do strange things.

JimT

[Mike in Louisiana]

Is the vent in the gas cap pluged up? Loosen cap when it acts up.

[Andy Oberg]

I think you're on the right track. When it happens, I would immediately do some voltage checks to eliminate that as the source. As is usually suggested on these kind of problems, check all electrical connections for good contact and good grounding.
When you say it loses rpm, does it die or keep running smoothly except at a lower rpm? Any sputtering?
My 78 has a notch worn thru the catch on the throttle lever and just kicks out to a lower rpm ever so often. A little JB weld or a trip to my friendly welder is in store.
Good luck and keep us posted on your findings.

Andy

[carlevans]

When it acts up it keeps running at a lower RPM. Almost like I had pulled the throttle back. Even though the throttle remains wide open it will not rev back up when I take it out of gear. If I pull the throttle back to an idle it will slow down. It runs as smooth and even as any cub I've ever seen. It does not miss and there is no sputtering. That is what has us stumped.

Thanks for all the help

[Donny M]

When the loss of power occurs, quickly disconnect the linkage from the governor rockshaft to the carb. Try increasing the RPM by operating the throttle on the carb by hand. If the RPM's increase by hand, look to governor troubles.

[Eugene]

I will check the valve tappet clearance. However I think the engine would continuously have a lack of power if that were it. The engine does come back to full power and will run good for a while. I wish it would act up continuously, and then it would be easier to track down the problem.

The described symptom is typical of a very small valve tappet clearance.

Check the valve tappet clearance. It's an inexpensive check. If the clearance is correct then you have ruled it out as a possible source of the problem.

Eugene

[John *.?-!.* cub owner]

I think that if it were valve clearance it would have too cool before returning to normal, not just start right up. I would check the distributor shaft for play, maybe causing the point gap to change. The other thing I would wonder abobt is governor linkage to carb., either loose or binding.

[Eugene]

I'll wager 5 cents and my sweat soaked, salt rimed, unwashed, dirty, grease stained, Edward Jones Investments ball cap on this one. Valve tappet clearance is to small, especially on the exhaust valves.

As soon as I can get someone to wager items of comparable value, I will explain why, after shut down the engine will start up and run fine for a short while.

Eugene

[splicer]

OK Eugene, your on!!!.........I'll bet you 5 cents and my worn out, cow dung encrusted, holy soled, broken laced, stinky, toe jam filled combat boots........Let's hear it!

[Andy Oberg]

I like the debate. And in this corner...
I'm waiting for the answer, too but I've got nothing near as cool to bet.
Wager on!

Andy