Cub Loboy hard and slow cranking

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Pwalker21
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Cub Loboy hard and slow cranking

Postby Pwalker21 » Sun Mar 14, 2021 6:11 pm

Hello, New to this Forum. I just picked up a 1956 Cub Loboy and have been trying get it running. Did a full tune up plugs wires points fluids etc. The engine is very hard to turn over. Pulled the starter out of my Running 55 Cub I just fully rebuilt and still the same issue. Even bypassed the tractor cables with jumpers to the battery directly and still motor doesn’t really wanna turn over. Valves aren’t binding. Pistons are also moving. When I take the spark plugs out it will turn over but still seems weak. Any ideas?

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Urbish
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Re: Cub Loboy hard and slow cranking

Postby Urbish » Sun Mar 14, 2021 7:05 pm

Have you tried turning it over with a hand crank? If that is also hard to do, loosen your belts and see if it is still hard to turn over. Could have a bound up fan bearing or generator bearing.
Jim

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Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Sun Mar 14, 2021 7:48 pm

I just loosened them both and they both spin freely. I do not have a hand crank but with all the spark plugs out I can spin the fan and crank by hand. It has a brand new battery as well. As soon as I put 1 spark plug in the head you can tell the second it gets on compression stroke it struggles to push past.

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Re: Cub Loboy hard and slow cranking

Postby Eugene » Sun Mar 14, 2021 7:52 pm

Ignition to far advanced - - Ignition timing firing before piston it gets to TDC.
I have an excuse. CRS.

Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Sun Mar 14, 2021 7:58 pm

I thought the same so I checked the timing and it’s times exact. Also when the kill switch is on and it’s not sparking it’s still doing the same thing. So not any prefire resistance

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Re: Cub Loboy hard and slow cranking

Postby tst » Sun Mar 14, 2021 8:18 pm

bad/poor connections on battery cables? bad ground, try it with clutch pedal down in case something in the trans is bound up

Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Sun Mar 14, 2021 8:41 pm

Cleaned all cable connections as well as new crimps, why I by passed with the jumper cables to isolate. Just tried with the clutch depressed and now it will barely turn at all. Still the 6V system on the tractor just to mention.

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Re: Cub Loboy hard and slow cranking

Postby Glen » Sun Mar 14, 2021 9:12 pm

Hi,
6 volt Cub or LoBoy systems have to have larger battery cables than 12 volt systems.
If the LoBoy's battery cables are too small, the engine may not turn over as fast as it should.
I've bought a new battery to starter cable at Case IH, it says number 2 copper on the insulation.

The new cable for the 6 volt system at TM Tractor says number 2 in their description.

Someone could have put small, or 12 volt cables on the LoBoy.

If the battery is not fully charged, or has a problem, it won't turn over as fast as it should.

Jumper cables made for 12 volts many times have smallish wire.
If your jumper cables have small wire, it probably won't turn over as fast as it should, using them with a 6 volt system.
Some jumper cables have big looking insulation, but the wire is sort of small.
You might be able to look in at the ends and see the wire size. :)

Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Sun Mar 14, 2021 9:51 pm

I will charge the battery through the night, and check the gauge of the jumpers tomorrow. In theory of I was to disconnect the charging system could I put a 12 volt coil on and try starting with a 12V battery to see if the motor will fire?

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Re: Cub Loboy hard and slow cranking

Postby Waif » Sun Mar 14, 2021 10:25 pm

Are cylinder walls dry?
Oil pump primed?
If there's doubt , a little oil down the holes might help after some movement.
Good place for a hand crank...

Undersized or bad ground for the battery can make for slow cranking. (And sporadic no cranking.)
Transmission case gets used for a good ground after cleaning on some Cubs.
I use an angle welded to the platform on the 48. And it still fought me till a braided cable was used.
The 53 using the transmission housing as a ground spins along all happy. And could still use a bigger cable.

Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Mon Mar 15, 2021 8:24 am

I did spray some WD-40 on the top of the pistons and it did seem to help some. Is it possible the oil pump is bad? Or just not getting enough pressure because of the slow cranking to pull the oil up. The jumper cables are probably a 6 gauge because they do tend to get warm. But the original battery cable is 2 gauge and the ground is a braided cable mounted to the Tranny. Any thoughts on the 12v coil and battery idea?

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Re: Cub Loboy hard and slow cranking

Postby Gary Dotson » Mon Mar 15, 2021 8:46 am

Sure, you can use 12 volts to get it cranking. If you want to run it for a while on 12 volts, you put an inexpensive ballast resister in line to the coil, it's cheaper than buying a coil, if you already have a 12 volt you can swap it.
Did you prime the oil pump? They don't generally fail but can lose prime if not run for an extended period. When they lose prime, the pump may not pick up oil until you help it out a bit. That indicates some pump wear but will work ok once it's primed.
WD40 is not much of a lube for the cylinders, you should use motor oil from a squirt can.

Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Mon Mar 15, 2021 10:38 am

I just pulled the oil filter off and primed the oil pump, put the charged battery on and after a few cranks it fired right up. Thanks for all the help.

Waif
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Re: Cub Loboy hard and slow cranking

Postby Waif » Mon Mar 15, 2021 10:49 am

Pwalker21 wrote:I just pulled the oil filter off and primed the oil pump, put the charged battery on and after a few cranks it fired right up. Thanks for all the help.


Bravo!

W.D. was formulated to displace water. It does that. But is a poor lube.
While on spray can "helper" stuff....Carburetor cleaner has some minor lube quality to it.
Use it instead of the drying effect starting fluid.
But like your Cubs example , if something does not want to start , there is often something that has to change first. VS. keeping on cranking...

Pwalker21
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Re: Cub Loboy hard and slow cranking

Postby Pwalker21 » Mon Mar 15, 2021 10:52 am

Good Info always good to learn something new. Appreciate it.


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