1975 Cub valves

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Jamesk
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1975 International Cub

1975 Cub valves

Postby Jamesk » Mon Aug 27, 2018 9:41 pm

The past two days I have taken the cub for a run around the block. Both times after about a half mile the engine starts tapping and loses power. Both times I have stopped the engine and let it cool for 15-20 minutes restart it and drive a half mile back to the house. What could potentially be causing the trouble. Neither time have I thought to look at the oil pressure gauge when this happened. This engine was rebuilt by a engine rebuild company that has rebuilt many Cubs in the past. I think it’s the pump and I hate to have to run the engine again so that I can look at the guage for pressure drop. I would appreciate anyone’s thoughts as to the probable cause. By the way the engine runs really well until it stars tapping and loses power.

Thanks in advance for your thoughts.
JK

Jamesk
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Tractors Owned: 1963 John Deere 4010
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1975 International Cub

Re: 1975 Cub valves

Postby Jamesk » Mon Aug 27, 2018 9:53 pm

I did read a post from back in 2010 by Clark Thompson stating that the cubs were not designed to use multi viscosity oil in the crank case. I put 10W40 in it. Could this have something to do with a lose of pressure???

Thanks,
JK

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Re: 1975 Cub valves

Postby Eugene » Mon Aug 27, 2018 10:02 pm

Engine dying after 15 or 20 minutes, then restarting after cool down, typical faulty ignition coil.

Start up the cold engine, watch the oil pressure gauge, If the gauge starts to show pressure after 5 or so seconds. Good to go.

The 10W40 engine oil won't hurt anything, should be fine.
I have an excuse. CRS.

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Glen
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Re: 1975 Cub valves

Postby Glen » Mon Aug 27, 2018 10:40 pm

Hi,
You will probably need to run it again, and check the oil pressure often.

If the oil pressure stays normal, and it makes the tapping noise after it warms up some, it could be a valve is too tight in the guide, and it sticks open when it gets hot. That would make it lose power, running on 3 cylinders.

I don't know if they replaced the valves or valve guides. The ID of the guides needs checking after they are installed in the engine.
If too small, they need reaming before putting the valve springs and keepers on.

Jamesk
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Tractors Owned: 1963 John Deere 4010
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1975 International Cub

Re: 1975 Cub valves

Postby Jamesk » Mon Aug 27, 2018 10:46 pm

Coil was my first though due to it getting so hot. I replaced the original coil with a coil without a resistor. You could fry an egg on it. Actually got warm with just the ignition key on. So I replaced with correct coil today. And it did the same thing. Starts with a slight tap and within a few seconds it gets pretty loud and sluggish. I guess I’ll have to run it again and watch the oil gauge.

Thanks,
JK

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Re: 1975 Cub valves

Postby Jamesk » Mon Aug 27, 2018 11:13 pm

Thanks Glen. I’ll check with the rebuilder tomorrow.

JK

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Re: 1975 Cub valves

Postby Glen » Tue Aug 28, 2018 1:03 am

Hi,
You didn't say in your first post that the coil was getting hot, or that the engine stopped on it's own.

"Both times after about a half mile the engine starts tapping and loses power. Both times I have stopped the engine and let it cool for 15-20 minutes restart it and drive a half mile back to the house."

It sounded like you wrote that you shut off the engine, to let it cool down. That's why I wrote about the valves.
The ignition timing being set wrong can cause knocking too. If the oil pressure stays up, you could check the timing with a timing light.

Jamesk
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Re: 1975 Cub valves

Postby Jamesk » Tue Aug 28, 2018 6:17 am

Yes sir, I did cut the engine off when the tapping started. And the coil was an issue from the very first day I wired it. I noticed the coil was getting hot with just the key on ( engine not running). So I changed it out yesterday hoping that was the problem. I’ll check the timing with timing light. Sure hope that’s the problem. I did set the timing with th lights few weeks ago. Just doesn’t make since, engine runs so go and all the sudden it starts tapping. I’ll check the timing again and run it while watching the oil pressure. Thanks very much for your help. Sure hate to have to tear this thing back apart. Maybe I want have to.

JK

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Re: 1975 Cub valves

Postby staninlowerAL » Tue Aug 28, 2018 6:31 am

You are probably dealing with two different problems, coil getting hot from the first day you wired it--look at the components and the way you have it wired. I can't think of anything that tapping in the engine would have anything to do with the coil getting hot but then there's a lot I don't know. :roll:

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Re: 1975 Cub valves

Postby BIGHOSS » Tue Aug 28, 2018 10:07 am

Hey James. How is your coolant level. If an engine gets really overheated strange noises can come from it. Just a thought.
"Courage is being scared to death-but saddling up anyway".......John Wayne

Jamesk
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Tractors Owned: 1963 John Deere 4010
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Re: 1975 Cub valves

Postby Jamesk » Tue Aug 28, 2018 10:13 am

Good Morning Ron,

I filled the radiator with coolant and water (50/50) and it did over flow until the level settled down. You can see the coolant in the radiator when the cap is removed. So a think it okay.

JK

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Re: 1975 Cub valves

Postby mozer71 » Tue Aug 28, 2018 10:58 am

LOL . Well Stan, if there is a lot you don't know then I may be a moron:) However, those super hot coils may indicate some errant ground coming out of the distributor. The isolated contact may be losing its insulation when heated. The condenser might be breaking down after charge. That puts a steady ground to the coil primary winding and that is only supposed to be an interrupted, charged pulse. So there is that which would overheat the coil. This also effects dwell and that effects running timing. So weak spark and retarded timing perhaps?

staninlowerAL
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Re: 1975 Cub valves

Postby staninlowerAL » Tue Aug 28, 2018 11:36 am

Maybe, but this I'm sure about: current flow to ground produces heat. As long as there is no ground there is no heat, that's why I suggested checking the points which obviously grounds the circuit when the points are closed.

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Re: 1975 Cub valves

Postby mozer71 » Tue Aug 28, 2018 12:05 pm

Yes I missed that but there is a capacitor. I think we are both looking at the distributor.

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Re: 1975 Cub valves

Postby mozer71 » Tue Aug 28, 2018 12:24 pm

Jamesk. This is just interesting and we want it to work.


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