How Much Power Should a Cub Have?

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ricky racer
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Re: How Much Power Should a Cub Have?

Postby ricky racer » Wed May 23, 2018 4:33 pm

Wet compression test. You'll know what you've got after that.
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Re: How Much Power Should a Cub Have?

Postby Matt Kirsch » Thu May 24, 2018 1:01 pm

90PSI isn't great, but good enough for plowing and most things, except heavy mowing.

Only thing that has a slim chance of improving compression is a valve adjustment.

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Re: How Much Power Should a Cub Have?

Postby jpate831 » Mon May 28, 2018 7:16 pm

I did the wet compression test. Here are the results:

Cylinder Dry Wet
1 90 105
2 90 105
3 90 105
4 80 115

I guess #4 is the one that surprised me the most. Any interpretations? Is it worth a valve adjustment, or do I need pistons and rings?

Thanks.

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Re: How Much Power Should a Cub Have?

Postby Eugene » Mon May 28, 2018 7:33 pm

I would go with a complete tune up. Your dry compression tests were not fantastic. However, when the engine is running the compression will be higher.

With those dry compression figures, I would operate the engine for several more years before I considered an overhaul.

I operated a Cub with 70 psi dry, for a couple of years before I replaced the engine. Actually, the Cub started fine and mowed well with the low figures.
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jpate831
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Re: How Much Power Should a Cub Have?

Postby jpate831 » Tue May 29, 2018 7:08 pm

Today I decided to adjust the valves. They were a little tight with the .013 gauge, so I adjusted both on each cylinder. After the adjustment I did another dry compression test. Two of the cylinders, including the lowest one, picked up another 10 psi. One stayed the same, and one of them tested 10 psi lower. I haven't figured that one out yet. Maybe it was a bad test. I'll probably test that one again just to be sure.

The tractor seemed to have a little more pep on the test drive afterwards. I horsed around with it a little, and it seemed to do a better under a load. I'm pleased with the improvement, but I'm open to any other suggestions anyone has.

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Re: How Much Power Should a Cub Have?

Postby Bob McCarty » Tue May 29, 2018 9:30 pm

You might want to pick up a can of Seafoam and add to the gas and oil per the can directions. It will help remove any carbon deposits.
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Re: How Much Power Should a Cub Have?

Postby Waif » Wed May 30, 2018 9:24 am

jpate831 wrote:Today I decided to adjust the valves. They were a little tight with the .013 gauge, so I adjusted both on each cylinder. After the adjustment I did another dry compression test. Two of the cylinders, including the lowest one, picked up another 10 psi. One stayed the same, and one of them tested 10 psi lower. I haven't figured that one out yet. Maybe it was a bad test. I'll probably test that one again just to be sure.

The tractor seemed to have a little more pep on the test drive afterwards. I horsed around with it a little, and it seemed to do a better under a load. I'm pleased with the improvement, but I'm open to any other suggestions anyone has.



You might double check all linkage from carb to governor.
I have a lag in response when load on blades is increased. Not so bad when encountering a ten pound rock yesterday ,but I did bog out in tall grass a couple times when too slow raising the deck when r.p.m.' s fell off.
Time to check and lube spindle again and check for debris below deck. A feed bag tie was wrapped briefly and besides affecting balance ,also cost precious blade r.p.m.' s till shed after a few yards.

I'm running brush hog blades to cut high grass so am adding much resistance. A narrow swath trumps a full one or else cut it twice.

Full power in first gear. Deck raised a bit in heavy stuff. We both still had our tongues hangin out a couple times in the heat.


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