Cub motor problems

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Cub motor problems

Postby cwells » Sat Apr 16, 2016 7:26 pm

New motor with about 15 hours on it will not start. It is getting fuel and magneto is producing strong spark. I checked the compression with a gage. # 1 cylinder is zero and # 4 is 15 pounds. I did not check cylinders 2 and 3 because the hood is still in place. Valves are not stuck. Motor has always started hard since overhaul. I have to use 12 volts direct on start to spin fast and occasionally a shot of starting fluid in cold weather. I also put brand new fuel in tank.

Puzzled on the compression problems.

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Re: Cub motor problems

Postby Eugene » Sat Apr 16, 2016 9:00 pm

Remove the valve cover and check the valve stem/tappet gap and valve action.

If it's not valves stuck open, which is unlikely, then you have to remove the head. Check the head gasket for signs of compression leaks.
I have an excuse. CRS.

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John *.?-!.* cub owner
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Re: Cub motor problems

Postby John *.?-!.* cub owner » Sat Apr 16, 2016 9:14 pm

any chance the exhaust or intake are plugged?
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