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Is my Cub Lo-boy compression too low?

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Bixley

04-30-2005 20:32:21




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I did a compression test on my Lo-boy and got between 70-75 lbs on all cylinders. Is this too low? I put an electronic ignition on it which made it run better but still not good enough. It sounds great until you put any kind of load on it, then it starts spitting and sputtering out of the carb and is weak as a kitten. The carb has been rebuilt, engine timed and valves adjusted. One thing I question is the carb. I had to use two gaskets or else the throttle plate would hit and bind up on the intake manifold so I am not sure if it is the correct one, but it did run good with it at one time. Anyone have any ideas?

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Hermit

05-01-2005 07:24:52




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 Re: Is my Cub Lo-boy compression too low? in reply to Bixley, 04-30-2005 20:32:21  
After your initial compression check, did you squirt some oil into the cylinders and recheck the compression? Did it come up? That's a good indicator if the rings are bad.



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El Toro

05-01-2005 05:41:53




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 Re: Is my Cub Lo-boy compression too low? in reply to Bixley, 04-30-2005 20:32:21  
Low compression could be from the valves not seating plus worn cylinders and rings. Your float level could be a little low too or you have a vacuum leak somewhere to cause the spitting. Hal



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Bixley

05-01-2005 06:33:26




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 Re: Is my Cub Lo-boy compression too low? in reply to El Toro, 05-01-2005 05:41:53  
I've tried all diffrent float levels still the same. It sounds like the low compression is my problem.



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El Toro

05-01-2005 07:19:58




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 Re: Is my Cub Lo-boy compression too low? in reply to Bixley, 05-01-2005 06:33:26  
Squirt some engine oil into the cylinders and recheck the compression. Any increase would
indicate worn cylinders and rings. If there's no change I would do a valve job or have someone to do it. You may need to rebuild the complete engine. Has the engine ever been rebuilt? At one time I saw short blocks for Cubs on here for $300.00, but I think that's been over for some time. That was a bargain at today's prices. Hal

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Bob

04-30-2005 21:03:19




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 Re: Is my Cub Lo-boy compression too low? in reply to Bixley, 04-30-2005 20:32:21  
Compression that low across the board along with the other symptoms makes me wonder if the camshaft timing is off for some reason. Was it running good, and then it started acting up, or has someone had it apart, and it's never been right since?

Of course, it could be badly worn cylinders and rings.



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gene (Missouri)

04-30-2005 20:50:38




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 Re: Is my Cub Lo-boy compression too low? in reply to Bixley, 04-30-2005 20:32:21  
Compression should be around 120 psi new. 70 psi would be on the low end of the scale. Getting close to rebuild time.

Carb question - Doesn't sound like the right carburator.

Gene



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Zenith

05-02-2005 05:15:24




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 Re: Is my Cub Lo-boy compression too low? in reply to gene (Missouri), 04-30-2005 20:50:38  
I think the carb is a Zenith. I've heard other people having problems with the throttle plate hitting the intake manifold, and they were using Zenith carbs.

It's not the "wrong" carb. The late Cubs all had Zeniths.



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