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How much compression should a 5hp Honda CX 160 have. Thanks for an answer. Also what does a 8.0 : 1 compression ratio mean?

It means that the volume of the cylinder/combustion chamber when the piston is at top dead center is 1/8th of the volume it is when the piston is at bottom dead center.

Compression should be 85-121. an 8:1 compression ratio would give you a compression of 116 psi.

cpurvis said:

It means that the volume of the cylinder/combustion chamber when the piston is at top dead center is 1/8th of the volume it is when the piston is at bottom dead center.

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Thanks for answer.

ILENGINE said:

Compression should be 85-121. an 8:1 compression ratio would give you a compression of 116 psi.

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This 5hp Honda engine had O compression when I first checked it. It has OHV so I tried to free it up without taking the head off. I did free it up but had only 20 lbs after that. I took the head off, cleaned and resurfaced the valves and they looked good. I had 70 lbs after that. It runs but not long. I looked at some PDFs but couldn't fine how much compression it should have. Looks like I need at least 85 lbs to run better. Must have a stuck compression ring or oil rings. There is no ring grove on top of the cylinder wall so I don't think the rings would be worn very bad. I will take the piston out when I get time and see whats up. Thanks for the help ILENGINE. You have been a lot of help to me, thanks.

Be careful with compression readings on small engines.
Most have a compression releaase system so you can not get true reading and further more the reading you do get will be dependant upon the valve lash.
So to get a try reading you have to defeat the compression release which on Hondas is near impossible to do.
This is why you will see those who know what they are talking about carrying on about leak down testing to test rings.
As a rule of thumb the engine will need to show 60 to 80 on your gauge to be able to start and thay is taking the compression release into account.

bertsmobile1 said:

Be careful with compression readings on small engines.
Most have a compression releaase system so you can not get true reading and further more the reading you do get will be dependant upon the valve lash.
So to get a try reading you have to defeat the compression release which on Hondas is near impossible to do.
This is why you will see those who know what they are talking about carrying on about leak down testing to test rings.
As a rule of thumb the engine will need to show 60 to 80 on your gauge to be able to start and thay is taking the compression release into account.

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Thanks for answering bertsmobile, you saved me a lot of work. When I was setting the valve clearance I noticed the exhaust do a little dip on the compression stroke and I knew that was the CR but I didn't know it would effect the compression test. With an 8:1 compression ratio and 117 max compression I didn't think I had enough at a 70 reading. But thanks to you it looks like the piston and rings are good. I couldn't feel a ring grove on top of the cylinder wall so I thought the rings were stuck. You saved me a ring job on this engine. I have been getting some very good advice on this forum but you are one of the best if not the best on here. You give me good advice that no one mentions. Thanks so much. Your friend Cambre