1989 Johnson GT200 Compression

[TimTJR]

What compression reading should I get on this engine? Model: J200STLCEB. I have been browsing online and can't find any solid info. I checked the compression on all cylinders with all the plugs removed and they are reading between 71 and 75 PSI. I know compression testers can read different readings so I made a male to male air fitting and tested it with my air compressor just to see if there would be a difference in the gauges. My gauge read 5 psi lower than my air compressor. So I added the 5 psi to each cylinder and that is how I came up with 71-75. How do I know my air compressor gauges are correct? I don't know but this is all I have. Does anyone know what compression reading I should get on this engine as if it were new?

 

[racerone]

Battery and starter condition come into it too.-------What is the your motor doing / not doing ?-----Running issues ?

 

[TimTJR]

It runs okay. Not amazing. I have to give it gas and choke to start it. It's hard to find the sweet spot. Just wondering if I should change out the rings.

 

[racerone]

Not much point in putting new rings in worn out ring grooves !!

 

[TimTJR]

Yea, that is my dilemma. Not sure how much work I want to put into this old motor. If I do anything, I might wait till winter and take it apart to see how bad it really is. I am a machinist, and have worked in tool and die my entire life so I am more than knowledgeable about boring and/or honing. By the way, my battery is brand new, stater is good, spark plugs are new, and primer bulb is new OEM, not a knock-off Wal-Mart purchase. It starts a lot easier after putting new plugs in and replacing the old bulb but still not to my liking. I can't find solid compression data on this engine anywhere.

 

[racerone]

There are many variables so compression data is usually not found in a manual.-----75 psi is low.-------In my opinion it should be in the 90 to 95 range.----Do you have spark on all 6 leads.----They run very well on 5 cylinders.-----Or do a test run on a dynamometer to establish condition of this motor.

 

[TimTJR]

I agree 75 seems low. Some of the forums I read said this motor was designed to run with lower compression but 75 still seems low to me. I will check today if I have spark on all 6. I know I should know this already but I have just been doing a little each day when I get off work.

 

[racerone]

Some of these blocks ( not sure on the 1989 ) have a relief hole in the side of the cylinder.-----Changes compression at low rpm ( cranking ) but at full throttle there is no time for air to bleed off.----So higher compression.

 

[TimTJR]

If that is the case, then my readings are useless.

 

[racerone]

-----Run the motor on a dyno or with a test prop.-----Your local shops can help you I think.

 

[TimTJR]

I checked spark today and all 6 leads do have spark.