Home › Forum › Ask A Member › 1972 Johnson 2hp – low speed and idle problem › Re: 1972 Johnson 2hp – low speed and idle problem
I have never done a compression test on one of these 2hps, but others have reported much higher compression readings, like 115PSI. Any signs of overheating? Have you had the cylinder head/exhaust cover off? Please don’t rip it apart based on my questioning though, hopefully the problem is a much simpler one like others have described.
I will just emphasize what others have said so far. Make sure the carb butterfly is closing fully, and the throttle shaft is not jammed/corroded. The only way to do this is to remove the carb and look at the butterfly while manually opening the butterfly slightly, then releasing it. The butterfly should snap closed on its own, without having to “help it”. Have a look at the throttle plate as well, does it look like someone has been at the screw/removed it before?
I agree with Fleetwin, compression on those little motor need to 100psi or greater to idle at low range. You maybe only able to run at higher speed due to low compression.
I got one off eBay about 5 yrs back for real cheap. Compression was 90psi. It would not idle well. I used some Seafoam in the fuel mix while running and it decarboned it. It jump up to 115psi. I was lucky it was just carbon causing poor ring sealing.
I sold it a year ago on eBay for about $300. I would always add Seafoam to the fuel mix and it kept it decarboned and the highest psi I got on that motor was 118. Seafoam will not improve compression if the rings and cylinders are worn from a lot of use or poor fuel oil ratio.
A higher fuel oil ratio like 24:1 might improve ring sealing and get a slightly better psi for lower idling.
Here is video of 1972 2hp Johnson I sold on eBay. Yeah I know I talk too much in the video.
Hope this helps some. Cheers!
David T.