Everything that I have found on readings for compression checks state that 105psi to 120psi is considered factory spec and that they will run down to 90, but getting on the weak side. That is just what I have found on doing searching.
After cleaning and resetting everything the lawn boy runs perfectly but and its a big but every so often it slows down when under load sometimes only somtimes.i know there is no moving parts .i have double checked everything ---any suggestions
Have you checked the exhaust ports and muffler on it. If they are getting plugged up with carbon, you will get a loss in power. When you do get the slight loss, are you on a hill side with the carb aiming up hill? I haven't found a LB that doesn't do that.
After rechecing everything i replaced needle valve ,spring and seat .noticed that the new needle valves do not have rubber tips on them .i wonder is this because rubber disintegrates over time .just wondering.
Now runs like a new lawn boy wow what a struggle .the old parts looked ok to me but guess they were finised after 27 years.