djohn24 10 #1 Posted September 26, 2015 I recently purchased 416H. Tractor is showing 625hrs. I just did a compression test on the motor. I got 103 on the front cylinder and 110 on the back cylinder. I guess I was expecting the 125 psi's that other people get on these motors, for that amount of hours. Or, am I mistaken? I see that the 16hp Onan is 6.5 to 1 compression ratio v.s. the 18,20,24 hp engines are 7.0 to 1. Forgive me for my lack of knowledge but, according to those ratio's, would'nt the 16hp engine naturally have a lower compression reading? I figure there are some onan guys out there can chime in on this. Thank you, Dennis Share this post Link to post Share on other sites
Ed Kennell 42,109 #2 Posted September 27, 2015 Your logic seems correct to me Dennis. I have one 520, but I am no ONAN expert. Maybe BOOMER the ONAN guru will chime in.Or if you are going to the Steam 0 Rama this week, look up EricJ. I'm sure he can answer any questions. Share this post Link to post Share on other sites
doc724 925 #3 Posted September 27, 2015 I believe the Onan spec is 95-125, so 110 is right in the middle of the range. My P216 with 775 hours was 110. BTW, 6.5:1 compression ratio calculates to 94.3 psi 1 Share this post Link to post Share on other sites
boovuc 1,090 #4 Posted September 27, 2015 Be very VERY thankful you have over 100 PSI compression on the rear cyl of your Onan. Bottom spec is 95 so 110 is excellent.Do your regular preventive maintenance and keep the engine tins and the intake screen clean and your good to go. 2 Share this post Link to post Share on other sites
djohn24 10 #5 Posted September 27, 2015 Thank you men for your input! Sounds like the readings I got are just fine. Ed, I know Eric and I normally go to him for these Onan questions. I try not to bug him all the time and haven't seen him on here lately. I also have dealt with Boomer too. He knows his Onans' I have never been to the Steam O Rama...Off Manor Rd. right? Share this post Link to post Share on other sites
