Factory Compression ?

[RonsRanger361V]

Been searching all over the internet with no luck trying to find out what the original factory compression was on a 1989 Yamaha 150 ProV. Wondering if anyone has or knows this information. Reason I am searching is my Ranger has this motor. I am showing 110 PSI across all 6 cylinders. Motor runs smooth and strong with no problems. I would just like to know how far I am from the original compression when the motor was new.
Any help greatly appreciated

Thanks,
Ron

 

[robert graham]

Re: Factory Compression ?

There's no real factory specs on compression, but all readings should be within 10% of each other...sounds like your motor is healthy! A much lower compression reading in one or more cylinders indicates a problem like stuck rings or scored cylinder walls in those cylinders. Good idea to run that Ringfree all the time so carbon don't stick those rings! Good Luck!

 

[RonsRanger361V]

Re: Factory Compression ?

Thanks for the reply. I do add the Ringfree with every fill up. I was just wordering the compression on that motor new out of the box in 1989. Not sure if it was in the 150 range or lower.....higher?

 

[robert graham]

Re: Factory Compression ?

I believe compression readings in the 110PSI to 150PSI, all cylinders within 10%, is considered healthy and normal. There is also a leak-down test that can be of value to evaluate a cylinder's sealing abilities. If your rings are free, clean and seated by proper break-in and your cylinders are smooth, then you should be good to go! Good Luck!