2007 Rxp 215 Rebuild Questions

[RxMill00]

Whats going on ! I recently bought 2 Rxp's for less than the price of one knowing 1 of them needed work..

Went out yesterday to start doing some tests and ran a compression test

I was told by the owner that the 1st cylinder had low compression but this is what I found out

Cylinder 1# - 90-95psi
Cylinder 2# - 90-95psi
Cylinder 3# - 60 psi

Decided to put a capful of oil down Cylinder 3# and it maybe moved up 5 lbs of pressure

Just wondering where you guys would start?
What are your thoughts

-rings?
Valves?

Going to start slowly taking her apart , would love the Input!!

 

[ski-d00]

I'd start by taking the head off and you will have most of your answers, or just pull the motor. I'd guess rings are stuck on #3.

 

[RxMill00]

I'd start by taking the head off and you will have most of your answers, or just pull the motor. I'd guess rings are stuck on #3.

Thanks for your input, don't you agree the other 2 cylinders are also low on compression as well?

 

[ski-d00]

Yes, they are low. Check your other rxp's compression for comparison.

 

[RxMill00]

Yes will for sure when I get up to the cabin tomorrow and check the one in the water that runs

 

[AircraftDoc]

The rxp supercharged engine compression is set for 140 psi. Non supercharged 180 psi.
Around 125 to 140 is good. 60 and 90 not so much.