[jet69]

Hey, I bought a cheap arse compression tester from fleabay, I'm getting to variation of 25 psi when using the flexible hose and the push in tube.
Using the push in tube I'm getting 125psi in both cylinders when warmed up and by adding a little oil I'm getting 150psi at sea level.
I'm interested in comments out there, the bike has 38 000km on it.

cheers

 

[belter]

that's fine. i've never tested one with oil in there, but a typical test during service should see 120 - 130. advance the cams and you might see 145.

 

[ducvet]

If I am following you correctly you are getting a variance between two gauges NOT between two cylinders, correct?

If so know that different gauges will read differently, I ran into this recently with my snap on gauges. The gauges have a Schrader core in them and due to other tests I am always moving it around well it wore out so I had my snap on rep get me a new rebuild kit. With the new kit bikes were down on compression , by like 50psi ! I tried all kinds of different rated cores and could easily move the rating up or down.

In the end I bought a new snap on gauge (with new core) and was back to realistic numbers, I tried the new core in my old gauge and it was again matching the new gauge. Lesson learned it is easy to get a false reading so be sure the right core is installed and care less about overall psi as much as variances between cylinders. At least all the testing did help one of my control tests was a 50,000mile m900 on the dyno for a running problem. It made good power but had a hiccup. One cylinder was down 20% over the other and a later leak-down found a burnt exhaust valve.