[sak384]

bought my son an 07 crf150r. Having new top end, valves shimed and adjusted, flywheel weight being installed this week. looking for the baseline compression readings after break-in. i am familiar with 2 stroke procedure is this the same for 4 strokes?

[sak384]

looking for baseline fresh top end compression readings for 07 crf 150r.
Service manual says about 73psig at 600 rpms. How can you gauge 600 rpm from kicking the bike over with a compression gauge on the cylinder. Hmmm this does not sound too complicated anyone....

[Asmith]

With the auto decompressor, you won't see anything higher until you can spin the engine fast enough to defeat it.

Why are you concerned with compression figures on a new top end??

If you are trying to see the quality of the build, do a leakdown test. That'll show you much more info.

[sak384]

Thank you for responding ~. I am no expert.
I am new to 4 strokes but have experienced 2 strokes. There are obvious differences in testing and i am trying to get up speed. I wanted to be able to have a baseline compression reading to know when it's time for a new piston and rings. If i could measure any significant change it may also prevent wasting time trying to jet a bike with worn rings.In my service manual it suggests that poor idle and poor low speed performance can also be a result of a loss of compression. It also suggests to test it. The manual says 73 psi at 6oo rpm's. Unless the bike is running how can this test be done? Can a reading be obtained from kicking it over like a 2stroke with the compression spark plug adapter installed. ? I thought the leak down test was primarily used to test for big end bearing seal leaks.