Topic: Compression test results question

[SDmtnbkr]

So I borrowed a compression tester from a friend and tested my new (to me) CB750 K5 last night. I really wanted to rebuild the motor for the education and experience, but these numbers are too good to tear it down. I don't wanna mess with a good thing ....right?

Cyl 1. 165 psi
Cyl 2. 153 psi
Cyl 3. 164 psi
Cyl 4. 165 psi

This is warmed up with NO oil added to the cylinders, and all numbers were done two separate times. I kinda figured it would be good because it feels really strong, but this is great! The previous owner must have rebuilt this thing recently, or is this common for a 12k mile bike?

[Steve_K]

I believe having similar psi is good.  If it is new to you, I would ride her for awhile.  I would suggest checking the value clearances to be sure they are in order. 
My 750 had much lower readings, but it had been sitting for a while.  After a tune up  with fresh oil and riding it for several hundred miles, I got 145 psi plus or minus 4 over the 4 cylinders.  The forum has spoken about differences if compression testers. 
I say you are good.  Ride her and see how it goes.
Steve

[b52bombardier1]

I'm sitting at 125 psi on my still dead bike that will get its carbs re-mounted tomorrow and I'm happy with that number - no teardown for me.  Hopefully, my numbers will go up a little after it gets some run time that it has not seen since the late 70's.

Rick 

[SDmtnbkr]

I believe having similar psi is good.  If it is new to you, I would ride her for awhile.  I would suggest checking the value clearances to be sure they are in order. 
My 750 had much lower readings, but it had been sitting for a while.  After a tune up  with fresh oil and riding it for several hundred miles, I got 145 psi plus or minus 4 over the 4 cylinders.  The forum has spoken about differences if compression testers. 
I say you are good.  Ride her and see how it goes.
Steve

Yeah I definitely agree about differences, I used two different testers to verify. One was exactly 10psi lower across the board but would not hold the pressure in the gauge that well and would bleed out a little right after the test. So I didn't trust it all that much. The one that gave me the higher numbers was tested by the owner with his compressor to verify, so I trusted that one more.

[carnivorous chicken]

Ride dat bike.

[PeWe]

compression must be OK.... If engine smoke oil different thing.