I did a compression test today and i was wondering what you think. It's a 1990 GSX, here are the numbers from pass side to drivers 145 145 150 153. Just wondering if those are good or not. Thanks

Well, theyre not perfect, but I wouldnt say that they are bad. Definitely good enough. Did you unplug the MPI fuse? They are all within 10 percent of each other which has seemed to be the most important thing to me, and I believe that is still pretty damn in "in spec".

Mine are 150 across the board and my engine has about 30k on it. Looks good.

I thought they were pretty good but thanks for the input. The engine was "supposedly" rebuilt about 30,000 miles ago so the numbers sound like it was then. Thanks

Why do you need to unplug the MPI fuse to do a compression check?

From what I have heard not unplugging the MPI fuse can skew numbers because fuel is going into the cylinder while cranking. You unplug it so it disables the injectors.

It wont screw with your numbers... it will just spray alot of fuel into the cylinders while you keep cranking.

Think about that for a second or two.

It might bump up your numbers I guess but really how much? (or am I wrong) It would bump up becuase the extra juice sitting in the chamber which would keep increasing with every crank?

Oh, now I am on the same page. I just disconnect my injectors for a compression test.