Just did Compression check scared at first

Just check Compression on my 81 kz750 had 120 on all 4

Thought that may be a little low at first.

But engine was cold and I didn't open up the throttle at all.

I am not going to recheck cause done put plugs back in

And everything I read on here says it will go up quite a bit with the throttle open.

Cold and closed throttle you got 120?
That would probably be around 170 if you tested warm with wide open throttle.

I wouldn't bother retesting it either

Well right at 117 to be on the money...dont know why I said 120..cause I got 117 wrote down on the paper down stairs.

It will go up, and with a fully(like, oh my god!!!) charged battery, all spark plugs out, and throttle wide open, you'll get more accurate results. Don't you want to know that your actual compression is now? You gotta be saying to yourself, "I gots-ta know!" I triple-dog dare you to recheck it the way I mentioned, and yes, that's a challenge.

volsrock wrote:

Just check Compression on my 81 kz750 had 120 on all 4

Thought that may be a little low at first.

But engine was cold and I didn't open up the throttle at all.

I am not going to recheck cause done put plugs back in

And everything I read on here says it will go up quite a bit with the throttle open.

I did that test a couple of weeks ago. I think mine went up maybe 30 - 40 psi from spinning with throttle fully closed to fully open. Sounds like yours are right on the money.

Heres the girl

Those numbers are nothing to worry about. Last fall I bought a 750 LTD engine stupidly cheap off ebay because the PO said it smoked when it was in the bike. I hauled it home and tested the compression, with no carbs attached and cold I got 120 psi on all cylinders. Then I noticed that the idiot had it over filled with oil. I took a chance and installed it in a bike I had here, changed the oil and fired it up. Guess what? It runs great and doesn't smoke a bit. From what I remember about what you had posted earlier that bike is a low mileage cherry, just ride it and enjoy it. Don't make yourself crazy worrying about it.