Cranking compersion figures

[posplayr]

Hey, there are some great pics in that last link. Here is a picture of where i my girl freind at the time took me for my birthday party (25th) . Can't say exactly what the prize was; but you might be able to imagine. She was a Jazzercize teacher.

See pics of the seven falls; we were also doing some compression testing


http://www.google.com/imgres?imgurl=...ed=0CBAQ9QEwAw

[49er]

I don't think that's enough carbon buildup to cause that much jump in compression numbers. Are you sure your guage is any good?

My thoughts too.

That little formula 9.5 -1 = 175 psi, so 10.25-1 = 190 psi isn't what happens in real life rebuilds. Too many variables happen that affect cylinder filling.

I read that link and found that those compressions ranged from 180 -205 psi on the first test and on a cold engine. When it warmed up, you would probably have seen another 20 psi.

Just notice your last post but haven't opened it yet. Are you sure that it wasn't your blood pressure that high on that day??

[posplayr]

My thoughts too.

That little formula 9.5 -1 = 175 psi, so 10.25-1 = 190 psi isn't what happens in real life rebuilds. Too many variables happen that affect cylinder filling.

I read that link and found that those compressions ranged from 180 -205 psi on the first test and on a cold engine. When it warmed up, you would probably have seen another 20 psi.

Just notice your last post but haven't opened it yet. Are you sure that it wasn't your blood pressure that high on that day??

Will do a quick check yet again on my compressor tonite; however to reiterate the same gauge (which was purchased new 1.5 years ago) and I think I may have even double checked with my old gauge measured:

145-165 psi on a well running GS750EX
135-145 psi (if I recall ) on the banana motor Bill has in bike now.
and was as high as 205 psi on my old stock motor.

I would guess the same gauge might come in at 180'ish psi on my 1166?

[49er]

Will do a quick check yet again on my compressor tonite; however to reiterate the same gauge (which was purchased new 1.5 years ago) and I think I may have even double checked with my old gauge measured:

145-165 psi on a well running GS750EX
135-145 psi (if I recall ) on the banana motor Bill has in bike now.
and was as high as 205 psi on my old stock motor.

I would guess the same gauge might come in at 180'ish psi on my 1166?

Don't be disappointed if it's not that high (180). IMO, the greater cam duration and valve overlap, coupled with the increased cross section area through the 4 valves (compared to 2 valves) will hurt the cranking compression figures. But, were you able to check both compression figures at 5000 rpm, the 4 valve engine would be well ahead.

[posplayr]

OK Check out the compresor with 5 seperate guages on it. Turns out there is anout 10-15 PSI variance in the cheap Harbor freight guages, but the two compression testes are within 5 PSI at 90 psi (the limit on my compressor).

The Purple cased guage is the one I used.

Here is the same pic of the banna bike after I had bought it.

[posplayr]

Here is the reading from Bills Banana off of two different cylinders. Reads 210 psi. This was stone cold and not run in probably 3-5 years.

Well I check the original head from the ED and it was stock with the same height as another ESD head I have.

If anything this guage shown is reading low compared to the other three on the compressor and it is the same as the other compression tester guage. Is is hard to believe it has a 50% scale factor error by the time it reaches 210 psi indicated .

Anybody got a phone number so I call NIST.

The way I do the test is to repeatably crank till the psi hit a max with the throttle open while injecting starter fluid with a lit match







Gottch no starter fluid.

[49er]

Here is the reading from Bills Banana off of two different cylinders. Reads 210 psi. This was stone cold and not run in probably 3-5 years.

Well I check the original head from the ED and it was stock with the same height as another ESD head I have.

If anything this guage shown is reading low compared to the other three on the compressor and it is the same as the other compression tester guage. Is is hard to believe it has a 50% scale factor error by the time it reaches 210 psi indicated .

Anybody got a phone number so I call NIST.

The way I do the test is to repeatably crank till the psi hit a max with the throttle open while injecting starter fluid with a lit match







Gottch no starter fluid.

When did you do this test on Bill's Banana motor? He told me a couple of days ago that it was a good runner, but definitely not stock. Doesn't sound like an engine that hasn't run for 3-5 years to me.

[chef1366]

I'll check the compression today to end the speculation.

[49er]

I'll check the compression today to end the speculation.

Hey Bill, it's not necessary. By the way, who owns the Banana, posplayr or you?

[chef1366]

Hey Bill, it's not necessary. By the way, who owns the Banana, posplayr or you?

I own it but he bought it for me and stored it at his house for awhile. Now it's at Kris V's house getting ready to race.

[posplayr]

I'll check the compression today to end the speculation.

Bill unless u plan to remove the rockers, u will not b able 2 reproduce the compression test

[49er]

Bill unless u plan to remove the rockers, u will not b able 2 reproduce the compression test

Ha Ha, nice to see amongst all the Bull Sh!t, there's still time for a sense of humour.