Author Topic: Compression test  (Read 8371 times)

Athis

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Compression test
« on: March 07, 2013, 04:02:50 PM »
Ok, so I did a compression test on two of our Ody's and the results concerned me a little. Most of what I've read here on the forum suggests the compression should be right around 120.  I took pictures and video for you guys to check out. Need advice on what I should do before we just go off riding these things.

Ody Number 1


And this is how it sounds when it runs
http://www.youtube.com/watch?v=yhDYIHDDwxE

Ody Number 2


And this is how it sounds when it runs.

http://www.youtube.com/watch?v=HX9nKES_lSA



Athis

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Re: Compression test
« Reply #1 on: March 07, 2013, 07:07:24 PM »
I posted this same question on another site. One guy asked me if I held the throttle wide open. I did not.
Tomorrow morning I'll try it again, this time holding the throttle open as he suggested and see if it changes the readings.

LiveWire

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Re: Compression test
« Reply #2 on: March 08, 2013, 05:35:38 AM »
The throttle not being open is a problem for the test, but that low, I would expect it to still be too low with the throttle open.

odypilots

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Re: Compression test
« Reply #3 on: March 08, 2013, 06:29:12 AM »
Yeah, in my experience holding the throttle open raises the reading about ten pounds. It's time for a least rings.
The usual 'my two cents' disclaimer applies. :)

Athis

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Re: Compression test
« Reply #4 on: March 08, 2013, 10:49:49 AM »
Looks like that may be the case. I'm gonna test it one more time after returning the gauge for another since it tested a little low....5-10 lbs. If I get the same readings after that...I'm gonna pull the engine out for inspection before we ride em.

Athis

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Re: Compression test
« Reply #5 on: March 08, 2013, 02:06:00 PM »
Okay....found the issue. The Harbor Freight U.S General gauges are junk.

So I went back to Harbor freight and exchanged the tester. Came back home....ran the test again....and got the same results as previously posted.
My brother-in-law ( who has an Odyssey) heard of what I was doing and decided to come over with a compression gauge he bought at O'Reilly auto parts.
He paid $50 for his and I paid $20 for mine.

Here's the comparisons of the 2 gauges

[size=150]Ody#1[/size]
Harbor Freight Gauge 


[size=150]Ody#1[/size]
IEC O'Reilly auto parts Gauge



[size=150]Ody#2[/size]
Harbor Freight Gauge 


[size=150]Ody#2[/size]
IEC O'Reilly auto parts Gauge


There is a HUGE difference between the accuracy of these 2 gauges! Yet from the outside the look identical for all intended purposes.
The gauge on the left is the IEC O'Reilly auto parts Gauge and on the right the Harbor Freight Gauge.
And to think I was ready to pull the engine out......valuable lesson learned here. I didn't think there could be such a huge difference in terms of accuracy in something as simple as a gauge.
I certainly hope this helps some people out in the future and saves them from potential unnecessary work and head aches.

Thank you all for your responses and help, it is greatly appreciated. :)

odypilots

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Re: Compression test
« Reply #6 on: March 08, 2013, 03:46:20 PM »
I have never seen such a big variance, either. I'm glad you checked further. ;D
The usual 'my two cents' disclaimer applies. :)

hoodlum

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Re: Compression test
« Reply #7 on: March 08, 2013, 04:26:59 PM »
Are these last readings with the throttle open? If so, they still seem a little low....Especially the 120psi reading....
Hoodlum

Athis

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Re: Compression test
« Reply #8 on: March 08, 2013, 05:01:02 PM »
Me too!

The 120 reading picture was actually 125ish. I took the picture like 5 minutes after I started the engine with throttle open to get the reading. So withing a 5 minute interval I lost around 3-5 lbs.
I suppose the loss could be in the engine and or the gauges fittings.

Do you think 125 is dangerous to run with?

odypilots

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Re: Compression test
« Reply #9 on: March 09, 2013, 04:18:58 AM »
I would run them with those readings if I was confident they're accurate.
The usual 'my two cents' disclaimer applies. :)

hoodlum

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Re: Compression test
« Reply #10 on: March 09, 2013, 05:27:03 AM »
Me too!

The 120 reading picture was actually 125ish. I took the picture like 5 minutes after I started the engine with throttle open to get the reading. So withing a 5 minute interval I lost around 3-5 lbs.
I suppose the loss could be in the engine and or the gauges fittings

Do you think 125 is dangerous to run with?

No, it's not dangerous...As long as it starts easy and idles ok, which are the first things to go with compression loss, I would run the crap out of it....
Hoodlum

Athis

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Re: Compression test
« Reply #11 on: March 09, 2013, 09:52:11 AM »
Ok cool, gonna take em out to day for a spin.
Thanks Hood! :D