Compression & Leak-down Results - Easy-Start
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Road Warrior
Joined: Nov 2005
Posts: 1,484
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From: Mountain View, California
Compression & Leak-down Results - Easy-Start
Ran compression and leak-down tests on my troubled 100" build (rear cylinder 100 degrees hotter than front w/ 100 careful miles toward break-in).
Leak-down was done with engine warm but not operating temp. 7% in rear cylinder, 5% in front. Since I've seen many reports indicating not much difference cold to hot, I suppose I can call this good?
The compression test was complicated by having S & S Easy Start cams. I got the bike to operating temp (250-degrees), killed the engine, popped the connector off the front injector, inserted the compression tester, started the engine and blipped the throttle a couple of times until the needle stopped climbing and got about 135 PSI. Did the same on the rear and got about 150 PSI.
Keep in mind that during these compression tests, I was not able to hold the throttle open as you normally would, so the results will be lower than if performed without Easy Start cams.
So, any thoughts / opinions about these results?
As usual, thanks in advance!
https://youtu.be/RymriI5MYpE
https://youtu.be/0V0cWlt00XU
Leak-down was done with engine warm but not operating temp. 7% in rear cylinder, 5% in front. Since I've seen many reports indicating not much difference cold to hot, I suppose I can call this good?
The compression test was complicated by having S & S Easy Start cams. I got the bike to operating temp (250-degrees), killed the engine, popped the connector off the front injector, inserted the compression tester, started the engine and blipped the throttle a couple of times until the needle stopped climbing and got about 135 PSI. Did the same on the rear and got about 150 PSI.
Keep in mind that during these compression tests, I was not able to hold the throttle open as you normally would, so the results will be lower than if performed without Easy Start cams.
So, any thoughts / opinions about these results?
As usual, thanks in advance!
https://youtu.be/RymriI5MYpE
https://youtu.be/0V0cWlt00XU
Last edited by Z; Sep 3, 2018 at 01:40 AM.
Thread Starter
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Road Warrior
Joined: Nov 2005
Posts: 1,484
Likes: 82
From: Mountain View, California
While related to thatt thread, placing it there might cause someone with specific experience in Easy Start compression testing to pass over it.
Also, listing it as a new topic will make it more likely for those searching in the future for topics with "leak-down" or "compression test" in the title to benefit from the replies.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,064
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i say you are good to go. street machine leak down above 92% is good to go although higher is better.
the compression is in the 10% diff'l range so you are good to go.
as far as taking a engine running compression, that is exactly how you do it on a diesel and on older gas machines like coopers and such, set the main gas valves and cyl loading while running.
the compression is in the 10% diff'l range so you are good to go.
as far as taking a engine running compression, that is exactly how you do it on a diesel and on older gas machines like coopers and such, set the main gas valves and cyl loading while running.
Thread Starter
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Road Warrior
Joined: Nov 2005
Posts: 1,484
Likes: 82
From: Mountain View, California
Bustert, I think it looks that wsy too.
Anyone have an idea how much lower the compression would be when done this way rather than with the throttle blades wide open?
Anyone have an idea how much lower the compression would be when done this way rather than with the throttle blades wide open?
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,064
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i do not think it to be lower. if you look at it, it would be more averaged out. at crank speeds, rotation would be slower and no back-pressure from downstream. at running rpm, you have downstream pressure effects, compression heating due to higher rpm. i would not expect a large diff'l. if anything probably higher by a tad. another point is that the rings would seal better. running compression on a diesel is higher than cranking.
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Road Warrior
Joined: Nov 2005
Posts: 1,484
Likes: 82
From: Mountain View, California
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Tourer
Joined: Jul 2017
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From: UAE
Did a test on my setup,not with an easy start cam, but with HD Automatic Compression release enabled and disabled.
With ACR enabled I get around 168 PSI, with ACR disabled it's 230 PSI.
With ACR enabled I get around 168 PSI, with ACR disabled it's 230 PSI.
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Thread Starter
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Road Warrior
Joined: Nov 2005
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Likes: 82
From: Mountain View, California
Did you do this at cranking speed or with the engine running?
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