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Compression Release

12K views 19 replies 11 participants last post by  Ironrider 
#1 ·
I was out surfing the net last night and found these EZ Releases from Wimmer Cycles. Has anyone used them? It looks like the easiest compression release without getting into the head. Their sales rep sent me an email that you only need to install one on your rear cylinder.
 
#18 ·
Releases



That would require a cold cranking compression test. To say that a particular compression ratio requires releases is ....well...with all due respect, not enough info. One could have a certain comp. ratio as determined by pistons and combustion chamber volume (and other factors) and depending on cam grind, releases may or may not be needed. Check your ccp.....anything over 185 psi could benefit from some sort of compression releases. ACR's are great....when they work. Manuals are great... when you remember to push the button. Redundant systems cover you best. Hope this helps.
 
#7 ·
I just brought mine in to get compression releases installed. After 12000 miles the little starter is giving out against the 107.

Should have done right away but for whatever reason it wasn't done.
 
#10 ·
JMO, but that looks like a great way to make a simple thing complicated.

If your heads have never been off, you likely don't need CR's. if you mod your motor, have real releases installed then. They're cheaper, and no need for gimmicky "modified" spark plugs required.

Jeff
 
#12 ·
How much does it cost to have manual compression releases put on? That wasn't done to mine when I had it done. They told me it wasn't necessary. I have 10:1 compression.
 
#14 ·
Starters and batteries are cheap who needs CR.
We see it over and over built it but on the cheap leave out the ACR who needs them.
You need them even the 103 factory comes with them HD did not put them in as a selling point there is a reason.
 
#15 ·
Well that's not exactly how it went down. I was told by the builder that I didn't need compression releases because my compression was only 10:1. I know now I should have had em put in, but I tried to take the advice of the guy doing the build. It wasn't a personal friend or anything, in fact I had to hall my bike 10 hrs each way. Now I love the build, just wish I had compression releases.
 
#16 ·
Dynamic compression ratio, or ColdCrankingPressure will be a better indicator of a requirement for comp releases. Anyone who has done a compression test with the throttle closed vs wfo likely understands why. It's harder to know the CCP based on the numbers because CCP is dependent on more factors than a mechanical ratio.. CCP is an indication of how good a pump you've got.

Exaggerated examples:
- An engine with static 10:1 using a cam designed for 12:1 will not need comp releases and should spin over very easily - plus if it had comp releases may not start at all.
- An engine with 10:1 and a cam designed for 8.5:1 (think stock) will likely be unstartable without comp releases because you may not even get the engine turned over.

The statement that a build with 10:1 doesn't require CR's probably had a cam recommendation behind it.
 
#17 ·
Good explanation. I may not need compression releases. My bike starts fine. I just had to replace the starter clutch and compensator and so I was just wondering when i started reading this thread.
 
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