Compression Releases
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Road Master
Joined: Dec 2006
Posts: 1,200
Likes: 3
From: Simpsonville, SC
Compression Releases
I'm doing a 95 build on my Twin Cam, it will have approx. 10:1 compression, and Andrews 54 cams with ported and polished heads. Are compression releases going to be necessary??
Elite HDF Member
Joined: Mar 2006
Posts: 4,722
Likes: 5
From: Biddeford, Maine
It's always a good idea to have them installed when the heads are off, even if you don't think you'll need them..........do it now. Much easier then finding out later that you do need them, and having to tear the motor apart again to have them installed.
Steve
Steve
Outstanding HDF Member
Joined: May 2008
Posts: 2,543
Likes: 19
From: Ashland Ohio
I would say that you will not 'need' them. But.... how much would it be worth for that one hot day, after buying gas with a bunch of friends, and the bike won't start properly?
I would think that $100 now is just too good of a deal to pass up, compared to any trouble later. Have the head porter put them in, like Big Boyz did for me.
And... here is the thought... you may not keep those 54s in there forever and the 'new' cam could really use the releases... but you were too cheap to do it way back when.
I would think that $100 now is just too good of a deal to pass up, compared to any trouble later. Have the head porter put them in, like Big Boyz did for me.
And... here is the thought... you may not keep those 54s in there forever and the 'new' cam could really use the releases... but you were too cheap to do it way back when.
Elite HDF Member
Joined: Apr 2009
Posts: 3,928
Likes: 1
From: Desert S. West
Yep. You'll need them when you stop for gas and try to start it again and get the dreaded compression lock. Don't ask me how I know. 
Hot starts can be very hard on the starter with a higher compression motor. Some people just get more powerful starter then break the jack shaft which could also damage other parts in the primary.
Hot starts can be very hard on the starter with a higher compression motor. Some people just get more powerful starter then break the jack shaft which could also damage other parts in the primary.
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Road Warrior
Joined: Nov 2007
Posts: 1,984
Likes: 7
Couple of things about hot starts.
One came from a suggestion on this site from somebody and this works.
When you start your auto you just turn the switch don't you? You don't wait for it to go thru its pump up routine do you? May not hear it but it does exactly the same, all the same.
Do that with the Harley. Turn the switches and hid the start button right away. Easy start up. Check Engine comes on, but then goes away a few seconds later.
Another for high compression, high lift engins is S&S travel limiters for stock type lifters.
Doesn't let the lifters bleed down far when stopped. Especially troublemsome when hot.
If stock lifters are adjusted stock you can loose 0.100 in. lift at hot start.
One came from a suggestion on this site from somebody and this works.
When you start your auto you just turn the switch don't you? You don't wait for it to go thru its pump up routine do you? May not hear it but it does exactly the same, all the same.
Do that with the Harley. Turn the switches and hid the start button right away. Easy start up. Check Engine comes on, but then goes away a few seconds later.
Another for high compression, high lift engins is S&S travel limiters for stock type lifters.
Doesn't let the lifters bleed down far when stopped. Especially troublemsome when hot.
If stock lifters are adjusted stock you can loose 0.100 in. lift at hot start.
Last edited by Old Gunny; Jan 4, 2010 at 09:57 AM.
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Outstanding HDF Member
Joined: Sep 2007
Posts: 3,352
Likes: 4
From: Augusta, GA
I'm running a 95" with 10.1:1 comp and Andrews 54H cams.
I use the rear comp release religiously, it really helps.
I noted and then was confirmed by my machinist that these fuel injected bikes don't like the front comp release. If I use both front and rear it doesn't start as quickly. The rear cylinder is typically the one causing any problems needing the release.
Good luck and enjoy.
I use the rear comp release religiously, it really helps.
I noted and then was confirmed by my machinist that these fuel injected bikes don't like the front comp release. If I use both front and rear it doesn't start as quickly. The rear cylinder is typically the one causing any problems needing the release.
Good luck and enjoy.