compression releases
Road Captain
Joined: Aug 2011
Posts: 538
Likes: 3
From: Florida
Probably, but it depends on your ccp. Anything up towards 190psi and over and you should have them IMO. My guess is that at 10:1 unless your cam has a pretty large overlap you're gonna be close to 190psi.
theres some calculators on this website that help calculate your static compression and calculate ccp with a library of cams.
http://www.bigboyzcycles.com/calculators.htm
My .02, its like $100 to install them while the heads are off. Just do it. If you try to save a bill and need them down the road youre gonna kick yourself while having to pull the heads again
theres some calculators on this website that help calculate your static compression and calculate ccp with a library of cams.
http://www.bigboyzcycles.com/calculators.htm
My .02, its like $100 to install them while the heads are off. Just do it. If you try to save a bill and need them down the road youre gonna kick yourself while having to pull the heads again
Last edited by Frankenbagger; Jan 31, 2013 at 08:53 AM.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
the compression release is there to allow the motor to get some momentum before compression.
our motors do not have big flywheel mass to store rotational energy so ACRs are a great addition
mike
Road Captain
Joined: Aug 2011
Posts: 565
Likes: 1
From: Pittsburgh
If you dont' want to spend the money on the ACR's then have them install the MCR's like I did. Makes people wonder what your doing reaching down by your spark plugs just before you start your engine. The manuals pop back out from the motors compression once it starts so it's not like you have to reach back down again.
Seasoned HDF Member
Joined: Jan 2011
Posts: 157,462
Likes: 57,017
From: Michigan 15 Minutes East Of Hell
You haven't stated what your build will be ... you might consider S&S Easy Start Cams ... they have a mechanical "compression release" built in and they work quite nicely.
http://www.sscycle.com/feature/featureview.php?s_id=10
http://www.sscycle.com/feature/featureview.php?s_id=10
Stellar HDF Member
Joined: Dec 2009
Posts: 2,561
Likes: 280
From: North Cental Iowa
Why doesn't anybody give a little more o\info when asking a ? Like what cams, what year bike, what size engine, they all make a difference. I'm just picking on you, but so many people give little or no info & expect a reasonable answer. If it's an 07 or newer, yes!
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Road Master
Joined: Oct 2007
Posts: 1,117
Likes: 4
From: Log home in SE Michigan full time. Log cabin in east TN, Smoky Mountians part time
Yes they are worth it. It isnt the starters that are the first to go with the added compression...its the ring gear when the starter kicks out and chips a tooth...or two. Pre 08' you could replace the ring gear easily.....the 08's and later you get to replace the clutch basket too. Ohhhh...next will be the starter drive.
I just built a 107 with Woods TW777 cams...it'll start without pushing in the manual releases...however it cranks a whole lot easier with the buttons pushed in....Doesn't sound near as nasty when the starter drive kicks out either.
I purchased these....http://www.ebay.com/itm/150951860516...84.m1439.l2649
The button on mine were black...sweet they match my bike, lol
They work just like the Jims ones I paid 3x that for on my last build....these aren't rocket science. Save some money buy em'.
I just built a 107 with Woods TW777 cams...it'll start without pushing in the manual releases...however it cranks a whole lot easier with the buttons pushed in....Doesn't sound near as nasty when the starter drive kicks out either.
I purchased these....http://www.ebay.com/itm/150951860516...84.m1439.l2649
The button on mine were black...sweet they match my bike, lol
They work just like the Jims ones I paid 3x that for on my last build....these aren't rocket science. Save some money buy em'.
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Extreme HDF Member
Joined: Nov 2007
Posts: 14,670
Likes: 139
From: East of the Sun, West of the Moon
You haven't stated what your build will be ... you might consider S&S Easy Start Cams ... they have a mechanical "compression release" built in and they work quite nicely.
http://www.sscycle.com/feature/featureview.php?s_id=10
http://www.sscycle.com/feature/featureview.php?s_id=10
Road Captain
Joined: Sep 2012
Posts: 675
Likes: 32
From: Massachusetts
i'm @ about 10.2:1 on my evo, and i had Bean @ BBC in maine put MCR's in my heads.
in the cold: dont need em. spins pretty good (and starts FAST). once shes good and warm though, she definitely cranks a bit easier with them pushed in. (this is with a W6....already debating going bigger and picking up a W8)
i'm @ (calculated) ~ 195psi cranking pressure on the original starter from 1998 (did lose a starter clutch, once, although that was before I bumped the CR to 10.2:1)
in the cold: dont need em. spins pretty good (and starts FAST). once shes good and warm though, she definitely cranks a bit easier with them pushed in. (this is with a W6....already debating going bigger and picking up a W8)
i'm @ (calculated) ~ 195psi cranking pressure on the original starter from 1998 (did lose a starter clutch, once, although that was before I bumped the CR to 10.2:1)