103" big bore without compression release?
Grand HDF Member
Joined: Jun 2008
Posts: 4,012
Likes: 298
From: Central Fl
When I originally started planning the upgrade to a big bore 95 cu. in., a local HD dealer told me that I didn't need CRs even though the compression would have been bumped up to 10.5:1 using the components they planned to install. I thought it was a little fishy when they told me this. When I ended up settling on an independent engine builder, I asked him why the dealer didn't think I needed CRs. According to him, dealers (and indy shops as well) frequently don't have the capability to machine the heads to accept compression releases OR don't want to take the time to send the heads out to have them machined for the releases. Consequently, a lot of modified engines end up not getting compression releases when in reality they probably should have them. The lesson here is, if your engine is being modified, you may have to insist on having CRs installed even if the engine builder tells you they aren't required.
+1. Dealership said not to worry. 2 yrs later I'm adding SE heads with acr's. No problems at all now.
Road Master
Joined: Dec 2005
Posts: 1,078
Likes: 5
From: Hickory, NC
...Personally before I would put cr's in and run the chance of them ever leaking and causing the engine to run lean (because who checks or changes the seals) I would go with a higher torque starter and always keep my electrical system checked and sealed. Thats me though.
Regardless of whether it results in a rich or lean condition, the leaking CR would need to be replaced. However, you can buy a lot of replacement CRs before it adds up to the cost of installing a higher torque starter.
Tourer
Joined: Jul 2009
Posts: 350
Likes: 0
From: TN
For those of you who do not know the MCR's can and will stick open if not cleaned. But you can manually close them if they do not close automatically (just pull up). Never had one stick after a few revs but one of those things I learned after watching a wrench fire mine up. I just smiled and thought how dumb I was not to think of that. I have ACR's now and not sure what to do if they stick or have some sort of problem. They may be bullet proof I dont know.
Sath
Sath
Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
For those that worry about then sticking i would suggest a few drops of wd 40 or penetrating oil on the cr's at an oil change or before extending riding in foul weather or if you live by any salt water coasts
Road Master
Joined: Dec 2005
Posts: 1,078
Likes: 5
From: Hickory, NC
I would think if you could draw enough air through a stuck CR on the intake stroke to create a lean condition, it would also cause enough compression loss on the compression stroke to prevent the cylinder from firing at all. And, you can't have a lean condition if the cylinder doesn't fire. If anything, I'd think they're be more of a risk of washing the cylinder walls with raw fuel and causing cylinder scoring.
Road Master
Joined: Aug 2010
Posts: 1,152
Likes: 3
From: Central Ohio
This thread is very interesting and timely for me because a week from today I'm having the SE Stage II 103 kit w/255 cams being installed. How much more should I expect to pay if I ask them to add the ACR's?
Thanks,
mikebaby
Thanks,
mikebaby
Last edited by mikebaby; Dec 9, 2011 at 10:44 AM.
Ultimate HDF Member
Joined: Nov 2008
Posts: 6,682
Likes: 12
The ACR's are around $80 retail with the wiring adapter I think. The machine work the heads will need to accept the ACR's will run about $250 from most shops that do them. Another option is manuals releases. They run about $40 for the pair and about $80 to have the machine work done for the heads to accept them.
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Grand HDF Member
Joined: Dec 2007
Posts: 4,999
Likes: 55
From: Bay Area
I would think if you could draw enough air through a stuck CR on the intake stroke to create a lean condition, it would also cause enough compression loss on the compression stroke to prevent the cylinder from firing at all. And, you can't have a lean condition if the cylinder doesn't fire. If anything, I'd think they're be more of a risk of washing the cylinder walls with raw fuel and causing cylinder scoring.
Road Master
Joined: Dec 2005
Posts: 1,078
Likes: 5
From: Hickory, NC
Wasn't really referring to what you said. However, in the case of a leaking seal between the CR and the head, I just don't see how you could draw enough air in to cause a lean condition. The amount of air that would be drawn in through a leaking seal would be so incredibly small compared to the amount of air drawn through the intake I don't think it could possibly be enough to cause a lean enough condition to be of concern.