What is this?
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Tourer
Joined: Sep 2012
Posts: 311
Likes: 0
From: South Carolina
What is this?
I was looking at my brothers 03 Fatboy today and noticed these rubber capped things next top the spark plugs. What are they and what are they for? I don't think they are on my 06 NT. Thanks!
Stellar HDF Member
Joined: Feb 2011
Posts: 3,048
Likes: 3
From: Central Jersey
compression releases, you should have seen one on both heads.. it means someone may have had the heads bored/ported/polished.. just push each of them down before he starts the bike, and the compression from the piston firing will pop them back up. they take the stress off from the starter having to crank the motor over on big bore engines.
Thread Starter
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Tourer
Joined: Sep 2012
Posts: 311
Likes: 0
From: South Carolina
Well that's cool. They seem to spin like a cap, I don't know if they free spin or the spin off or if it's an adjustment or not. So just push them all the way in before each time he cranks it or just when it's cold?
Now that I know I don't have them on my NT...... I want them!
Now that I know I don't have them on my NT...... I want them!
Seasoned HDF Member
Joined: May 2005
Posts: 10,233
Likes: 9,331
From: Georgia
They are needed in high compression motors especially 10 to 1 and higher. I never needed them when I just had the 95ci motor that came in just under 10 to 1. When you jump up to 10.5 and higher a hot motor benifits from them and a good starter. I say they aren't needed in a lower comp.motor but if you have them use them. You will know the first time you crank it over when hot. I never use them starting my motor cold.
Road Warrior
Joined: Nov 2009
Posts: 1,444
Likes: 1
From: SC
Mesa they are compression releases. Push in before every start is best. Careful not to burn fingers when engine is hot. They are a pain if you're bar hopping with frequent starts. The button on top will spin either way, it's just a shaft with a plunger on the bottom inside the head. Eventually they will start to stick open. Take them out, wipe off any dirt, lubricate the moving parts with a light coat of engine oil, put back in. Careful not to overtighten putting back in. The threads are small and the head is aluminum.
Road Captain
Joined: Jun 2012
Posts: 503
Likes: 9
From: NM
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Grand HDF Member
Joined: Sep 2009
Posts: 4,626
Likes: 98
From: Lake of the Ozarks, Missouri
Every chain saw I own has a compression release but I have to admit I have never seen one on a bike.
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