Derby cover bolt options
Seasoned HDF Member
Joined: Sep 2017
Posts: 12,254
Likes: 4,946
From: England
Making sure there is no dirt in the screw head, a properly fitting good quality bit held square to the screw and making sure it is bottomed out before trying to undo the screw all helps.
Even cap head screws have a small chamfer that if the driver isn't fully inserted will round it out.
Even cap head screws have a small chamfer that if the driver isn't fully inserted will round it out.
Last edited by Andy from Sandy; Nov 28, 2023 at 06:57 AM.
Road Master
Joined: Sep 2021
Posts: 759
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From: Under the affluence of incahol.
The other thing is, those screws need barely tightening up. No idea of the torque spec -- who uses a torque wrench on something that small? But just nipped up is all they need to seal if the gasket is good. I had to beat my derby cover out flat with a rubber mallet on a piece of steel plate, the PO, or his mechanic, had so overtightened those screws repeatedly and warped it.
Seasoned HDF Member
Joined: Sep 2017
Posts: 12,254
Likes: 4,946
From: England
Two schools of thought but to the guy who is so heavy handed that he has no clue how tight the screws are a torque wrench would be his saviour. The screws on earlier bikes is around 7ft-lbs. I think on the latest bikes it is a bit less.
Vibration plays a part as they always feel tighter to me when trying to undo them.
Vibration plays a part as they always feel tighter to me when trying to undo them.
Last edited by Andy from Sandy; Nov 28, 2023 at 07:18 AM.
Road Warrior
Joined: Oct 2007
Posts: 1,699
Likes: 3,495
From: Wake Forest, NC
When I bought my Ultra the stock derby bolts were super tight. Even with the correct bit 2 of them stripped. I drilled out the heads and removed the bolt stubs with vice grips. Went back with stainless button head allen. Like others said, those bolts don't need to be very tight, and they are T27. (not T25)
Seasoned HDF Member
Joined: Jun 2015
Posts: 10,287
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From: West Central FL
The original Torx screws work OK if you use the correct size Torx bit on them, which is not included in most standard Torx sets. The next size smaller bit appears to fit but is that bit small and strips the points out of the hole in the screw. You have to buy the correct size Torx bit, but I don't remember what number it is as I bought mine many years ago. And all my standard screws are as good as new.
Seasoned HDF Member
Joined: Apr 2008
Posts: 23,399
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From: Spartan Country, Michigan
One thing to remember is that you are screwing a steel/steel alloy/stainless steel into an aluminum housing. There will be some form of galvanic reaction between two dissimilar metals. A small dab of anti-seize will help with this. Going back to my old dirt bike days, every engine case had phillips screws. We all had hand impact drivers we used to loosen these screws. I guess we were not smart enough back then to swap the phillips out for a different type of bolt!!! But.... I have used my impact driver to loosen tight screws/bolts on my current bikes!
Use what you wish, just use the proper wrench/socket to remove. Keep threads clean. Use anti-seize on dissimilar metals, and don't over torque!! My advice for the day!!!
Use what you wish, just use the proper wrench/socket to remove. Keep threads clean. Use anti-seize on dissimilar metals, and don't over torque!! My advice for the day!!!
Advanced
Joined: May 2012
Posts: 89
Likes: 28
From: NC
25-35 in lbs for the derby cover screws according to the service manual for
my 2023 fatboy..........
my 2023 fatboy..........
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Club Member
Joined: Apr 2016
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From: Inland NW
The other thing is, those screws need barely tightening up. No idea of the torque spec -- who uses a torque wrench on something that small? But just nipped up is all they need to seal if the gasket is good. I had to beat my derby cover out flat with a rubber mallet on a piece of steel plate, the PO, or his mechanic, had so overtightened those screws repeatedly and warped it.
I have had mine out countless times. At least 30 I would guess. They look like new.
Long time mechanic here, and I manage 26 of them currently, so I have seen the mistake with torx head fasteners quite often. I just went through this with a young tech recently, where he rounded out 8 bolts that needed a T27 bit used, and all he had was a T-25 in his set.
He said, "that was what I had in my set, I did not know there were others..."
