Rear belt alignment question
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Cruiser
Joined: Jan 2011
Posts: 202
Likes: 2
Rear belt alignment question
I have a 1991 FLT which has never been wrecked. I know how to center rear belt on rear wheel pulley with axle adjusters, however to get the belt centered the rear wheel is some out of alignment. When I adjust rear axle parallel with swingarm pivot bolt per HD factory manual, the belt runs against outer flange of rear wheel pulley. Is there any written reference by HD (not the dealer says it should run against the outer flange of the pulley) which says the belt should run against outer flange of rear wheel pulley or should it run a certain distance from the outer flange of the pulley. Is it typical that the rear wheel has to be minimally out of alignment for the belt to run in the center of the pulley. Any opinions. Thanks!!
Cruiser
Joined: Dec 2010
Posts: 110
Likes: 1
From: central NC
You could check it using the string technique. It will tell if you are off center or misaligned. I don't even bother with swingarm marks or measuring. I just use the string if I ever have to move the axle for any reason. Here is one of the many videos on the technique.
http://www.youtube.com/watch?v=RBxK-OQ--fg
http://www.youtube.com/watch?v=RBxK-OQ--fg
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
I have a 1990 FLHS and discovered a different way to check alignment, when I installed a 140/90 rear tyre. It came pretty close to the belt.
With the wheel out of the bike I looked down the side of the wheel, lined the top and bottom edges of the tyre and measured the distance to the track of the belt on the pulley. That was 3/16" for my tyre, but will be a little more for a stock size MT tyre.
With the wheel in my bike I used a 3/16" allen key as a feeler guage between tyre and belt, to align the rear wheel. That sets the wheel true relative to the belt and it runs fine. I then checked alignment using the string method and it was as true as matters!
With the wheel out of the bike I looked down the side of the wheel, lined the top and bottom edges of the tyre and measured the distance to the track of the belt on the pulley. That was 3/16" for my tyre, but will be a little more for a stock size MT tyre.
With the wheel in my bike I used a 3/16" allen key as a feeler guage between tyre and belt, to align the rear wheel. That sets the wheel true relative to the belt and it runs fine. I then checked alignment using the string method and it was as true as matters!
Seasoned HDF Member
Joined: Jun 2010
Posts: 9,324
Likes: 3,869
From: Upstate New York
My belt has always run against the outer side of the flange when running forward, and when I back the bike up, the belt shifts to the opposite side, and rubs against the inner flange. I believe this is by design, as the front pulley has no inner flange at all.
The way the pulleys are made, they are slightly larger in diameter toward the outside, as they are extruded (forged), and need a bit of draft to allow removal from the die. Flat belts will always run toward the larger diameter of a pulley.
Old time machinery that used flat belts always had pulleys that had a slight "crown" at the center. this was how flat belts would run on pulleys with no flanges, as the belt will seek the high point of the pulley. The Harley belt, despite having "teeth", essentially behaves as a flat belt as it interacts with the pulleys.
The way the pulleys are made, they are slightly larger in diameter toward the outside, as they are extruded (forged), and need a bit of draft to allow removal from the die. Flat belts will always run toward the larger diameter of a pulley.
Old time machinery that used flat belts always had pulleys that had a slight "crown" at the center. this was how flat belts would run on pulleys with no flanges, as the belt will seek the high point of the pulley. The Harley belt, despite having "teeth", essentially behaves as a flat belt as it interacts with the pulleys.
Cruiser
Joined: Jan 2011
Posts: 127
Likes: 0
From: Poland, EU
String method is good but not very accurate. Using two wooden beams is much better.
If You can`t get it aligned You should check engine alignment in the frame. If You loosen the main, front engine mounting bolt and two smaller, rubber mount-to-frame bolts then You can move whole unit a bit to the left or right.
If You can`t get it aligned You should check engine alignment in the frame. If You loosen the main, front engine mounting bolt and two smaller, rubber mount-to-frame bolts then You can move whole unit a bit to the left or right.
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Cruiser
Joined: Jan 2011
Posts: 202
Likes: 2
I appreciate the answers. With my wheel aligned, I have .008 inch clearance between the belt and the outer flange of the rear wheel pulley. It just seems too close, because I know if the belt runs against the pulley it will run hot. I have always heard Harley designed the belts to run against outer flange of pulley, however have never found were they said it.
Stellar HDF Member
Joined: May 2009
Posts: 2,856
Likes: 127
From: Middle of Kansas
I just align my rear wheel so that the belt runs in the middle of the rear pulley when turning the wheel forward. Never had a problem doing it this way. I have measured the distance on both sides from the swing arm bolts to the axle center, and it always comes out within a 1/32" or so.
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Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
Set your wheel so that it's straight in the frame. This is important as you want the bike to go straight when you accelerate and brake. This is important as it will make your tires last a little longer and may save your life in a panic stop.
You can watch a bike on the dyno with a chain. The chain will go back and forth "searching" for where it wants to run, belts do the same. In closing I want to stress again, get the tire/wheel straight and the belt will take care of itself. Hope this helps.
You can watch a bike on the dyno with a chain. The chain will go back and forth "searching" for where it wants to run, belts do the same. In closing I want to stress again, get the tire/wheel straight and the belt will take care of itself. Hope this helps.
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