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5-Ball Bagger Project Bike -- The Infamous Harley Wobble -- Part 2

More Tech Questions than Answers

By Krash Kranzler
5/15/2014


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The Bikernet Baggers 97 FLT project bike in its current state.
The Bikernet Baggers 97 FLT project bike in its current state.

 
Ever since that fateful day when the infamous Harley Wobble bit me in the ass. I have been researching this FLT specific issue. I have reached out to engineers, designers, mechanics, and the aftermarket looking for the solution. All I have ended up with is more questions that seem to have no concrete answers. Below you will find some of the main items that come to the head of the list starting from the front end to the the swingarm as I get ready to order a new frame from Paughco.
 
Front End
 
FLT front fork geometry 101
FLT front fork geometry 101

 
It doesn't seem to come up often in discussion’s of the Harley Wobble but it is one of the major differences between the FLT and Harley-Davidson best handling bike ever produced the FXR and that would be the Rake and Trail. 
 
The FLT has a 26 degree neck angle with 5 degree reversed cast triple trees giving the FLT over 6 inches of trail this makes for a very nimble and controllable bike at slow speeds and what should be a very stable platform at high speeds. 
 
The FXR chassis has a 29 degree rake with 0 to 3 degree standard triple trees giving the FXR 4 inches of trail, by comparing the numbers the FLT should on paper be a much more stable bike at speeds yet almost everyone claims that the FXR far surpasses the handling of the FLT.
 
Stock replacement frame by Paughco
Stock replacement frame by Paughco

Raked FLT frame by Paughco
Raked FLT frame by Paughco

Paughco has all your FLT frame needs or wants covered
Paughco has all your FLT frame needs or wants covered

 
 
Engine mounting
 
Factory style front motor mount and stabilizer link
Factory style front motor mount and stabilizer link

 
The Harley FLT engine is rubbermounted both front and rear with a top link that helps stabilize the engine in the chassis. This helps greatly in keeping the engine vibrations away from the chassis but also allows the engine to move around on the motor mounts causing a potential binding situation at the rear engine/trans/swingarm mount. For more details and a Engineers review of this problem please Click Here: The Infamous Harley Wobble Part 1 as Graham R. Brown has gone into more detail than I need to repeat here. 
 
Upgraded Paughco front motor mount
Upgraded Paughco front motor mount

True-Track Stabilizer link
True-Track Stabilizer link

 
 
The aftermarket industry has many solutions to the lack of a rear stabilizer link to help curb the lateral motion of the engine and this is something Bikernet Baggers will be using to help tame the possibility of another case of the Bagger Wobble.
 
Swingarm
 
Custom Cycle Engineering-- Late Model Swing Arm Retrofit - with Axle
Custom Cycle Engineering-- Late Model Swing Arm Retrofit - with Axle

 
 
The FLT and FXR swingarm mount also does double duty as the Engine/Trans mount by using rubber Cleve Blocs to try to keep everything in line. This allows the swingarm and engine to get out of alignment in certain riding situations and causes a binding that is believed to be one of the major causes of the dreaded Bagger Wobble. Harley changed the design of this system with the latest model FLT chassis by changing the rubber cleve blocs to Spherical bearings that do not allow the twisting movement prevelant in the rubber bushings.
 
Spherical bearing Upgrade kit by Paughco
Spherical bearing Upgrade kit by Paughco

 
As usual the aftermarket has stepped up and many companies make retrofit kits to change the cleve blocs to spherical bearings. 
 
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Maintenance
 
How much of the Bagger Wobble is caused by lack of maintenance is a question I ask a lot as the 97 FLT project bike that was wrecked had 30,000 miles on it when we purchased it and we have no records from its past life.  Was this bike ignored in its past life? 
 
Some of the things I question now are things I could have easily checked but I blissfully ignored as the bike seemed to be in great shape.
 
   1.) Neck bearing preload and condition
   2.) Motor Mounts 
   3.) Cleve blocs
   4.) wheel bearings
   5.) wheel alignment
 
All of these items seemed in fine shape but they all would have had wear after 30,000 miles and does the stacking of wear and tolerances have a responsibility for helping to cause the Bagger Wobble?
 
 I have always like the look of the geometry on these two bikes. Is this a direction I should go? 
 
Conclusion
 
Like I said at the beginning I really have ended this research with even more questions than I started with but I have come up with some of my own ideas for the rebuild of the Bikernet Project Bagger that I want to throw out to the reader for input. 
 
Bikernet Baggers is currently working on ordering a chassis from Paughco. Should we order a stock replacement frame or change the neck angle and trees? My personal opinion is to change the neck angle to 35 degrees with standard offset racked trees to build a touring chopper.
 
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We are also going to be using a rear stabilizer link to calm some of the lateral movement of the engine in the frame, the stabilizer along with swapping out the rubber cleve blocs for the spherical bearings should stop the binding that is prevalent in the factory design.
 
We are looking for input on this build so don’t be afraid to send me an email at: richard@bikernet.com or leave a comment on how best we can build a wobble free bagger.
 
Thanks
Krash Kranzler 
 

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