Need assistance with diagnosing front suspension

[Tactical_Mik]

I've been trying to work through this but have not found the cause and am at a loss at this point.

I have been trying to work out a fast sweeper suspension undulation and my front end in a straight line was bouncing as if the front tire was badly out of balance.  I checked the tire, it was balanced.  Next was the thought that maybe the fork fluid had become too contaminated or aged to dampen properly (09 bike about 22 mo old with 26K on the odo).  I changed the fluid, no joy.  Then I thought (since I only have the capabilities of static balancing the tire) that maybe the tire had become delaminated or something.  I replaced the tire, no joy.  Next, was another fluid change to a different manufacturer, again to no avail.  I've checked and rechecked everything I can think of, including the steering stem adjustment and am now out of brain power.

Any suggestions?

[lather]

Did this start recently?
 I am thinking aero. Any recent changes is that department?

[Tactical_Mik]

Its been going on for about two months but I was scarce on time previously as my SO had to go in for two surgeries.  Have been actively pursueing a fix for about 3 weeks now.

[VirginiaJim]

Tire?

[gPink]

Load change? Trunk mounted and loaded?
Any changes in the rear suspension settings?

[Tactical_Mik]

I checked then replaced the tire just in case.  I haven't changed the carried load since I got it and have made no changes to the suspension settings prior to the onset.  It's a puzzle for sure.

[Jeremy Mitchell]

My bike has some front end "shimmy" out on the interstate when the wind hits my VStream at the right angle.  If I feel that I just drop the windshield all the way down and it goes away.

[Tactical_Mik]

My front end issue isn't side to side but up and down.  In this Kansas heat/wind I always keep my windscreen in the lowest position.  That's the only way to survive the temps. 

[lather]

wheel bearings, axle?

[Tactical_Mik]

I haven't thought to check the wheel bearings.  I just replaced them about 4 thousand miles ago as I wasn't keeping up on the dust seals.  That allowed some debris/water in the left bearing.  I guess I'll add that to the list of things to check.

[jsa]

I would guess that you have crud buildup in the lower forks that is partially blocking the compression damping circuits.  That crud can be pretty hard to remove as long as the cartridge is in place although you could try a strong cleaner and leave it in the forks overnight.  Just make sure the cleaner will not dissolve the rubber gaskets that are on the compression damping piston.

[coastalconnie]

Have you tried re-seating the axle? Before torquing the pinch bolts, have a friend sit on the bike to put some weight on the front wheel while you tighten the four pinch bolts. Doing this while moving the handlebars left to right might also help to re-seat the axle if needed.

[Tactical_Mik]

Not too sure about buildup in the tube although it is a possibility and I will check.  When I changed out the fluid the second time, about 400 miles apart, the fluid didn't have any particulates, hazing or color change.  I suppose 400 miles might not be enough to show any sign though.

I installed the wheel according to the manual even though it seems excessive.  On Monday I have to change the fork fluid in my friends bike and am planning on using his wheel on my bike to try to eliminate either the wheel or the forks as the issue.

[VirginiaJim]

Good idea.

[gonzosc1]

you mentioned that this happens in the sweepers,  does it happen on both left and right sweepers or just one way???

[Tactical_Mik]

for the sweeper part it happens in left and right fast sweepers.  Until I can figure it out I just make a conscious decision to slow down through those two curves in Kansas. 

[VirginiaJim]

Could it be head bearings or were they adjusted when you did the fork R&R..?

[Tactical_Mik]

I did lube and adjust them since it is easy to do when the forks are off but I plan on rechecking them tomorrow just to make sure.

[Tactical_Mik]

OK I am an IDIOT.  Maybe not quite an idiot but.....

I put my friends front wheel on and there wasn't any difference in the ride.  So I was thinking forks are the key.  After changing out my friends fork fluid this morning I decided to take off my forks, remove the top plug, drain the fluid to check it.  The fluid was pristine as you would expect being two weeksish old.  When I assembled them both previous times I set the top plug to the closet "click" to the specified 13mm without being under.  On one side that was about .26mm over and the other .03mm over if memory serves me correctly.  Today, when I set the gap as it were, I went between click to get within .01 of the 13mm.  I re-assembled and test rode.  My front end bounce has been solved.  I didn't think that such a small of adjustment would matter.  Apparently, on my bike it does.

Thinking this might be my issue I set his forks up the same way.

For the fast sweeper wobble, I will have to eventually travel somewhere to have someone with more experience help me get the suspension setup properly.

[Jeremy Mitchell]

Glad you got it figured out.