New to me Buell xb12s! Forks vibrating on braking.

[jivenene]

I've been wanting a xb for the last 15 years, I finally scored a nice condition 2006 xb12s with 18k mi on it. It is a 1 owner bike, came with service manual and parts catalog. I found only a few things wrong on my post purchase inspection, such as a frayed and almost broken clutch cable...

On my only second ride today, I noticed some chatter from the front end under braking. I thought it was coming from the headlight assembly vibrating, but after looking more closely, i saw that the forks were vibrating. After the ride, I inspected more closely and found that the bottom triple clamps don't even clamp onto the fork tubes! Looking down, I can see a gap all the way around the fork tube at the lower triple. I measured everything out and it seems this bike has the 41mm forks on it, not the 43. The inner tubes are 41mm, the outer tube is 54mm diameter at the triple clamp points for lower and upper. I can only assume that the PO had replaced the stock 43mm forks with 41mm forks, using the correct top clamp, but didn't change out the lower clamp for the smaller 41mm forks.

Am I assuming correctly, or is there something else I am not understanding? are there part numbers stamped into them so i can verify?

thanks!!!

 

[Barrett]

there is a wide variety of triple clamp combinations as well as fork tube specs for the entire run of XB series buells.
to keep it simple, so that identification of your parts as well as what the current problem might possibly be, use these specs:

1-Showa never stamped Buell specific part numbers on any suspension components that i'm aware of. the fork tubes, when new, did have a small identifier sticker on each and a stamping, so that assembly line guys knew what went where.
2-2006 XB LIGHTNING S series 12 tube and triple clamp identifiers:
30-1/2 " overall length
slider(outer fork tube) upper section OD-54mm
slider (outer fork tube) lower section OD-56mm
upper and lower triple clamp ID should correspond to the above specs. if not then something radically askew and incorrect.
determine what that is by taking simple measurements and reporting back with results. i'll look up your specs and find out what you have.
NOTE: leave it parked in garage till you identify the problem and resolve it. unsafe in its current condition.

 

[34nineteen]

The master has spoken.

 

[jivenene]

Thanks Barret!
Yeah like I tried to say in the 1st post, the forks have a 54mm OD on top and bottom mount point, but triples are 54mm up top, 56mm on bottom, hence the small gap I can see, and the shuddering I can also see under breaking.

I've slept on it, and it must be that the PO had 41mm forks put in, but they never changed out the bottom triple. Weird.... or should I say careless.

Anyway, my solution will be to fashion some 1mm shims and clamp on those, I don't see the harm in that. I don't have the time to install the correct lowers, doesn't seem critical for a street bike.

 

[Barrett]

yes sir my pleasure. i'm sure "shimming" the difference that you've been mentioning between the fork slider, and the lower triple clamp location holes has been done before. BUT keep in mind that the fit between the sliders and the 4 total location holes in the triple clamps is a very close tolerance fit. the pinch bolts apply the clamping force and the sliders, where clamped, have subtle grooves, if you will, that help generate a bit of friction or "catch" when clamped. you'll lose that aspect with any sort of shims. the total clamping force applied at all 4 locations is what keeps both fork tubes solid and movement-free in both the vertical and longitudinal directions. extremely important.

your 2006 S model from new had 43mm tubes.
all 2003-04 XB models had 41mm tubes except the "low" models being the SL and SCG which continued with 41mm tubes.
2005 and up are 43mm tubes. exceptions are in the X series models.
use this info if searching

 

[Cooter]

It takes all the braking force of the bike, not to mention the other important thing that your life depends on. Steering. And you'll be on the street with other humans that don't want you to kill them (or yourself either).

Install the right triple, or the right fork tubes. Period.

If it takes you an hour, you're slacking. Then sell the take-offs to re-coup your expense. It's not even worth thinking of the horrible butchery you are suggesting.

Have a nice day:eagerness:

 

[jivenene]

I ended up getting some 1mm aluminum sheet cut to size, but the installation in my head was much easier than practice lol. Even with spacing out the clamp points for more gap, the forks were always close to 1 side of the hole they were in. I had the bike hanging by the bars in different positions, but the shims still required some tapping in. I took great care in avoiding hitting the fork tubes, and consequently it took forever! I also had to file down and dremel the shims so they would not be sharp and bite down into the clamps or forks. Finally got them all clamped and torqued down, pretty confident they will not slip or twist in any way. Will update if further problems arise.

Anyway, one of the adventures of getting a used bike that was apparently worked on by the Shakespeare monkeys...

 

[34nineteen]

Congrats on getting those fitted, but wouldn’t it have been better to just fit the correct clamp?
If something goes sideways, you could too. It will probably be ok, but that’s not a chance I would take.

 

[outthere]

Shakespeare monkey. I need to look that up