Return of the Beta head clunk

[dan williams]

So after a complete disassembly of my forks to chase another noise I figured I'd throw a caliper on the top triple clamp as the head has started clunking again and I'm getting tired of repacking the space with Teflon tape every couple of months. The difference between the spindle and the hole in the clamp is a good 0.006 of an inch. I've ordered a sheet of 0.003" brass shim stock. We'll see if that works but I was wondering if anybody else has measured the clearance between these two parts as it seems to be a fairly common issue. I'm wondering if it would be worth having shims machined? Not worth it for one bike but might be worth it if there is demand. Still tempted to just buy a new top clamp since they now have a pinch bolt.

[mcman56]

Some questions - Shouldn't it be the clamping force rather than the clearance that keeps things from moving....like the rear axle in the swing arm?  If movement is based on fit, wouldn't you need a press fit to prevent movement, like a big end pin in a crankshaft?  I assumed the pinch bolt was to keep the bolt from loosening thus preventing loss of clamping force.  

[dan williams]

No clamping force. The fit between the spindle and the top triple clamp shouldn't be an interference fit but close. It should be tight enough that a few mild taps are required to slide the top clamp on. On this and my past few Betas it's been absolutely floppy once the top nut is removed. The top nut is meant to hold the clamp on not fix it in place relative to the spindle. The leverage of the forks is sufficient to force the clamp to slide on the spindle and clunk no matter how tight the nut.

Looking at the spindle it seems Paioli ran the thread for the bearing cap too high and just plain got the clearance wrong to speed up assembly. Another thing that is a bit odd is there is a  relief about 3mm wide around the bottom of the clamp almost as if there was supposed to be an insert there possibly to allow for manufacturing tolerances.

[mcman56]

I have a 2014 Factory model and it does not have the nut under the top triple clamp for setting tension on the steering bearings.  The "fork adjusting ring nut" shown on the 2013 evo parts list is not there.  The "ring nut" is shown on the standard 2014 model parts list.  I discovered this when I removed the top clamp and the forks started to fall off.  So, on the factory, the top nut sets the tension for the steering bearings and holds the top clamp in place.  I don't remember how well the top clamp fit but it does have the pinch bolt.  Not teh same bike but I was getting a head clunk on a 99 Kawasaki Concours when hitting the brake on the freeway.  On that bike, fully torquing the nut above the top clamp removed the clunk.  

If these come in the right size, they may work as a thin sleeve.

http://www.parker.com/portal/site/PARKER/menuitem.7100150cebe5bbc2d6806710237ad1ca?vgnextcatid=2633738&vgnextcat=SHAFT REPAIR SLEEVES&vgnextoid=f5c9b5bbec622110VgnVCM10000032a71dacRCRD&vgnextfmt=EN

Or, if you know have access to machine tools, you could bore or ream the hole in the top clamp much larger and press fit in a reducing collar that would be a tight fit on the steering spindle.       

Edited August 30, 2017 by mcman56
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[dan williams]

Hmmm sounds like a way to save a few ounces on the factory bike. Not sure I like the implications for long term reliability. I've seen designs where the bearing cap has an extension and the top clamp slides onto the cap. More than one way to skin a cat(fish). My brass shim stock has arrived so I'll give that a go first.

Nice find on the Parker "shaft saver"

[trapezeartist]

On 8/30/2017 at 3:39 PM, mcman56 said:

I have a 2014 Factory model and it does not have the nut under the top triple clamp for setting tension on the steering bearings.  The "fork adjusting ring nut" shown on the 2013 evo parts list is not there.  The "ring nut" is shown on the standard 2014 model parts list.  I discovered this when I removed the top clamp and the forks started to fall off.  So, on the factory, the top nut sets the tension for the steering bearings and holds the top clamp in place.  I don't remember how well the top clamp fit but it does have the pinch bolt.  Not teh same bike but I was getting a head clunk on a 99 Kawasaki Concours when hitting the brake on the freeway.  On that bike, fully torquing the nut above the top clamp removed the clunk.  

If these come in the right size, they may work as a thin sleeve.

http://www.parker.com/portal/site/PARKER/menuitem.7100150cebe5bbc2d6806710237ad1ca?vgnextcatid=2633738&vgnextcat=SHAFT REPAIR SLEEVES&vgnextoid=f5c9b5bbec622110VgnVCM10000032a71dacRCRD&vgnextfmt=EN

Or, if you know have access to machine tools, you could bore or ream the hole in the top clamp much larger and press fit in a reducing collar that would be a tight fit on the steering spindle.       

I've used the SKF equivalent to repair a worn shaft in a water pump. It lasted twice as long as the original before finally needing total refurbishment. Not sure how it would work in this application though.

[dan williams]

0.003" shim seems to have sorted it but I haven't really put any hard riding (if what I do can be called hard) on it yet. I'll have a much better idea after tomorrows event. 

Anybody want some brass shim? I have a whole roll of it that I only used about a square inch of.