Beta Head Clunk

[dan williams]

First event on the new bike answered my question of, "Will this bike have the same head clunk as every other Beta I've owned?" The short answer is yes. Every inattentive hit to the front end was met with a clunk through the bars. I've seen two reasons for this on Betas; First because the bearing races don't fully set into the aluminum steering head and require a retightening every few rides for the first month or so to settle in. Second because the top triple clamp stem hole is not the correct size being slightly too big so once the tension of the initial assembly loosens up the top clamp moves back and forth on the stem. Neither is acceptable as far as I'm concerned so the front end is coming apart for a little inspection this week. I'll try to document the procedures for your entertainment. Now if I can just get my hands on some thin kynar tape.

Also thinking of going back up one size to the stock pilot jet as it was slightly laggy off idle.

Other than that I gotta say it is an amazingly stable chassis.

Edited April 30, 2013 by dan williams

[sir dabs alot]

I had the same problem on my '08 and tried to explain this to no avail. I couldn't detect play by grabbing the fork legs and even wondered if it was a loose front disc pads or caliper. Anyway, good to know I wasn't imagining things. It was very distracting annoying clunk!

[dan williams]

Yeah my '08 had the top triple clamp hole too big. Some thin Teflon tape took care of it but I'd prefer something that didn't cold flow like Teflon. That's why I'd like to try the Kynar tape on the '13.

[billyt]

Dan All of the above you said not withstanding.

One other thing I found was that the Fat Bar clamps inside diameter does not fit the outside diameter of the fat bars.

Basically the bar clamps are only clamping on a small circumference of the bars causing it to jerk or wiggle when dropping off something other than a blade of grass.?

It is easy to check by either using your wife's lipstick (or yours) coating the inside of the bar clamps tighten down and then loosen and remove looking for the lipstick witness marks on the bars to how much it is actually contacting the bar circumference. With a Beta 4T I owned it was not much holding the bars on and it would clunk quite a bit until I matched the bar clamps circumference to the bar circumference. A long shot I know but it was reality on that particular bike.

On a side note: On any bike that has bar clamps with a small dot on them (i.e. Montesa) it is imperative that one matches up the dots on bar clamps and triple tree stanchions and then tightens down the side with the dots first. Once that is done tighten the non dot side to preference.

WHY? Because the bar clamps with dots on them are not even and if you turn it upside down you will notice that one leg is taller than the other. They want one side tightened down mating to the surface of the triple clamps and the other side arcing down across the bars.

Non dotted bar clamps are meant to bridge across bending evenly over the bars as one tightens them down side by side.

Edited April 30, 2013 by billyt

[dan williams]

"It is easy to check by either using your wife's lipstick (or yours)"

Thanks Billy for starting my day with a laugh and the always sage advice.

[mcman56]

Shouldn't the top nut keep the top clamp in position? I just had this problem on a Kawasaki Concours. It sounded like the front end was going to fall off but I could not find any looseness when pushing the front end back and forth. Eventually, I found that the top nut was loose and once torqued the noise went away. The top fork clamp is a very loose fit on the spindle.

My Beta did have some weird ticking type front end noise when the front wheel would hit the ground. I cleaned the fork tubes really well and torqued all of the fasteners and the sound went away. I suspect the tubes were moving a bit in the clamps.

[chewy]

Just another of those irritating little things we come to expect from trials bikes? For me the most off putting thing regards beta is the dreadful idea of designed to break expensive plastics. Generally a good bike though and of course here in theU K a very good level of service from the importer.

[0007]

Can you explain exactly when the clunk happens?, top out, bottom out?

One thing that a lot of forks do is move around especially at full extension when the bushings are their closest together

You can feel it when the spring is out and look for fore and aft play in the leg

[dan williams]

With the loose top clamp you can place a finger behind the stem nut on the top triple clamp and feel movement while rocking the bike back and forth with the front brake on. That nut can't hold tight enough to prevent the torque from moving the misfit pieces. The clearance must be dealt with.

With the bearings not seated you can feel movement placing a finger between the top race and steering head of the frame.

[dan williams]

I see the 2014 has a pinch bolt now.