TOPIC:

Bet you thought that with my smarty-pants rep, this was gonna be yet another riff on Gris and his sordid past, didn'tcha?

Sorry.

This one is actually somewhat technical.

For a number of years, I dealt with a minor, but annoying vibe in my handlebars that was manageable as far as comfort went, but made my mirrors pretty much useless above 50mph or so.

I'd hear of filling handlebars with bird shot enough years ago that my beard was still dark, but between being the type that'd tug on Superman's cape in years past, and rarely owning anything that such a minor adjustment would have had any effect on anyways, I'd never tried it.

But since having devolved to mere humanity, and developing an appreciation for ergonomics once I'd settled into the cop bike, the notion toyed with me more frequently.

This spring, since my neck bearings were in line for replacement anyways, I decided to give it a try.

Doing a little research aforehand, there's an interesting series of comments to be found on the topic at:

www.xs11.com/tips/modifications/mods14.shtml

There's some pretty smart fellers over there that went into detail way beyond my base interest, regarding frequency attenuation and such, and the concepts of partial vs. completely filled bars. Definitely worth a read to those interested in the topic.

Myself, I decided to go the quick and easy route, and just fill the whole bar.

There was a time when WalMart carried birdshot, or so I thought. But PC-ism being what it is these days, and there being some CDs they won't carry because of what people might say, it shouldn't have suprized me to learn that the local one didn't.

But, in the interest of catering to little Ralphies everywhere intent on shooting their own eyes out, they do carry Crossman BBs in handy 3,000 and 6,000 count plastic bottles. Never being one to scrimp on lead - or copper in this case, I went all out and bought the big one.

The only other component necessary for the job was a reasonable cork to plug the bar ends. And since my Better's into cheap hooch, it was a snap to talk her into guzzling a couple of bobbles of Vin de Chardonnay as a favor to my mirrors. As it turned out, her brand had gone high-tech and replaced the fine Sicilian tree bark originals with dense foam cored newfangled gizmos that really worked better in this case than Ma Nature's would have. I took the corks, stuck a set of nails in the ends as centers, then ground the O.D. to match my bar's I.D., plus a pinch for friction's sake.

Plugged one end of the bar with a cork, stuck a funnel in the other end and started pouring. When it filled, I tamped it lightly against my boot and topped the bar, minus the length of the cork. Tapped the other cork in place, and viola.

One proviso: if you have a set of stock KZ bars, the 3,000 count bottle should do the job. I'm now the proud owner of 3,000 extra reasons to teach the cat next door some manners...

The results have been very good, if somewhat short of astounding. My left mirror is good into the 70mph range with greatly reduced vibration. The right still has a bit of a buzz in it, but is significantly improved. I've managed to tune out a bit more of the buzz by adjusting the switchblock/master cylinder position on the bar.

So, if you've ever been curious about trying it, filling handlebars with shot is a cheap and reasonably effective tactic against handlebar vibration.

Knowing the author of this tech post as I do I would be willing to bet he has instituted and electronic uncorking device that will send bookoo BB's cascading over the blacktop and thus sending the coyote chasing him careening into the side of the mountain. I personally would have took the Peter Fonda solution and stuffed my handlebars with thousand dollar bills which would also provide many hours of extracurricular activities at the next tittie bar.

My personal preference can also be traced directly to the reason I have 3 ex's and a bank account in negative numbers.

They used to sell something called a Bar Snake or something like that. I have a review of it in a old mag somewhere in this cave. I may have to brave an exodus to WalNutto Mart. cool..........

i think i know who's bike imma steal;)

Yup, this is common for the thumper crowd.

You'll find a lot of KLR650's with stuff in the bars. But as mentioned, resonance frequency is a big deal. It's hard to find a harmonic, sometimes.

Short version: Yes, it works. And, it works well.

mykznme wrote:

i think i know who's bike imma steal;)

I wanna buy a ticket to watch these proceedings from uppa tree somewhere not *too* terribly close by - Gypsy looks like she could use a good meal...



Post edited by: Pterosaur, at: 2006/05/31 23:24

Cool, been wondering about this for some time now. I can just use my bar end weights for the plugs. So, bars with BB'S 50% vibe reduction? 80%?

FEF wrote:

Yup, this is common for the thumper crowd.

You'll find a lot of KLR650's with stuff in the bars. But as mentioned, resonance frequency is a big deal. It's hard to find a harmonic, sometimes.

Short version: Yes, it works. And, it works well.

How are your bars set up?

gas wrote:

Cool, been wondering about this for some time now. I can just use my bar end weights for the plugs. So, bars with BB'S 50% vibe reduction? 80%?

Actually, the vibe reduction can be improved by only partially filling a given set of bars. It's not how much weight you add necessarily, it's *where*. Every material item, including yourself, has a "harmonic frequency" - or more accurately frequncies. That's why your teeth buzz when you stick your ear against a cam cover wanked up to 9 grand or so, and your guts may rumble when a train goes by.

Handlebars vibrate because they are oscillating sympathetically at a frequency that matches with some multiple of the vibes given off by your motor. That's transmitted through the frame to the triple trees, to the bar clamps to the bars.

The trick is to find that frequency and squelch - or "damp" it.

If you wanted to get all Spock about it, an occillating transducer could be wired up to an ocillscope to pinpoint the harmonic and then add incremental amounts of weight until the exact amount of damping was applied.

Or, you can do it my way and just fill the damned thing.

Or, you can get 4 corks, jam the first pair up to the first bend in the bar inboard of the grips, fill only the outer 8" to 10" or so, and see what that does.

It _can_ be an exact science - they spend gobs of money tuning vibes out of airplanes, but it didn't become a real issue until BMW, Ducati and the Japanese got into counterbalancers in the early-mid 70s...

Just to make things more complicated, the material of the bars malkes a big difference. Switching to aluminum bars can help too.

Post edited by: absolutepat, at: 2006/06/01 03:41

Franco: And now my friend, the first-a rule of Italian driving.
[Franco rips off his rear-view mirror and throws it out of the car]
Franco: What's-a behind me is not important.

tganek wrote:

Franco: And now my friend, the first-a rule of Italian driving.
[Franco rips off his rear-view mirror and throws it out of the car]
Franco: What's-a behind me is not important.

hehe... I *waaaay* know better than to axe if I won anything...

I dug the Dago driving lesson, but my *favorite* part was Adrienne's Barsooms...

Post edited by: Pterosaur, at: 2006/06/01 06:25

Now, I tried the BBs in the bar last year. I had aluminum motocross bars and I plugged one end with a plug of shoe goo and filled it up. I plugged the other end with SG too. Unfortuantely, it was either a loss of a few BBs or something inherent to the BBs in the system (and there density versus lead) whenever my bike got to a certain rpm range, the BBs themselves vibrated and made a slight rattle sound too. This year, when I went ot superbike bars I replaced the BBs in the setup with a combination of 20-guage slugs and birdshot BBs. No more vibration from the BBs. However, since I never had these bars on before and I went to Napolean barend mirrors, I have no real place to compare it to. I had thought about getting some poly-prop rope and working it into the center of the bars to fill the void and keep the weight out more toward the ends, but didn't do it in the end--maybe mext time.