Yamaha TRX850 Enthusiasts Forum

(Sorry it was a Wendy's ad, and I've had a few beers! )

My handle bars have started shaking!? I don't know why!

First noticed it a couple of months ago when I got a steering damper. I put the damper on and all of a sudden the bike would just weave, I mean real bad, at 30km/h it was weaving back and forth the entire width of a lane! I couldn't even get to the end of my street.

Took the damper off and all seemed fine. So after putting it on and off a few times in different positions etc. with the same results I gave up and thought I'll look into it later. But today I was just mucking around riding home and I noticed that if I take my hands an inch or so off the bars at about 100k's, the bars just start shaking pretty hard, about a centimetre back and forth! Even at about 50k's there is a noticeable shake.

I'm sure the bar shake is connected to the damper weave, i.e. the damper must amplify instead of dampen the shake. What I'm stuck on is what could be causing the shake??

It had rooted BT020's on it the first time the damper went on, now it has new (1000k old) Diablo's, so the tyres aren't causing it, changing tyres means the wheels have been off and on, so it's unlikely the wheels are misaligned since it feels the same before and after (and yes, I tried the damper with the new tyres, same thing happened!).

Some ideas of where to look for the shake would be greatly appreciated!!

Thanks guys!

A few ideas.....

1. Check wheel bearings
2. Headstock bearings (not loose)
3. movement in swing arm
4. make sure the wheels are straight
5. are the front brakes binding? front disks warped.
6. is the frame cracked/ straight....I had a friend who had this happen.

How old are ya tyres?Are you running 2 different tyres(manufacturers)

Had the same problem put a new set of hoops on and problem solved.Mind you mine wasn't shaking as violently as what yours seems to have been

I had a wobble/shake through the bars at about 60km/h if I took my hands off. Just replaced the stuffed bt020 with a 014 and have been scrubbing it in this weekend and now the problem seems to have gone...

Tyres are fine, both new matching Pirelli Diablo's.

I think the wheels should be straight simply because they were taken off by the shop when changing tyres, and came back exactly the same (though that isn't proof in itself i guess!).

Not completely sure how to check bearings but I'll have a look.

Brakes could be worth a look. I replaced the old 'Braking' brand disc's with full floating ABM discs a while ago. Possibly they are rattling (they are free to move about a couple of mm sideways) and pulling the wheel around.?? Might chuck the old discs back on and see what happens.

Cheers.

Kirk...

I wouldn't bother swapping brake discs back again as the force applied to them by the calipers only affects the wheel and its rotation (fixed relationship between the wheel/axle/disc etc., ). Bearings might have a bearing (geddit?) on the situation, but you'd know if one had collapsed as it would feel more like riding on a flat. My old ST had a badly worn front bearing and all I could feel was an occasional clunk as I came to a halt with brakes - quite a testament to their inherent stability I think! Check by lifting the front wheel clear of the deck (if you haven't got a lift then just tip it back on the prop-stand) get a mate to hold it on full lock then hold the wheel at 9 and 3 o'clock and waggle it (brakes off though) from side to side. Do the same at 6 and 12 oclock - if the bearings are worn you'll feel the play.

Back on course now... Is it an adjustable damper? If so, have you tried winding it right out until there's no damping at all which should replicate the conditions before you fitted it. Then progressively increase the damping until you feel it start to weave, then wind it back until it's acceptable..

I had an old Yam R5 with a wind-up friction damper in the headstock and that did the same as you've described if it was wound up too tight...

G

Check the wheel alignment.

Just because it has been done by a shop don't expect them to get it right -in fact they are more likley to cock it up because they will use the chain adjustment marks (which are not accurate)

just checked mine ,,and with both wheels inline there's 2mm of offset ,,not so bad Ive seen 7mm on cbr600s but on my R1 there is none its dead straight

I hope you get to the bottom of this as I have the very same experience (but without a steering damper fitted).
On my old FZ I could ride 'hands-off' for miles (or as long as it took to slow down from about 40mph to standstill) , even cornering by shifting upper body weight.
The 'rex it has always shook it's head as soon as you let go of the bars at any speed.
I've checked for worn tyres, pressures, alignment, play in any bearing, .. the lot. No joy anywhere so I just ride 'hands-on' all the time.
Is it a TRX trait or does anyone out there have a stock TRX that will track straight and true when left to itself ??

Red Rex wrote: Is it a TRX trait or does anyone out there have a stock TRX that will track straight and true when left to itself ??

I don't know whether you would consider it a TRX trait, as I believe not all bikes experience it, but it is a common enough complaint. We've discussed it a few times. It certainly woke me up the first time I experienced it.

I think that there are a number of contibutory factors and not always one single cause. Headstock bearings, Tyre type, tyre wear, wheel bearings (front or rear), tyre alignment, shock condition (front or rear), suspension settings/geometry are all possible. Oh and it's not beyond comprehension that something like chain wear/slack could even contribute.

Interestingly, I read on another forum about a guy that suddenly started to experience headshake on another bike after fitting a top box, and it's no surprise that weight distribution and aerodynamics can play a part too.

I don't think that mine does this any more, but to be perfectly honest I don't know for sure as I stopped the habit of riding with no hands on the bars.

Mine does it. With mine it seems as the tyres wear the shake becomes more noticeable, but a new set of tyres fixed the problem, until they start to wear and then it came back. Like Burty said, the easiest fix,
keep your hands on the bars

burty wrote: it's no surprise that weight distribution and aerodynamics can play a part too.

Perhaps that's the answer to why it's started doing it .... eaten too much at Christmas, Kirk?

Mine's got a bit f a head-shake too, although mines not noticable at low speed, hands on or off the bars. I first discovered it the last time I went for a bit of a run with a few of the boys when I was playing catch-up after getting stuck behind a car. It was a nice straight stretch of country road and I kept it pinned after passing the car so that I could catch those in front and as I got to around 180-190 it started to shake pretty badly (hands on the bars obviously), scared the living crap out of me I can tell you! I'm still not sure what caused it to be honest, I'd just put new tyres on it and a new set of front wheel bearings, although the chain is starting to get a bit tired and I haven't had a chance to check and adjust the headstock bearings yet. Anyone else had theirs do a similar thing? And if so what was the cause?

I've had mine up to 135 mph and not noticed anything. But the aerodynamics of mine are likely a bit different to standard.

Burty wrote: ... and it's no surprise that weight distribution and aerodynamics can play a part too.

This is exactly when it (sometimes) occurs on mine, when leaning straight up, hands of the bars (adjusting whatever) ánd decellerating at 80k or less

(Yeah I do know It's better to hold on to the bars hehe)

Greetz
Gerben