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Discussion Starter · #1 · (Edited)
HI guys,

this is my first time on the forum and hoping you may be able to help. I have a 2002 TA 650 and decided to turn it into something quite special and so far so good. We all know the TA could do with a few more Bhp but still manage to love the bike for all it has to offer, my only deal breaker is that despite all mods to date I still get an annoying and not very reassuring wobble when in a straight line at highway speeds (i.e. 80 mph and above and definitely when traveling at 90 mph and above). I know the TA is not a road racer but too often before reaching our destination we have to cover some boring highway and my feeling is that the quicker I get over with it the better (within reason that is).The bike is great and I have managed to better it, including the wobble which is similar to what you would experience some times when crossing lanes at speed. The bike is now well planted but for some obscure reason the wobble is still there when driving fast in a straight line. Just to give you and idea my transalp has had:

1) New baring front and back
2) New Metzeler Tourance tires (130 at the back)
3) Tapered roller head barings
4) Wilbers Progressive front fork springs
5) Denser 15 SEA for oil as the Wilbers recommended SEA 5 oil is way to weak
6) Amazing custom Nitron rear mono shock with HPA, Rebound and Compression as well as ride hight adjustment
7) Nitron custom mono has raised the rear by 15 mm
8) Honda original lower seat
9) Touring Givi tall screen (my hight is 173 cm and creates lots of buffeting and noise on my helmet)
10) Original Honda side pannier racks and top box (I generally always have the top box, but the wobble is still there even without the box)
11) Hell crash bars
........and the list goes on.

Next on the menu is a set of Arrow Collector and Hell braided hoses. I did all the work with the idea to do a lot of touring but if I don't manage to get rid of the wobble I'll always be thinking of upgrading, but nothing more I can do, so changing the bike to something like a BMW 800gs but would rather live with the TA. I have tried my friend's factory standard TA 600 and although it feels heavy as hell especially in the front, vibrates more, and the standard front suspensions are scary soft when breaking, the bike feels planted like a train on tracks, even too much ffor my liking, but at least there is no wobble on a straight line at speed.

I have also had the wheels balanced, the spokes quickly checked but no re-set.

COULD ANYONE OUT THERE HAVE A CLUE AS TO WHY THIS WOBBLE IS STILL with me??? Once again, the bike is great but on a straight line at 85 mph and above I still get this sensation, less than before all the mods but it should have gone by now. When traveling at 95 to 100 mph the wobble is quite obvious and doesn't feel very safe.

Hope you can help.
Cheers

PS - if you are wondering if the progressive springs are worth the money and hassle, I would suggest first trying the standard springs with 15 to 20 SEA fork oil and see how it goes. While if you are wondering about the rear Nitron monoshock, well the answer is YES it changes the bike and will put a smile on your face.
 

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i've heard that backbox wind turbulence, usually at high speed can be a factor.
 

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Drop the fork oil to the recommended and in crease the tyre pressure by one PSI. The harder front could be causing the vibrations.


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Topbox?

I personally have been at a 100mph with side panniers and no topbox and while the wind protection was not sufficient, the bike remained stable...

On another occasion with a very overloaded bike and a top box, i did feel a wobble at 104....but i put it down to a very light front...
 

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When I had my Trannie, Tourances loved standard PSI; 36 and 40 if I recall.

I pushed my oil up to 7.5 weight and with a spacer, I definitely wouldn't want thicker oil.

Wobble at speed..... I'd double check your head bearings for being too loose, or of course too tight.

Actually, I'd also check your jacket......

Hey??!!!

No, I am being very serious. Last weekend I went up to Manchester. 300 miles each way mostly motorway. With my gortex jacket and at a constant 80, sorry 70mph... on my R65, smooth as silk.
Stopped at services to put on my fluo Dickie and I got awful and sometimes very scary wallowing and smimmying at speed.
 

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Iv'e never experienced a bad wobble on my 04 650, but shortly after I got it I noticed I could feel a bar shake (tank slapper type) the bike was bog standard and so all I did was make sure the oil level was correct in each leg which it was, and that wheels and tyres were OK. The slap was bad enough that I could never take my hands from the bars, anyway shortly after and not being happy with the standard fork diving under braking/hitting sharp bumps I decided to fit some fork valves and apart from everything else I could say about the valves the one thing I will say is the bar slap was totally gone and I could ride hands off just about anywhere.
So even though you have changed the springs and the oil weight you could still have imbalanced damping, because that is the only thing I could put my problem down to.

Windmill John has a very good point also about clothing/aerodynamics and looking back perhaps the one time I did have a fair wobble was riding over the mountain in the isle of man doing about 90 plus, with the sit up position and a fair wind ripping at my shoulders it did happen bad enough to shut off or be off!
 

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Welcome to the forum

Have you raised the front end to match the raised rear in order to re-balance the geometry

I ran a VTR SP1 on track and initially we needed quicker turn in and more ground clearance to match the R1s and GSXRs of that era. We revalved and dropped the forks through and raised the rear by putting a spacer on the shock mount making the length 8mm longer which translated to almost 30mm rear increase in ride height. This gave the turn in and ground clearance we needed. It gave Ducati clearance and all that touched down with rearsets on was the belly pan

The downside was high speed instability. Turn in was great and the ability to change direction mid corner and still have grip at the front was great. At speeds above 155 mph the bike would fishtail due to the change in geometry. This did not worry me as there were few tracks that we would get that fast and need to sustain it.

The other area you might have a problem is in a mis-match between the front and rear shock - if it's too soft at the rear (depending on how you have specified the shock) compared to the 15wt oil you have in the front this will have a similar effect as the could be causing the wobble

I have a Nitron on shock and currently run the front as standard with 7.5wt +10ml reduced airgap

http://www.xrv.org.uk/forums/product-reviews/83386-nitron-ntr-xtreme-shock-rd07-07a.html
 
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Change one thing at a time. Eliminate the free stuff first, sounds like you have checked your boxes (mine causes a wobble when in deceleration from 40mph to 30 mph.
If it is nothing silly then find someone who is really good at suspension and pay for their help. Yours is way off standard so could well be messing up your dynamics. Mine was set up by someone here in nz so recommending them isn't much point. I'm still running the stock rear shock which has been rebuilt 3 times now and is probably due for replace soon. The front I had emulators and high quality oil installed 130,000kms ago and never needed to touch them.
 

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Does the 650 TA have different tyre pressure from the 700, 29 front and rear solo, 40 rear with pillion?

Paul S is on the money for me, you completely altered the geometry of the bike without thought for the stability, go and have the thing set up by a suspension specialist.

The top box will create a vortex around the back of you creating back pressure at high speed. That will create downforce on the front of the bike. If the rake from rear to front is too harsh that could be your instability.

Does the rear or front feel light?
 
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When I had my alp 650 it would start to weave at 70+ if the panniers were on. With just the top box it was fine

Paul

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Another one for geometry.
You have raised the rear & added progressive springs at the front (more sag???)

Check the suspendion sag f+r, if that doesn't work, is there any way you can lower the rear to standard or raise the front to match the rear?

Mine occasionally has a bar shimmy at walking pace but is solid & stable (as much as an Alp can be lol) into 3 figures (on the Autobahn)

Phil
 
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