front end wobble, suspension issue?

[VisceralReaction]

OK so I know we've talked about this before and I just need some input personally.
I put a new spring on my rear end of my ST3 last year. The bike developed a wobble in the front end at about 50mph
when I come off the throttle and the bike decels. At about 50mph the wobble gets pretty pronounced.
During acceleration its very minimal.
I am wondering if I need to either add preload to my forks OR put heavier springs in the forks.
Thoughts?
Thanks!

[Speeddog]

What spring did you put on, and how much do you weigh?

[VisceralReaction]

I put a 750lb on it and I weigh 200. I was trying to hit a middle ground of slightly stiff
with me alone and comfy with my wife (180lbs)

[Buckethead]

Reviving this because it's relevant to me.

New set of tires on my bike (ContiMotions). Rear was on for a couple of days while waiting for the front to come in. Scrubbed it in, no problem, nothing weird.

Front tire goes on without a hitch. Take it out for a shakedown cruise and everything's okay for a while. Then I start to notice that while cruising at 35-40, steady throttle, there's a low frequency (2-3hz, I'd guess) front end wobble. Barely perceptible through the clipons, but I can see my headlight and turn signals wobbling. Not serious, bike seems to track just fine, stable through the corners, etc, but I noticed it and it bothers me.

I'm probably gonna get a steering damper at some point in the future, but I'd rather have this sorted out first. Don't want to use a damper to cover a problem.







Also, I'm deathly afraid of tank slappers. No judgies.

[zooom]

worth checking your steering head bearing !!!...just a thought FWIW

[Buckethead]

I've thought about that. 7 years and 15k miles, so they're probably due.

What makes me think that they're probably NOT the culprit is that it suddenly showed up after I had a new tire mounted. I suppose it could just be out of balance. 

[Speeddog]

Tire sizes, rim sizes, and which model bike?

[Buckethead]

2006 Sport 1000 with 999 10-spokes. Continental Conti-Motion 120/70/17's.

I think I may have figgered it out. Went out to go look at the tire size (didn't remember if it was 60 or 70) and lo and behold, there's a giant sticky patch where there used to be some wheel weights. Shop I took it to to mount/balance wouldn't have left stickies from the old weights. My guess is the new ones came off. 

[battlecry]

I use gaffer tape over my weights.  It is similar to ductape, with more fabric. 

Don't discount the tire being part of the problem.  Unlikely, I know, but I think an unbalanced assembly would get worse with higher speeds.   Large frame modern Vespas have a stability issue, and are sensitive to tire type when decelerating around 30mph or so.   Go figure. 

[Howie]

If wheel balance does not take care of the wobble check wheel run out, particularly axial.  I forgot, are you running spoke wheels?

[Buckethead]

I forgot, are you running spoke wheels?

Not anymore! 



999 Marchesini 10-spokes.

Took it out for a "little" ride today. http://www.ducatimonsterforum.org/index.php?topic=56912.0

Only ever showed itself at constant throttle between 35 and 40. No other issues.

Planning on getting the wheel re-balanced this weekend.

[koko64]

Very interested in hearing what you think of the Conti Motions.

[d3vi@nt]

Planning on getting the wheel re-balanced this weekend.

Please post your results -I'm having a similar issue and wondering what to do about it.  You're in FC, no? Where do you take your bike for service if I may ask?

[Speeddog]

Sounds like an alignment issue, sure you got the spacers in right?

[Buckethead]

Very interested in hearing what you think of the Conti Motions.

I like em so far. I'd heard they take a while to warm up, and I'm not a terribly aggressive rider anyway, but they've responded admirably to everything I've thrown at em. Nary a twitch or a skitter.

You're in FC, no? Where do you take your bike for service if I may ask?

Yup. Pulled the wheels myself and took them down to MotoAdventure Kawasaki. I like the guys there and they cut me a deal when they can. Headed down there tomorrow and I'll let you know how it works out once I've got it all back together.

Sounds like an alignment issue, sure you got the spacers in right?

Pretty sure, but it's worth double checking. I typically put the spacers back on the axle in the same orientation they came off while I've got the wheel off just to keep from losing them, but it's possible something got switched around while I was working.