Why does my bike suddenly wobble?

[ducpainter]

5 mm drop is *very* aggressive.

I took mine down 2 mm, and anymore was totally unstable. Without raising the rear. 

I guess it depends on what you like or what you are used to.

My hoop style Monster is raised as far as possible with the heim joints.

I weigh about 175-180 in street clothes and run a 10.0 rear spring

There is 25 mm of fork tubes sticking above the top triple.and I have .85 springs and racetech valves with a modified stack

The thing turns like a 250 and is stable in turns and in a straight line at speed.

Can I say that someone else would like it...I know some do.

YMMV.

I'm with Statler on the rider input theory...

as soon as the OP checks his steering head bearings.

[stopintime]

Sounds like you have the bases covered from all the good input.

I have no FHE with your swingarm type, but is it possible that with the gear/chain swap you ended up with less swingarm length (shorter wheelbase) and/or more rear ride height than you expected?

I think you indicated 36mm rear rider sag.  What is your front free/rider sag?  Your static geometry might not be so different than most monsters out there, but with such a heavy rear spring you might not be loading it up much in a gentle sweeper, so the attitude of the bike through the turn could remain too aggressive.  Just speculating out loud here.

BK

Good points - there is some height differences through a chain life - it changes a little for each adjustment. I don't know where it is at the moment though.
The rear of my bike would certainly sink in much more through a turn than it's doing now.

5 mm drop is *very* aggressive.

I took mine down 2 mm, and anymore was totally unstable. Without raising the rear. 

Some people say "won't notice" - others say "very aggressive" about a 5mm drop. The only thing I know is that other than the high speed wobble, my bike felt very stable and not at all twitchy.

Thanks for all the input guys - keep it coming. I didn't spend all that cash without expecting everything to work well. I WILL make it work as planned

[stopintime]

..........................................

I'm with Statler on the rider input theory...

as soon as the OP checks his steering head bearings.

Yeah - blame the noob       Actually, at least in theory, it's more likely that I did something wrong than the shop guys - they probably know their stuff - I don't.

How can I check steering head bearings? I got a new DP steering head bling nut. Wouldn't you expect the shop to to check the bearings while changing the nut?

[ducpainter]

Yeah - blame the noob       Actually, at least in theory, it's more likely that I did something wrong than the shop guys - they probably know their stuff - I don't.

How can I check steering head bearings? I got a new DP steering head bling nut. Wouldn't you expect the shop to to check the bearings while changing the nut?

I'd expect that they checked it as part of a suspension rebuild/set-up.

The guy that does my work checks them every time he gets his hands on the bike.

It's common for the wear or detenting (the technical term is brinelling from shock loads while not rotating) to occur right at the center.

I had a vicious wobble develop on my bike. The bearings had a wear spot very near center. You'd enter a high speed turn and the steering would need a little more so you adjust and because it took more effort to get past the detent I'd over correct...then correct again...and again...and again...each time in the opposite direction. At 100 mph that translates into some serious pucker factor.

It wouldn't hurt to ask them if they checked. It's not hard to do your self.

[BK_856er]

How can I check steering head bearings? I got a new DP steering head bling nut. Wouldn't you expect the shop to to check the bearings while changing the nut?

Suspend the front (I used an A-frame ladder and tie-downs to the bike frame) and shake the forks front/back.  Clunking or clicking indicates excessive head bearing slop.  Also check for smoothness of operation.  With the bike on the ground it would be a good idea to loosen and then torque the special nut to spec to remove all doubt, but that requires a special tool and suitable torque wrench.  The first check is easy and will alert you to any gross issues.

BK

[stopintime]

I need to fire up the geometry squad here.....

(Think I know how)

The front is probably lowered as much as 10mm
The stock triple is "curved" - it falls down from the steering head area towards the fork pinch part - by about 10mm. The SpeedyMoto triple is flat.
Comparing the two will show a difference of about 10mm.

But I still think my bike felt stable to ride 

[Moronic]

Bit of a long shot, but I'm wondering whether your rebound damping might not be coping with the much stiffer rear spring. I imagine your guru must have revalved the shock, but valving or adjustment might not be quite right first-up.

It is possible (if again a long shot) that the problem appears only in left turns because only those few high-speed lefts where you've tried it have the sort of bumps that upset the suspension.

A little bit of oscillation at the rear can easily feed into the front through rider and handlebars.

[Roscoe]

It is possible (if again a long shot) that the problem appears only in left turns because only those few high-speed lefts where you've tried it have the sort of bumps that upset the suspension.

This is what I was wondering. Maybe find some right handers that might induce the wobble. Remove one piece to the puzzle at a time.

[stopintime]

I went for short and not so fast ride today - very conscious about what was going on.....

First, the bike is very stable on the highway, but it's obvious that it steers much quicker now - much more sensitive. I was cruising through a village, kind of upright with almost straight arms - hit a small pothole that surely wouldn't have upset the bike before, but today it did. I went back, leaned forward and relaxed my grip - ran into the same pothole and had no reaction (other than the compression).

I found that I do the thing with the left arm straighter than the right (Statler's advice). I really have to work to get into the forward position / clip on / loose grip thing - I thought I was being ok with that, but there's some work that needs to be done before it gets all natural.

I'm very close to accepting the changed geometry + faulty rider input as the main reasons for the wobble, but I will check everything to have the best understanding and to make sure everything is working to my advantage.

Talk to you soon

[Speeddog]

Good that you're getting it sorted. 

[silentbob]

So the problem was the nut that holds the handle bars then.   

[stopintime]

So the problem was the nut that holds the handle bars then.   

"it's hard to be humble when you're as great as I am" 

[DucHead]

"it's hard to be humble when you're as great as I am" 

I think there's song with the lyric, "Lord it's hard to humble when you're perfect in every way!"

Glad to hear that you're adjusting to your new riding position.   [moto]   It'll take a bit, especially since I think you've mentioned that you're well over 6 feet tall.

[stopintime]

Guys, just a little update after the first 600 miles.....

I had the suspension shop go through the list of suggestions today - including the "too stiff rear spring" issue.

The changes are quite radical and they are new to me, but I'm starting to understand what is happening and what I need to do.
I need to be very aware and to work hard on my technique. Before the changes I could get away with a lot of lazy attitude - now I get a clear message from my bike every time I forget to watch my rider input, forget to look through turns, forget to position my body properly a.s.o.

If I follow Lee Parks' book and everything I learned from DML/DMF it works great. If I don't, the bike tells me to sharpen my actions.
I wanted to take my skills to the next level and that's what's happening now.

The first track day is only a couple of weeks from now - I guess I'll know a lot more then.

If I decide to back up a bit - my options are: lowering the rear, adjusting the rear suspension (preload/rebound), add a steering damper, play more with tire pressure - anything missing?


Thanks again for helping me understand what this riding thing is all about - your help is valuable and inspiring

[LA]

Even if you have the suspension well sorted, a Monster, especially one driven an enthusiastic person, with the ride height adjusted the way yours is, needs a good steering damper.  I put an Ohlins on mine and it made a noticeable difference, especially when cranked over on bumpy pavement.

Over the years I found that very light on the controls is paramount too.

Mines down about 8mm in the front and up 25mm in the rear too.

LA