violent head shake MKIII

I recently rI need some opinions from you guys on what could be causing my head shake. I recently replaced my euro bars with clubmans, rebuilt the forks, and replaced my drive chain--all at the same time. Ever since refitting the parts, I the bike has a nasty head shake that makes me not want to ride it. Everything was torqued per specification via the factory service manual. Prior to the work however, the bike was smooth as silk at any speed. I'm kinda at a loss as to what could be causing this.

What sort of head shake? Low speed, high speed, on acceleration, on bends?

Any speed above 15 mph. It is uncomfortable with hands on the bar (but Manageable), if I remove my hands it turns into almost a tank slapping situation.

of the three things you said you recently did only rebuilding the forks seems relevant to head shake

there is a frong end bouncing and fastener tightening sequence to follow after your rebuild

it is quite possible that the forks are not aligned equally, something is off in the rebuild steps?

can you outline just what you did rebuild and if you followed the shop manual sequence?

drive chain?
is the rear wheel aligned correctly?

woops mark posted while typing mine up -
did replacing the chain mean removing the rear tire, or loosing it up? rear wheel alignment (or tire wear) can contribute to the symptoms you describe too

nortncom said:

I recently rI need some opinions from you guys on what could be causing my head shake. I recently replaced my euro bars with clubmans, rebuilt the forks, and replaced my drive chain--all at the same time. Ever since refitting the parts, I the bike has a nasty head shake that makes me not want to ride it. Everything was torqued per specification via the factory service manual. Prior to the work however, the bike was smooth as silk at any speed. I'm kinda at a loss as to what could be causing this.

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Most Commandos have a slight shake at around 30MPH but yours sounds much worse.

As others have mentioned, wheels alignment and fork alignment are the first things to check since you have worked on them. I would also check the usual suspects: Tyre pressures and tyre wear, steering head bearings, swinging arm bushes.

Try those and see how it goes.

I hold with p-john, air might of leaked down while shut down and by far tires make or break Cdo handling. For most 32 rear 30 front is good start and enough low air in front not to conflict so much with rear. I'd fil tires to upper 50's then bleed back to maybe help take any tire set up molding back more round. Also remember the Dunlope weave/wobble video showed sitting up more definitely helps onset wobble and leaning forward/downward settled in right down. Investigating weavy wobbles is a hobby of mine and find as front wears I have to ease air off or hands off horrors on set at even 50's just to diddle jacket of flush a wasp out of helmet. I do not think anyone could tell if their rear tire so out of line is almost rubs swingarm, at least after 5 mph or so. I've tested than in 2 Combats now. If forks are not free to swing that gets nasty too with a bounce to sides feeling even holding on good. Fork striction feels about the same but assume those ain't your issue at all.

The tires are year old Avon's with around 600 miles on them. The air pressure in the tires are spot on (my first thought as well).

When I torqued the bolts back together on the front end, I started from the bottom and worked my way up (compressing the forks after each torqued bolt). I do, however, remember having a heck of a time getting the axle back in (getting it out too for that matter).

nortncom said:

The tires are year old Avon's with around 600 miles on them. The air pressure in the tires are spot on (my first thought as well).

When I torqued the bolts back together on the front end, I started from the bottom and worked my way up (compressing the forks after each torqued bolt). I do, however, remember having a heck of a time getting the axle back in (getting it out too for that matter).

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The axle should slide in easily usually by hand or with a very light tap with a soft hammer.

If the damper rods have been fitted into the top nuts at different depths, that can affect the effective length of each fork.

Take the front wheel out and slide the axle into the forks. You should be able to see if one fork is longer than the other as you try to push the axle in. If there is a difference, estimate how much needs to be changed and make that adjustment by screwing or unscrewing a damper rod in the fork top nut.

best suggestion goes to Pommie John's above ^^^

the fact that you had a problem getting the axel to slide in shows the damper tubes are not equalized

Most headshakes start at the rear. Grab the rear wheel and shake hard left and right. See what movment you have in the ISO's.

If you're sure the forks are fine after you check them as others have suggested, I personaly would suspect the new bars. Screwy sounding as it may sound at first, clubman bars give you very little leverage compaired to European or other wider type bars and any smallish issue, tire wear, pressure, or I suppose alignment and even weight distribution that could be kept at bay easily with the additional leverage wide bars provide may now be the cause. Without any real input, just your hands resting on wide bars will do a lot to dampen osillations.

I wonder if this guy ever figured out his problem?
I'd be interested in knowing what was the cause.

My axle was hard to fit to my bike, triple clamps where bent,either that or fatten up