twitchy

Hi all , my Mark II is " twitchy" over 100km/hr .. like its trying to get itself into a speed wobble all the time .. vernier isolatics set OK, swing arm bushes OK running 360/19 K 81 front K81 425 /18 rear ( 18 inch wheel came with bike) any suggestions? was going to try Norvil head steady.. not too keen on steering dampers? tyres maybe ?

thanks Greg

Hey Greg,
How old are the shockies? Lindsay had similar problems, made his arse cheeks go real tight coming home from Wanneroo the other month so changed shockies and fixed problem.
Tim

Depends , 4.10 is normal front with that rear , is it just extremely toey .the 4.25 18 rear is good .
Thruxton Motorcycles 850 PR ran them , but clip ons . If youve wide bars and are hanging in the breeze it'd explain it .

Obvious steering had bearings checked . Rims checked true .Maybe your not going hard enough . :wink:
Though Id be wary , nylon Jap TT100s wernt a match for British , in the wet ( or under duress ) so front wash out
was a possibility if used in anger .

Id grab a 4.10 for the front . same Manufacturor as the rear . and / or fit narrowish flat bars ?

thanks tim/matt

rear shocks are pretty new konis so they should be OK Tim will go back to 410 front plus a new rear and see what happens.. and yes wide bars Matt anyone fitted a norvil head steady and recommend???
greg

Hey conkey you have probably checked already but have had top head steady rubbers sepperate between metal and rubber can be a bit hard to see under tank Or maybe cush drive rubbers on back wheel flogging out swingarm bushes ok If there ok I'd look at tyre out of round if you want a hand Have spare tyres you can fit to fault find send a message best of luck with it good suggestion about shockies have spare shockies if ya need to try

thanks for the offer of the re shocks renorton.. but will try some new tyres and go back to 410 front and see where I get .. wouldn't think it would make a lot of difference but that day of the Norton ride it was particularly noticable when I had those two go pro cameras set up on the top fork york ???
you local guys coming acroos for a chrissy drink at the Jarrahdale Pub 11/12 ? \greg

. I recon youre hanging on to tight actually . . . :shock:

IF the Tyres real ones , dont panic . Unless you like drifting dragging the pegs , a pillion would steady it up .

The 3.60's dropped the nose a notch , steeping steering and reduceing trail . 1/10 of 5/8 of stuff all , near 750 settings .

Stock rear spings are vaugely 145 Lb , or is that the memory . The Goiling Gas skocks on mine came with 110 Lb springs .
So the front felt stiffer . 110 springs are plenty for solo , or two up ,. For around 10 stone rides ( Weight not Kawaskis )

The LIGHTLY resting the underside of the fingers on the bars , will probly see you seeing it differantly .
A automobile I put together weaved for two weeks , untill I steered with fingertips . Then Brilliant
for emulateing Ari Vartenen .or however you pronounce it . Used to take the paint of the gate post drifting in the driveway.
Without damadgeing the chrome on the bumper .

So there you are . with a butt stop taped to the seat and a decent knee grip and youre delicate fingertips , she'll hit a sixpence . Every time . ( Ran a 3.00 KR76 , I tried it ) If the elbows wobbled , it weaved, on the bumpy twisty bits .
Hanging on for grim death .Untill I used the Knees .One cant support oneself with the bars in such conditions . :wink:

Seen the olde Heim Joint top link ? ( Hobots post )

Matt Spencer said:

Though Id be wary , nylon Jap TT100s wernt a match for British , in the wet ( or under duress ) so front wash out
was a possibility if used in anger .

Click to expand...

During the 70's-80's there was a popular belief that Japanese tyres were 'made of Nylon' (because they often had "NYLON" on the sidewall) however that only referred to the internal ply cord material-not the rubber compound.

Hi Greg, I don't think the 18 inch front helps at all. As for the headsteady, I'd get one of Jim Comstock's jobs. excellent quality, works a treat. You've ridden mine and you know how well that steers.

By the way, I haven't had an e-mail since the big ride. Can you check your list maybe? Not long until I shift down your way. I'm really looking forward to it.

Your geometry is all wrong.
Do the following, & it will handle,
110-90-18 rear, 100-90-19 front.
Std. rear length shockers.
Fancy head steady.

I had the same problem for years with 18 inch front & rear.
You will find that 18 inch front & rear is alright 2 up, but goes to pieces when riding solo.

thanks all for the info .. Ken you should have recieved some emails from the Norton group??.. must have your email wrong.. best email me direct on gmcconke@bigpond.net.au .. with details on when you shift etc The rear wheel is 18 inch not front .. thats standard 19 but with 360 instead of 410. will try the sizes recommended on earlier post and see how we go
greg

You did check the swingarm spindle tube on the tranny cradle? They wallow out and produce the effects you are feeling. Drill and clamp-on fix available.

Put the bike on the centerstand, then see if you can wiggle the rear end assembly from side-to-side...

conkey said:

Hi all , my Mark II is " twitchy" over 100km/hr .. like its trying to get itself into a speed wobble all the time .. vernier isolatics set OK, swing arm bushes OK running 360/19 K 81 front K81 425 /18 rear ( 18 inch wheel came with bike) any suggestions? was going to try Norvil head steady.. not too keen on steering dampers? tyres maybe ?

thanks Greg

Click to expand...

Years ago I had something similar at a higher speed. I went through everything. Rebuilt forks, new shocks, new isos, oversize cradle spindle, with reamed bushings. I finally added a steering dampener. All to no avail. I eventually got around to replacing the rear tire from wear. Wobble gone! Whether it was the tire or mounting, I'll never know. Both tires were the same, Avon Super Venom.

conkey said:

Hi all , my Mark II is " twitchy" over 100km/hr .. like its trying to get itself into a speed wobble all the time .. vernier isolatics set OK, swing arm bushes OK running 360/19 K 81 front K81 425 /18 rear ( 18 inch wheel came with bike) any suggestions? was going to try Norvil head steady.. not too keen on steering dampers? tyres maybe ?

thanks Greg

Click to expand...

I would think it rather fussy adjusting wheel alignment with mismatched width tires, but that is an area to check along with pressures. Money might be more well spent matching up those wheel/tire.

Remove the tank and loosen the head steady bolts into the head. Sit on the bike as if riding (no stands) then snug up the bolt for proper alignment.

Tire pressures ? Had an inaccurate pressure gauge that confounded me until compared with a buddys. Then bought a better one.

conkey said:

thanks tim/matt

rear shocks are pretty new konis so they should be OK Tim will go back to 410 front plus a new rear and see what happens.. and yes wide bars Matt anyone fitted a norvil head steady and recommend???
greg

Click to expand...

Installing an aftermarket headsteady is probably the single best mod there is for handling. The setup on the Norvil headstedy is not as straightforward as it looks. A link type is much easier to get right and probably just as effective. Make that, infinitely easier to set up.

+1 on all the problems that the wrong riding gear, bars, and seat can create regarding handling. The first long ride I took on my bike was a 2500mi trip to British Columbia. I wore a baggy leather jacket, USA bars, and no bum-stop on an Interstate seat. The death grip I had to have on the bars just to keep from getting blown off the back accentuated every handling issue a Commando can have. It probably didn't help that the rear tire was worn to a square cross section half way through the trip. Still had the time of my live though

I'm stlll working up to my time of Commando life long term Bob. Combat Trixie was darn scary on her old worn out tires, twitching jumpy to hold much lean even on fair surfaces, now with NOS tires she a dream to swerve around even though I've still not put back her factory head steady yet. That can be a bit dangerous if not aware of it and cross paint lines or groovy pavement will start to hinge but otherwise very on rail feeling. This implies you can't really say how your Cdo should behave until on two new tires, then diddle with what ever for full joy and when that nice feeling decays suspect tires again and compensate till renewed. Can't wait to feel new tires security with head steady on. Don't even ask me about links help to top all this. I did have to play with fr/rr air balance to get the light steering feeling nice on these new tires which at first was disappoing annoying, thinking the hard old tires had less cruise ease resistance.