30 mph head shake

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maylar

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My '74 Norton has developed a nasty front end shake that's evident with hands off the bars between 30-35 mph. I've checked the front end and everything seems right. Tire is good (Avon Venom), wheel is balanced. It tracks well, no left-lean, takes road cracks without wandering.

The only thing I've done recently is to replace a headlamp bracket that got damaged in a light fall last year. I'm using the flat washer and have torqued the lower yoke nut per factory manual.

Any ideas?

Thanks
 
Don't think I've ridden one that doesn't do it. With my 2.5 inch x 19 rims and Avon Roadriders it's very much reduced to almost nothing but both tyres are overdue for replacement at the moment so it feels like a normal Commando. Hehe.
 
Check the front tyre is evenly mounted on the rim, there's a small bead runs round the tyre close to the rim use that as a guide.
Cash
 
Shop proven procedure - get everything (forks, wheel ) just snugged up and bounce the bike up and down with the front brake applied. This centralises the front end where it needs to be. Then torque up the top nut (clock bracket) first to seat the stanchion tube and then tighten the lower yoke pinch bolt. Check also that the front axle nut is torqued with the brake applied and then the left pinch bolt on the lower fork leg.

Mick
 
swooshdave said:
Mine does not shake.

Might be the headsteady.

+1 on checking your headsteady. Same thing happened to me many years ago...30 mph shake that scared the sh*t out of me...turned out to be a cracked HS.
 
Mine has the same head shake. ('74 850 Roadster)

I just got it out of the shop where the front wheel was taken apart and re-laced.

What is a "head steady"? Is this the headset bearing?

Thanks.
 
Not that I know anything, but something obvious that I forgot to check once was the tire pressure. Low pressure even on a great tire can make the front end do the mamba. +1 on the headsteady. Also, you mentioned a light fall- steering head bearings okay, no play in there? That's everything I know. Really, that's everything. Good luck! :-)
 
uGH all of the above. Tire wear and storage set profile and front to rear air balance are the most common reports I've read on excess shimmy to ride her down hands off. Some crashes can tweak the top steady and under brace tube w/o fracturing them. I've had floppy set driven and primary chain tugging help do this, especially when sleeve bushes shot so clutch basket wobbles, so changes drive chain tension so wags swing arm in its cradle and build to fork slapping state slowing down hands off. I've had jacket flap or cargo sticking out one side tend to do this too. Stuck restrictive stem bearings don't tend to do this but do tend to jerk you this way and that unexpected at each little road indention but its obvious the road texture as not a rhythmic build up.

My 1st clapped out pre-Peel Combat did this. My 2nd just new fixed everything but old k81 front tire Trixie Combat could toss me off coasting below 40 hands off, above that is steady to steer by body english. Ms Peel with all straight structures and rear rod would coast almost to stop before fork motion got floppy and had to grab back. Its handy to let go to zip up jacket or fiddle helmet and not fast fly off the edge or get slapped down. Not possible on Trixie unless over 50 and some time before slowing into 40's. Will watch this station for more insights involving only Norton components.
 
ML said:
Shop proven procedure - get everything (forks, wheel ) just snugged up and bounce the bike up and down with the front brake applied. This centralises the front end where it needs to be. Then torque up the top nut (clock bracket) first to seat the stanchion tube and then tighten the lower yoke pinch bolt. Check also that the front axle nut is torqued with the brake applied and then the left pinch bolt on the lower fork leg.

Mick

Yeah, that's what I did Saturday. I even rotated the fork tubes thinking that maybe they were worn a bit.

I've been noticeing a bit of low rpm vibration lately too.. will definitely check the head steady.

Thanks for the ideas, folks.
 
When I first got this bike it had the typical Norton low speed wobble if I took my hands off the bars. After rebuilding my hubs, new alloy rims/spokes and a new set of Avon tires and a CNW headsteady the bike was solid and had no wobbles. I could take my hands off at any speed & she was fine. Just noticed last month the low speed wobble came back & all I can think is it's due to tire wear. My back tire is orrery flat in the center. Nothing else has changed. I will get a new tire & see what happens.
 
I think you are correct. I just had two new tyres fitted on Saturday and mine has gone back to the point where there is only the slightest trace of the headshake at that speed. Normally i change the front to the rear and put the new tyre on the front but due to circumstances I haven't been able to do this so have run the same front with four new rears and they were both well worn when replaced. Again I have WM4 (2.5 inch) x 19 inch alloy rims with AM 26 Roadriders in 100/90 size. Steering and stability are truly excellent but it appears that I am the only one to run this combination, certainly on this forum.
 
Had this on a 750 and checked everything. Was worse with paniers fitted but better with a pillion. Changed to 18 inch 425 wheel/tyre combo and made no difference - cured eventually by renewing bearing in rear sprocket dunno why!
 
When I wrote about this below, under "The effects of a steering Dampener", I was more or less told I was wrong.
When mine had Std, 19" wheels & Std. headsteady it shook hands free at about 30mph, but otherwise was a very good handling bike, apart from the tankslapper at 110mph once when deccelerating into a bend.
Now with 18" back, 19" front & ISO headsteady it don't shake.
 
I am having the same problem on my 750 commando, 30-35 mph, nasty shaking going on. 19" tires front and rear all beaded up. I pulled the headstay this morning and found this:

30 mph head shake


Both sides are cracked. Hopefully getting this welded back up will take care of it.
 
You can buy a new boxed headsteady for about $60 here in the US, or Norvil has them for about £30 plus shipping, unless you have a cheap welder they would probably last longer.

Dave
69S
 
I have a buddy who can weld it up for free for me. He takes it to his work and knocks it out during his lunch.
 
Unfortunately knowing what I do now, it looks more like a quality chastity belt and function, fancy and well made as they might be, still a downer for smooth road orgasms. Why don't the owner maker use it instead of dumping on the un initiated.
 
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