Author Topic: Steering shimmy? (Read 7292 times)

Kev Murphy · « **on:** July 11, 2015, 07:56:41 PM »

A new vibration. Comes in above 75k, shimmy is worst at about 90k. Unsettling, as I have to ease off before it becomes a tankslapper.
Happened after a hidden pothole impact. Forks undamaged and true.
Front wheel balance tested, and it's not that. Any other ideas?

Kev Murphy · « **Reply #1 on:** July 11, 2015, 08:00:04 PM »

I need a fast fix for this one, as it's only a week away from RTE in SA

ST2UP · « **Reply #2 on:** July 11, 2015, 08:07:45 PM »

Hmmm......it does sound like tyre damage, but you have checked balance

Happened to me on my 1100 a few years ago......had a wheel weight on the rim that I didn't know was there in the first place.....but I could see where it was and replaced, fixed the issue

Kev Murphy · « **Reply #3 on:** July 11, 2015, 08:09:52 PM »

Front tyre is only about 50% usage... had a dynamic balance test this afternoon, where the wheel is spun up to speed as well

ST2UP · « **Reply #4 on:** July 11, 2015, 08:12:08 PM »

Quote from: Kev Murphy on July 11, 2015, 08:09:52 PM

Front tyre is only about 50% usage

A big hit could have damaged the cords

Kev Murphy · « **Reply #5 on:** July 11, 2015, 08:14:44 PM »

Will remove tyre on monday, and check it internally for damage.

StinkyPete · « **Reply #6 on:** July 11, 2015, 08:37:09 PM »

It does sound like wheel balance.

Kev Murphy · « **Reply #7 on:** July 11, 2015, 10:09:15 PM »

close-up visual internal inspection may tell me more, but it's odd that it passed a dynamic wheel balance, where the wheel was run up to 130 KPH and showed no problems? 20 minutes later on the road, and the wobble was still there.

STroppy · « **Reply #8 on:** July 11, 2015, 10:27:34 PM »

Did they check the wheel itself for any out of true or a slight flattening or the rim slightly out? Might be worth looking at the bearings as well . .

Kev Murphy · « **Reply #9 on:** July 11, 2015, 10:50:25 PM »

yep, Stroppy, rim is true and no malformation. Bearings were pulled and checked as well.

STroppy · « **Reply #10 on:** July 11, 2015, 11:16:59 PM »

I wonder if one of the fork shocks valving may be slightly different to the other as a result of the hit?

HOFFY · « **Reply #11 on:** July 11, 2015, 11:22:10 PM »

I would start checking the front shocks.

My old CB750 ran for years without any problems and then one day the handle bars started to wobble at low speed and gradually got worse at higher speed.

It wasn't until I took the front end apart that I noticed that one shock was softer than the other and when you compressed the shock, it didn't compress smoothly. No obvious seal leaks.

Took both forks to the doctor and the internals of the shock were inspected and new oil added. Problem fixed.

Just a thought.

Good luck

Just a thought

Kev Murphy · « **Reply #12 on:** July 11, 2015, 11:27:49 PM »

Now that's logical, will have them checked on Monday... Thanks to all for the advice!

Kev Murphy · « **Reply #13 on:** July 13, 2015, 05:40:41 PM »

All becomes clearer after strip down of front end today.
Stroppy and Hoffy were on the money.
Left front fork has internal injuries, very little damping effect, its more like a pogo stick.
Also bottom head stem bearing cage has collapsed, and bearings are all to one side so the steering geometry is a bit kakky skewfonkered. Unsure if parts will arrive before the weekend, but can't book it into the bike shop until next Monday. Looks like I have to reluctantly cancel run to Swan Reach RTE next Saturday.

Kev Murphy · « **Reply #14 on:** July 16, 2015, 05:26:04 AM »

NOT very keen on this enforced walking caper during this lousy wet weather but on the high side, all parts required have arrived at bike shop and ready for installation Monday.

spanner · « **Reply #15 on:** July 16, 2015, 08:34:57 AM »

I wonder if that is why my beast is constantly wanting to go left.

I changed the tyres the other month but when I take my hands of the bars the beasties not so slowly veers to the left.

Hmmmm ..... what to do and who to see about that I wonder.

STroppy · « **Reply #16 on:** July 16, 2015, 09:21:42 AM »

Quote from: spanner on July 16, 2015, 08:34:57 AM

I wonder if that is why my beast is constantly wanting to go left.

I changed the tyres the other month but when I take my hands of the bars the beasties not so slowly veers to the left.

Hmmmm ..... what to do and who to see about that I wonder.

First thing I would check would be that the fork staunchens were located identically in the triple clamps . . If they are marginally different, it could result in veering to one side or the other . .

Wombat · « **Reply #17 on:** July 16, 2015, 10:25:38 AM »

The description is harmonic. Either bearings or wheel not aligned. There is a method for aligning the front wheel with the right pinch bolts I think. Will need to look at manual or STOC have an article I am sure
Cheers

tding · « **Reply #18 on:** July 17, 2015, 06:43:17 AM »

If the axle bolts were tensioned following the incorrect procedure can cause this problem. Have had it happen to me after having tyres fitted to a NT700v problem was that the tyre fitter missed the step where you bounce the forks three times to settle everything into position.

Kev Murphy · « **Reply #19 on:** July 20, 2015, 08:32:33 PM »

Bike is back on the road as of 6 pm tonight. Rebuilt front forks, seals, o rings etc. Visual inspection of tyre shows no abnormalities, inside or out. Head stem bearings replaced, and it now behaves on the road, no shimmy.
(all I have to do now, is budget to pay for it all, lol)

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Author Topic: Steering shimmy? (Read 7292 times)