Author Topic: Help with wobble please  (Read 1220 times)

Online Noguzznoglory

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Help with wobble please
« on: May 05, 2018, 07:14:19 AM »
I have been experiencing a pulse in the front brake on my 04 Breva 750, 7500 miles. Also, if I let go of the bars at 45 mph or above the fronts starts an increasing wobble that would eventually turn into a death wobble. Stops as soon as I grab the bars.
Bought the bike with 2k miles and the pulse in the brakes has been there since day 1. Wobble maybe. 
I donít find any significant runout in the front wheel or rotor.
Wher would be a good place to start looking. Steering head bearings?
93 750 Nighthawk
83  Ascot
04  Breva 750
10  NT700V
16  VERSYS 650

Online Rebochi

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Re: Help with wobble please
« Reply #1 on: May 05, 2018, 07:30:53 AM »
    What condition is the front tire?
1200 GS
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Offline M0T0Geezer

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Re: Help with wobble please
« Reply #2 on: May 05, 2018, 08:09:09 AM »
I have a 2004 Breva 750 with 56,000 miles on it.  I have had 20 other bikes beginning with a 1953 Cushman eagle.

Many of these bikes, including my Breva, have developed a front end wobble.

On every bike, every time, a new front tire fixed the problem.  Try it on your Breva.

I have always used these tires on my Breva, which I always replaced in pairs (even though the front was only half-worn). I am now rolling on my 8th pair:
F: 110/70-17 Pirelli Sport Demon = 110mm (4.3") Wide x  77mm (3.0") Tall
R: 130/80-17 Pirelli Sport Demon = 130mm (5.1") Wide x 104mm (4.1") Tall
"Guzzi recommends 36/36 psi for the Sport Demon"

The above tire specs came from the on-line Guzzi 750 fyi file which I curate.  There you will find other useful info:

  http://www.dansher.com/bikepix/Guzzi/_V7_fyi.txt

'Geezer
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Offline craigclu

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Re: Help with wobble please
« Reply #3 on: May 05, 2018, 08:33:07 AM »
Not as "Geezer" at 53 years of riding but I would echo all he provided...  I would add that I've tried running a bit higher pressure and that seemed to keep the wobble from starting in many cases.  Tire replacement always worked for me, too.
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Offline Bisbonian

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Re: Help with wobble please
« Reply #4 on: May 05, 2018, 09:34:51 AM »
As far as the brakes, some pads can leave deposits on the rotor which result in a high spot.
Perhaps a change of brake pads could help. 1200 Sports were notorious for this, changing to the EBC HH series pads was the ticket.

Offline M0T0Geezer

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Re: Help with wobble please
« Reply #5 on: May 05, 2018, 11:08:06 AM »
As for the pulse in your front brake:

Put the bike securely upright and get the front wheel off the ground so it can spin freely.

Carefully rotate the front wheel whilst "shaking" the front rotor firmly with both hands.  Repeat for six or so rotations.

The purpose of this manoever is to restore the rotor so that it again "floats" freely (very small amount of free play) on the little golden barrels that position the rotor to the front wheel hub. The is design functionality.

Sometime the rotor siezes onto the wheel (no free play) which can resut in pulsing on the front brake lever.

'Geezer
2007 Moto Guzzi Norge 1200 USA

My 65+ years of motorcycling here:

http://www.dansher.com/mywheels.htm

Wisdom from the road:

http://www.dansher.com/bikequotes.html

Play guitar or keyboard?  You will like:

http://www.dansher.com/audio/pdf_tunes.html

Offline gfritzmeier

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Re: Help with wobble please
« Reply #6 on: May 05, 2018, 11:32:24 AM »
Had a wobble at lower speed than you with my 03 Cal Alum.  New front tire took care of it.
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Offline Sasquatch Jim

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Re: Help with wobble please
« Reply #7 on: May 05, 2018, 11:44:30 AM »
 Tighten your steering head bearings a schoosh. With the bike on the center stand, put weight on the rear to lift the front wheel off the deck.  The steering should not flop to either side.  It should slowly turn to one side or the other with a touch to get it off center.  If it flops quickly to the side, the bearings are too loose and you are at risk of a tank slapper.  Very bad thing, it can wreck your bike and even kill you.  Tighten a little at a time until the steering does not flop to the side.  If you are running a sidecar this is especially critical and you should also have a steering damper.
 I adjust mine to no flop and I can take my hand off the bars at cruising speed. Then I install the steering damper for insurance. 
Sasquatch Jim        Humanoid, sort of.

Offline pressureangle

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Re: Help with wobble please
« Reply #8 on: May 05, 2018, 02:03:37 PM »
Tighten your steering head bearings a schoosh. With the bike on the center stand, put weight on the rear to lift the front wheel off the deck.  The steering should not flop to either side.  It should slowly turn to one side or the other with a touch to get it off center.  If it flops quickly to the side, the bearings are too loose and you are at risk of a tank slapper.  Very bad thing, it can wreck your bike and even kill you.  Tighten a little at a time until the steering does not flop to the side.  If you are running a sidecar this is especially critical and you should also have a steering damper.
 I adjust mine to no flop and I can take my hand off the bars at cruising speed. Then I install the steering damper for insurance.

Exactly. Your steering head bearings should be preloaded, but just enough to stop the fork from flopping to the stop by gravity. It's amazing what even the smallest amount of slack in the bearings can cause.

On the other note, some motorcycles are very particular about what tires they like, or don't like. It doesn't have to make any sense, but anything other than the factory shoes is a possible no-go. If the rear tire is not the factory tire, and a new front and bearing adjust doesn't make it go away, change the rear to a different tire and see if that fixes it. Unfortunately there is no inexpensive way to discover the root of a mystery wobble.
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Online Tom

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Re: Help with wobble please
« Reply #9 on: May 05, 2018, 04:32:15 PM »
 :1: on the front tire.  Put your air pressure up to near max on the sidewall.  Adjust steering neck bearings.  Check and adjust swingarm bearings.
There are no stupid questions.  There are however stupid people asking questions.

Online Noguzznoglory

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Re: Help with wobble please
« Reply #10 on: May 05, 2018, 06:15:04 PM »
    What condition is the front tire?

Good. 3000 miles, no cupping
93 750 Nighthawk
83  Ascot
04  Breva 750
10  NT700V
16  VERSYS 650

Online Noguzznoglory

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Re: Help with wobble please
« Reply #11 on: May 05, 2018, 07:23:50 PM »
The bike obviously sat more than ridden the first 12 years of itís life so the rotor suggestion may be the fix. Iíll check ALL the suggestions made.
I replaced the tires as soon as I got it with OE spec sport demons.
Thanks for all the help and suggestions.
93 750 Nighthawk
83  Ascot
04  Breva 750
10  NT700V
16  VERSYS 650

Offline stubbie

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Re: Help with wobble please
« Reply #12 on: May 05, 2018, 08:00:02 PM »
Just had a similar problem with my LeMans. Front tyre looked good but had waves in it. Run your hand along the tyre and check.

Offline jacksonracingcomau

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Re: Help with wobble please
« Reply #13 on: May 05, 2018, 08:17:52 PM »
Steering head bearings need a regrease anyway, inspect for notches, if all good regrease and adjust. If notched, even slighly, replace bearings.
Grease is 14 years old if there was much in first place.
I do it every other front tyre, havenít bought new bearings for at least 15 tyres.
Ditto the swinging arm bearings, just maintenance

Online pete roper

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Re: Help with wobble please
« Reply #14 on: May 05, 2018, 11:36:02 PM »
Small lock 750ís rarely have any grease in their steering head bearings. At this point theyíre almost certainly cactus. This may not be the sole cause of your problem but itís likely a contributor.

Pete

Online Noguzznoglory

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Re: Help with wobble please
« Reply #15 on: May 06, 2018, 06:24:28 AM »
Thanks again all!
93 750 Nighthawk
83  Ascot
04  Breva 750
10  NT700V
16  VERSYS 650

Offline wyno

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Re: Help with wobble please
« Reply #16 on: May 06, 2018, 07:05:34 AM »
I had a 2011 Breva and I had the same problem. Pete (Roper) replaced the bearings form and the problem went away.
Wyno

Offline MMRanch

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Re: Help with wobble please
« Reply #17 on: May 06, 2018, 09:15:45 AM »
  M0T0Geezer
Guzzi Mentor


I have always used these tires on my Breva, which I always replaced in pairs (even though the front was only half-worn). I am now rolling on my 8th pair:
F: 110/70-17 Pirelli Sport Demon = 110mm (4.3") Wide x  77mm (3.0") Tall
R: 130/80-17 Pirelli Sport Demon = 130mm (5.1") Wide x 104mm (4.1") Tall
"Guzzi recommends 36/36 psi for the Sport Demon" 


Mine came with these tires and the rear lasted almost 4,000 miles before it was "Way -Way down into the wear bars".   The 90 series I replaced it with made the speedometer and the GPS agree to what speed we are going !  :wink:


« Last Edit: May 06, 2018, 09:18:56 AM by MMRanch »
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Online Ncdan

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Re: Help with wobble please
« Reply #18 on: May 06, 2018, 10:55:21 AM »
After trying some of these obvious fixes and you still have an issue, maybe try a fork brace. Back in the early to mid 80s my PD used 900 Honda customs for police MC. We equipped them with Vetter fairing and bags. We had the same issue when hands were remain from the bars, all the other possible issues were attended to by the Honda dealership. It came down to placing a FORK BRACE on the bikes which fixed the problem. However we were instructed to keep at least one hand on the bars at all times....:)

Online nc43bsa

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Re: Help with wobble please
« Reply #19 on: May 06, 2018, 01:37:37 PM »
My Mille hasn't wobbled yet, but I've been interested in a fork brace.  I know how one helped my BSA while I was road racing.

Does anyone know of one that fits?  I'm not opposed to an old or used one.
1990 MilleGT

Online Muzz

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Re: Help with wobble please
« Reply #20 on: May 07, 2018, 02:54:02 AM »
Small lock 750�s rarely have any grease in their steering head bearings. At this point they�re almost certainly cactus. This may not be the sole cause of your problem but it�s likely a contributor.

Pete

Mine had bugger all grease in them.  Fortunatelycaught it in time. They had also come loose. Greasing and tightening made quite a difference to how the bike felt in the corners.

Mine has never shaken the head like that. I have always had a Sport Demon an the front so I don't think it is the brand of tire. I am wondering if it is the balance of the tire.
Muzz. Cristchurch, New Zealand
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Online Tom

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Re: Help with wobble please
« Reply #21 on: May 07, 2018, 06:24:29 PM »
The brand of tire has less of an influence than lower air pressure.  For bias-ply tires lower air pressure means more flex in the sidewalls.
There are no stupid questions.  There are however stupid people asking questions.

 


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