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#25141 - 05/22/07 9:22 pm front forks dancing  
Joined: Oct 2006
Posts: 3,017
Bob S Offline
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Bob S  Offline
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, Lower -Lower michigan
the other day i brought my a-65 thunderbolt 70, down to pull in the drive way. it wanted to shake alittle at quick slow down.not a wobble.kinda of a a something ain`t tight, shake. any clues


Bob S
Street Rods, Kustom Kars,A BSA,Cushmans,H.Shadow ACE, Now a 2004 triumph america . "More than enough!!!!
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#25142 - 05/22/07 9:31 pm Re: front forks dancing  
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Gunk Offline
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43.34 (4320') | -79.81 (-794...
brake drum out of round?
Worn out linings?
Was there a sound?


"he who laughs fast, laughs first"~Gunk
#25143 - 05/23/07 12:07 am Re: front forks dancing  
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Bob S Offline
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Bob S  Offline
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, Lower -Lower michigan
no sound---------just felt like.it was like jumping front to back [tire]in the forks under the pressure, of stopping; again not a wobble. confused


Bob S
Street Rods, Kustom Kars,A BSA,Cushmans,H.Shadow ACE, Now a 2004 triumph america . "More than enough!!!!
#25144 - 05/23/07 12:14 am Re: front forks dancing  
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Bob S Offline
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Bob S  Offline
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, Lower -Lower michigan
maybe it was ,like you say gunk,new brake shoes,grabbing sanded down, scuffed up drums,i`m befuddled


Bob S
Street Rods, Kustom Kars,A BSA,Cushmans,H.Shadow ACE, Now a 2004 triumph america . "More than enough!!!!
#25145 - 05/23/07 12:32 am Re: front forks dancing  
Joined: Apr 2005
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Adam M. Online content
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Adam M.  Online Content
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Mississauga, Ontario.
Worn sliders in the front end.
I have the same problem.

Adam M.

#25146 - 05/23/07 12:39 am Re: front forks dancing  
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Gunk Offline
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43.34 (4320') | -79.81 (-794...
You and I are connected thru space/time continuum man.
I have a problem, you have the same one, It's like the bikes we are working on are identical... well I guess they are in a way.
Did you have the wheels re-laced?, new rims?
I am told this almost always means the drums have to be turned.
This is how it happened to me.

AND, after they are turned, it is a good practice to sand the linings to fit the drums, with sandpaper held to the drums with plain old rubber cement, you spin the wheel and apply light pressure till the shoes are evenly scuffed. This matches the diameters of the linings and drums.
THEN, chamfer the ends of the linings about 1/2 their thickness tapering off 1/2".

Otherwise the linings can sort of "cam" in the drum leading to brake chatter.
It's like a sprag clutch:
http://www.epilogics.com/md/tekintro.htm

No point in doing this unless the drum is round.
You could check the run-out with a dial gauge if you have one, the only other way to know is if the brake is grabbing once every revolution.

I'm right in the process of shaping my linings tonight. I need a big wrench to get that spindle nut off, so I'm off to Crappy Tire.

This is the last big job I'm doing this year, I swear to God.

Tomorrow we ride.

PS. It could also be oil or grease contamination of the linings


"he who laughs fast, laughs first"~Gunk
#25147 - 05/23/07 12:45 am Re: front forks dancing  
Joined: Aug 2001
Posts: 3,348
BONZO R.I.P. Offline
In Remembrance
BONZO R.I.P.  Offline
In Remembrance

Joined: Aug 2001
Posts: 3,348
Michigan, USA
May also be loose steering head bearings, but if handlebars feel right while front wheel seems to rol under, I' suspectthe sliders/bushes as well . You might wanna set it up on the center stand and give it a wiggle. if I am not mistaken there is some good info on troubleshooting these forks in the factory manual.
FWIW-BONZO

#25148 - 05/23/07 12:45 am Re: front forks dancing  
Joined: Oct 2006
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Bob S Offline
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Bob S  Offline
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, Lower -Lower michigan
thats it, thats it------brake chatter,exactly,i gotta quit building cars. i got another top ten position, at alittle show[275]cars, and at home i`m forgettin how to do things, it stinks, this gettin feeble minded.i better calm down or i`ll have a stroke and have to give my 70 bonne away,------------------never happen. thanks gunk. :rolleyes:


Bob S
Street Rods, Kustom Kars,A BSA,Cushmans,H.Shadow ACE, Now a 2004 triumph america . "More than enough!!!!
#25149 - 05/23/07 1:50 am Re: front forks dancing  
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Gunk Offline
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Gunk  Offline
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43.34 (4320') | -79.81 (-794...
Worn fork bushes could cause this gents, but I seem to remember that Bob replaced his bushings and then had a problem with no fork movement.

And I suspect the steering head bearings would cause a bit more noise... I could be way off here.

I just did my brakes, started at 8:39 and finished at 9:45 including a trip to the store. Not bad.

I used to be able to replace my timing chain on my 74 Plymouth Fury in 45 minutes, can't for the life of me remember why I got so good at it.


"he who laughs fast, laughs first"~Gunk
#25150 - 05/23/07 2:30 am Re: front forks dancing  
Joined: Oct 2006
Posts: 3,017
Bob S Offline
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Bob S  Offline
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Joined: Oct 2006
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, Lower -Lower michigan
i rebuilt the forks, all new seals, o rings,,but---the nylon bushings i don`t think i did, they looked and slid quite well, when moving the two outer and inner tubes thru there travel. but i diD remember somE healthy scratchs in them. the top nuts were loose, tightened those.man--------why is it always the one thing you don`t do. that comes back to haunt you. do those top nuts need to be super tight?


Bob S
Street Rods, Kustom Kars,A BSA,Cushmans,H.Shadow ACE, Now a 2004 triumph america . "More than enough!!!!
#25151 - 05/23/07 2:55 am Re: front forks dancing  
Joined: Oct 2003
Posts: 11,109
RF Whatley Online content
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RF Whatley  Online Content
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North Georgia, USA
Quote:
Originally posted by BONZO:
May also be loose steering head bearings...
I was just about to say that. Loose head post bearings can happen for many reasons and they give a low speed shudder and lack of stability that's hard to pin down. Even with a perfect brake drum and rim truing.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#25152 - 05/23/07 3:01 am Re: front forks dancing  
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Gunk Offline
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Gunk  Offline
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43.34 (4320') | -79.81 (-794...
The top nuts don't need to be really tight.
The huge thread with the small pitch would make it darn near impossible for them to come loose.

Nylon Bushings?
There is a plastic, possibly nylon, collar between the upper and lower brass bushings. It's actually an oil retainer for the rebound damper. Scratches won't matter. Did you replace the brass bushings?
Or were they ok?
With the bike on the center stand, stand in front of the bike and try to roll the front wheel forward and back. If there is a clunking or looseness in the forks you will see it this way.


"he who laughs fast, laughs first"~Gunk

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