ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-16-2010, 08:37 AM   #1
davemon OP
High Speed Airhead
 
Joined: Jun 2007
Location: NC
Oddometer: 112
Airhead tank slapper

Just did a 1200 mile ride on my 1977 R100S loaded with gear and camping eq. on the ride down road like a champ. Added my coat and riding pants onto the gear in the back and at 25 MPH the handlebars flapped like the tire was square. Repacked the load and same thing just not so bad. Was able to accelerate through the slap mode and cruised fine at highway speed. Made it home removed the load and same dance at low speed. Had the forks rebuilt about a year ago new rear schocks and new tires. Anyone else had this problem? Whats the fix?
Thanks
Dave
davemon is offline   Reply With Quote
Old 03-16-2010, 08:55 AM   #2
jtwind
Wisconsin Airhead
 
jtwind's Avatar
 
Joined: Nov 2004
Location: Madison WI
Oddometer: 3,473
My r80 with an S fairing did this. Not uncommon on airheads with handlebar or fork mounted fairings and windshields. On mine it was steering bearing adjustment that fixed it. But could as easily be the fork, tires, tire pressure, fairing or windshield attitude, poor shocks or loading/weight issues. I'd just work on making sure each one was right and then move on to the next if it doesn't seem to improve.

If you rode it similarily loaded before you did the forks, shocks and tires and it didn't do this, I'd start there.
__________________
JT

www.northwoodsairheads.com
www.jefftrappwindsors.com

"Between two explanations, choose the clearest; between two forms,
the most elementary; between two expressions, the shortest."
Between two motorcycles the simplest (DW)
Eugeni d' Ors (1881-1954); Spanish writer.


jtwind is offline   Reply With Quote
Old 03-16-2010, 09:00 AM   #3
Foot dragger
singletracker
 
Foot dragger's Avatar
 
Joined: Dec 2006
Location: chico,just below rag dump(nor-cal)
Oddometer: 12,818
The local BMW dealer is an airhead guy,he helped me put new races and bearings in the steering head on a R75/6 I brought back from the dead,he really stressed the adjustment on the steering head bearings. He used a torque measurement device suggested by BMW. He also said my forks would never work rt with out expert assembly and new stock parts.
Evidently the ft end on these older beemers is touchy about adjustment so maybe check all that over closely.
__________________
Some bikes around at times
Foot dragger is offline   Reply With Quote
Old 03-16-2010, 10:09 AM   #4
BKMLWR
Wondering around...
 
Joined: Feb 2009
Location: North Carmel
Oddometer: 4,530
been riding a 77 R100s since I bought it new in 77, over 170k miles never had a tank slapper except for hitting washboard road once, riding includes 2up cross country trips

Check tire pressure and steering head brgs
BKMLWR is offline   Reply With Quote
Old 03-16-2010, 11:20 AM   #5
Bigger Al
Still a stupid tire guy
 
Bigger Al's Avatar
 
Joined: Oct 2004
Location: Auburn, CA
Oddometer: 7,862
15 years on an R90/6, and the only time the front wags is when the tire reaches the end of it's life span. Once the shimmy begins, I replace it and things go back to normal. This is irrespective of brand or tread.

Still a good idea to check out the bearings, though.
__________________
"I'd rather wake up in the middle of nowhere than in any city on Earth."

Steve McQueen




Bigger Al is offline   Reply With Quote
Old 03-16-2010, 02:25 PM   #6
chasbmw
Beastly Adventurer
 
Joined: Feb 2006
Location: Bath Uk
Oddometer: 2,042
low speed wobble is almost always caused by too loose steering head bearings, move the adjuster nut in small increments until the wobble goes away, but not so much that the bike feels as if you have wound down a friction steering damper.

Charles
chasbmw is offline   Reply With Quote
Old 03-16-2010, 02:33 PM   #7
dilandau
Studly Adventurer
 
dilandau's Avatar
 
Joined: Aug 2009
Location: oakland, ca
Oddometer: 743
Quote:
Originally Posted by chasbmw
low speed wobble is almost always caused by too loose steering head bearings, move the adjuster nut in small increments until the wobble goes away, but not so much that the bike feels as if you have wound down a friction steering damper.

Charles
what he said - at least that fixed my wobble. the adjuster nut and the top nut sort of work together to make a friction damper so in my experience it was a bit of trial and error, moving the adjuster nut, then tightening the top--- testing how that was, then doing it again and again- maybe 4 or 5 times until it felt firm but the front end moved easy and smooth side to side.
__________________
morini 3.5 strada & sport, r75/6, duc 900sd (project)
dilandau is offline   Reply With Quote
Old 03-16-2010, 09:33 PM   #8
anonny
What could go wrong?
 
anonny's Avatar
 
Joined: Mar 2007
Location: Beautiful Revelstoke BC
Oddometer: 5,530
So.... how is your front tire? ..... check real close for cupping.
__________________
Kawasaki H1 build thread

71- 450 Honda CL re & re

Just another pathetic sheep following the herd

anonny is online now   Reply With Quote
Old 03-16-2010, 11:10 PM   #9
mphoppe
Hops
 
mphoppe's Avatar
 
Joined: Dec 2004
Location: Tucson, AZ - Dirt bike heaven!
Oddometer: 577
Steering head bearings...this is what fixed mine... follow the directions exactly....
http://www.largiader.com/bearings/
__________________
Mike

2006 1150 GS Adventure
2006 CRF 250X
2010 KTM 690R
1995 R100GS (sold)
2007 XR650R as new, for sale
2001 XR650R Desert Bike
2006 KLR 650 Commuter (Sold)
2004 XR650R (sold)
2002 XR650R (sold)
Pro Racing Photos http://mikephotos.smugmug.com/
mphoppe is offline   Reply With Quote
Old 03-17-2010, 02:37 AM   #10
BadBob
Riding or paddling
 
Joined: Oct 2008
Location: Any empty French road
Oddometer: 14
Tank slapper!

Yo Dave, nature of the beast!

Airheads, untill you`ve felt it, you would not believe!

Mainly because of the engines design.

The airheads are VERY intolerant of ;

Tyre wear/adjustment

Headstock/swingarm adjustment

Any loose frame/rack bolts!....one loose bolt on my rack, while touring in France. Tank slapper so bad, thought my frame had broken!

If you look at the position of the headstock relative to the rest of the frame, (with the tank off)

Its no wonder they somtimes shake there heads!

I welded two tabs on the frame, and attached a strut, on each side. (as I`d seen on endurance BMWs)

If you hold a inch dia. tube in position without removing anything.
just under the tank at the front. just above the S/Arm at rear. Its clear where to attach.

The change in handling is astounding!

From BMW to Italian motorcycle!!!

Ride safe, roll on summer!

BB
BadBob is offline   Reply With Quote
Old 03-17-2010, 03:21 AM   #11
davorallyfan
Commonist
 
davorallyfan's Avatar
 
Joined: May 2005
Location: Capitalist
Oddometer: 15,840
BMW's like yours are bad handling things and extremely sensitive to front tyres - change out - check pressures - my 90S was a shocker - I used to change out half worn front tyres to make it handle - ME33's.

They came with dampners but..

A new tyre should fix it steering head bearings - yes but its usually front tyre related
__________________
7th Day Adventourist.
Re-incarnated
Terrafied
davorallyfan is offline   Reply With Quote
Old 03-17-2010, 08:51 AM   #12
slash5swb
n00b
 
Joined: Dec 2009
Oddometer: 1
To get the steering head adjusted right, you have to lift the bike so the front end is hanging free. Starting with the wheel in the straight ahead position, you start to push the bars to one side or the other (doesn't matter which direction.) As you start to push, the bars front wheel should gently and slowly fall the rest of the way to the steering stop. This slow fall represents the right amount of friction from a properly tightened steering head. If the wheel falls quickly and bangs to the stop, it's too loose. if the wheel won't "fall" over on it's own (you have to push it all the way to the stop) it's too tight. It might take several adjustments to get it there, but it works, and it will make the front end very stable. (NOTE: Try to account for cables and wires that impede movement. Test fork in both directions and try to account for this in your estimation.)
slash5swb is offline   Reply With Quote
Old 03-17-2010, 12:09 PM   #13
charliemik
Gnarly Adventurer
 
Joined: Aug 2007
Location: Flagstaff AZ
Oddometer: 420
When you're tweaking the steering brg adjustment, you'll know you've gone too tight if your bike starts to do a slow weaving back and forth on the road.
__________________
"Knobby tires and a GS do not a dirt bike make" - from Coco's sign-in book.


'81 R80G/S-SOLD (sad but I think the new owner is a really happy guy)
'81 R100RS
'96 R1100GS
'83 VW Westfalia (my 4 wheeled adventuremobile)
charliemik is offline   Reply With Quote
Old 03-17-2010, 12:12 PM   #14
Wirespokes
Beemerholics Anonymous
 
Wirespokes's Avatar
 
Joined: Jul 2002
Location: Jackson's Bottom Oregon
Oddometer: 8,035
Quote:
Originally Posted by slash5swb
To get the steering head adjusted right, you have to lift the bike so the front end is hanging free. Starting with the wheel in the straight ahead position, you start to push the bars to one side or the other (doesn't matter which direction.) As you start to push, the bars front wheel should gently and slowly fall the rest of the way to the steering stop. This slow fall represents the right amount of friction from a properly tightened steering head. If the wheel falls quickly and bangs to the stop, it's too loose. if the wheel won't "fall" over on it's own (you have to push it all the way to the stop) it's too tight. It might take several adjustments to get it there, but it works, and it will make the front end very stable. (NOTE: Try to account for cables and wires that impede movement. Test fork in both directions and try to account for this in your estimation.)
Exactly! With one hand I hold the front of the fender and the other a handlebar. Then turn the front end slowly and feel for either too much free play or notchiness. Yes, notchiness! Too tight and it'll feel like bad bearings.
__________________
Wanted: Dead, smashed, crashed or trashed gauges
BMW GAUGE REPAIRS - TACH*SPEEDO*CLOCK*VOLT METER *PODs & LIGHT BOARD*
Wirespokes is offline   Reply With Quote
Old 03-17-2010, 01:09 PM   #15
P B G
Beastly Adventurer
 
Joined: Mar 2008
Location: Greater Chicago
Oddometer: 10,001
Quote:
Originally Posted by slash5swb
To get the steering head adjusted right, you have to lift the bike so the front end is hanging free. Starting with the wheel in the straight ahead position, you start to push the bars to one side or the other (doesn't matter which direction.)
And when you tighten it up the top nut will change things a bit.
P B G is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 10:56 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014