I've got a little head shaking going on

[chasbmw]

Mostly BMW speedos are about 10% optimistic, but this will vary according to tyre diameter, who put the needle on the speedo, has a PO changed the final drive gearing etc etc. Checking with a gps is good.

32 is IMHo too low for a Macadam, 36 might be better.

Head shaking on a closed throttle deaccelerating from about 40 mph is indicative of head bearings that are too loose, tighten them in increments of about 2mm, until the head shaking goes away. If the bike sways from side to side, then your head bearings are too tight.

[bbelk]

Awhile back I thought I noticed my R90 getting a little rubbery in the corners. I couldn't find anything lose or tight in the front end and a new tire, which usually works wonders didn't help. Truth is, it was so mild, I wasn't sure it was happening, but in the back of my mind, I knew it was.

So - loaded with gear for a week on the road, two friends and I made it through the Hill Country out to Del Rio and I no longer could convince myself it wasn't happening.

I won the flip and had a bed all to myself so I started googling. Bonus points for figuring out who these guys are who lost the flip.



Anyway - I found several posts that described "the rubber cow syndrome" that is fundamentally caused by too weak a frame, but it is dramatically increased by the BMW two part frame where the back is connected to the front with four, little bolts if said bolts are less than properly tight. In the morning I tightened those bolts. They were neither super lose nor super tight and I could not see signs of them slipping, but it made a world of difference.





Here are the pictures of the rest of that ride: https://picasaweb.google.com/1055118013 ... IDENov2011

[ME 109]

Haven't we seen that pic before? Like, 5 years ago?

OW! Cut yer toe nails will yer!

[Duane Ausherman]

It is your imagination that going a bit tighter made a difference. The rear frame section only holds up the shocks and seat. It has nothing to do with frame rigidity, or very little.

[bbelk]

It is your imagination that going a bit tighter made a difference. The rear frame section only holds up the shocks and seat. It has nothing to do with frame rigidity, or very little.

I do have a good imagination.

[Deleted User 62]

Same thing happened on my R90/6. Felt like riding a fish, wriggling down the road. Turned out was the subframe bolts were loose. I had given the frame multiple coats of paint, then assembled it using nylock nuts, torqued to spec. I assumed it couldn't have become loose, but there was enough movement to wear the paint between the parts, and then...

[bbelk]

Haven't we seen that pic before? Like, 5 years ago?

OW! Cut yer toe nails will yer!

It was two years ago, but my memory is gone and all I have left is my imagination.

[Scoots]

Tomorrow, I'm bringing the '89 R100RS in to the BMW shop for new tires mounted and balanced - Michelin Pilot Activs, 90/90-18 on the front and 120/90-18 on the rear.

What I've been able to determine is that the slight head shaking I've noticed is only upon deceleration at around 40mph.

If the head shaking continues after the new tires are mounted I'll probably need to tighten the steering head bearings a little bit. I'll need to purchase a socket to mount on my torque wrench for the "top stem nut", which measures 36mm with my calipers. Would 36mm be the correct size socket, or am I way off?

THANKS for everyone's input!!! I've really been learning a lot!

[Duane Ausherman]

I suggest that you watch the balancing procedure carefully, as I have never been witness to a shop properly balancing a BMW motorcycle wheel.

[Steve in Golden]

I suggest that you watch the balancing procedure carefully, as I have never been witness to a shop properly balancing a BMW motorcycle wheel.

Not even your own shop?