slight wobble help

we did a lot, including removing, cleaning, re-greasing, and replacing steering head bearings. Would you expect the wobble particularly as I decellerate thru about 45mph @ about 4k is most likely caused by improper adjustment of that big top nut? Not as strong a wobble as I accellerate or try to maintain a speed in the mid-forties, and nowhere else up thru indicated 90 mph. Not affected much by changing the setting on the new damper. It's not a tank slapper, but both disconcerting and annoying. Could it be something else, like valves or carb synch? Lower fork brace?

They're brand new conti twins, balanced carefully etc. I'm mostly wishing it was something other than steering head adj because the PO installed two extra guages on the dash which make it a true pita to remove the dash and get at the adj nut. I'm thinking it's likely fine-tuning the steering head, but I didn't want to skip past other possibilities.

If I had to guess, I'd guess tighter. I saw recently where other people had written that looser was not a good idea, but both Ted Stroble and Seymour think the the front tire should "fall" from C to lock with just a slight nudge. Mine definitely falls. Maybe I need to tighten enuf to get it to require a stronger nudge.

BMW actually had a drag gauge to set the drag on the steering head bearings. Of course we don't have those in our tool boxes, so it's done by seat of the pants. The old rule of thumb was to accelerate up to 50 MPH and let go of the handlebars. If everything was as it should be no wobble. If there was a problem, (wobble) an adjustment was in need.FYI... Instead of taking off the handlebars to get to the large nut, use a grinder and take off just enough material from one edge of your BMW wrench so it'll pass over the large nut without interfering with the bars. Saves mucho time.

Woodgrain

thx. fifty's no prob' hands off, hands on. It's say 48 (indicated) down to 42 mph that's dicey, and way especially w one hand off the bars. That's entertainment.

I think "drag" is a good word for how the "fall" from L to R ought to feel. Mine needs a "hair" (metric) more drag.

And p.s. what would you say the bmw speedo is optimistic? ...6 Mph?

almost perfect

Thanx. We did that lift the forks for movement test, but only observed from the front as the forks were push-pulled. I bet if we watch the top while we're trying to move the forks we'll see a bit of play.

The oil temp and oil pressure guages look pretty cool and watching the temp guage periodically go crazy gives me an activity while I'm riding, but jeeez! what a pain in the nuisance thay make "little" jobs like this.

La guerre.

Wobble on decelleration is the classic symptom of loose SHB. It's not the big nut on top that's loose. It's the one between the top clamp and the frame that needs tightening.

On the centerstand with the front wheel not touching the ground, center the forks. Then tap one handgrip. They should NOT FLOP to the side. They should slowly fall to the side, left and right. Sometimes cables make judging it a little difficult.

Thanx. I think the movement on mine would be more accurately described as closer to "flop" than "fall". I bet one more tap on that nut and we'll be good to go slow.
Thanx.

better, but new issues

Took it all apart again yesterday. (It's less and less of a pita now that I know what really has to come off to get at it and what tools won't do the job) And yep, that pretty much did it. Tightened the steering head nut enuf to move our mark on the edge about 3/8 to 1/2 in, and w the damper set at the 2nd position it's fine.

Took unough time tho' that since the engine was cool I looked at the valves, and both exhausts had closed from .008 to about .004 after only 1500 mi. I don't expect to be able to put on a lot of miles this summer, so I think I'll just keep a close eye, say every 1000 mi, and do the valve work over the winter.

But despite, or maybe because of all the time, labor and money, I really love this bike. And the knowledge and confidence I've gained over the past couple months is a huge gift to an old fart. What a great group of people this bmw crowd is!

62 MPH is more like 55MPH according to something I read last week. BMW made/makes their speedos on the optimistic side.

Woodgrain

6mph to MN

somewhere in the distant past i seem to recall hearing about 6mph optimistic. it seems about right.

If I were desperate enough to go up to The Hiawatha in the rain this saturday and ride around a bit to boot, it'd be time to check those valve clearances once again. If they keep closing I think I'll try some imitation lead fuel additive.

..I think I'm that desperate...:+ = bliss

My /7 is spot-on in terms of MPH but I also tend to "drive the tach". I do the 5 mile timing run on the freeway at a constant speed to check my speedometer. I found that with the latest round of 110/90 tires on the rear, my speedometer began to read more or less accurately. I plan on going back to the 4.00 inch tire the next change, which will probably throw things off again...

woodgrain said:

62 MPH is more like 55MPH according to something I read last week. BMW made/makes their speedos on the optimistic side.

Click to expand...

A bulletin came out in 1996 and then was updated in 2002. Not sure if what was stated applies back to earlier models...probably does reflect general philosophy. What it stated was the speedometer advance (ie, indicated speed being faster than the actual speed) was necessary to compensate for negative tolerances in tire sizes, errors in the speedometer, and other general factors. The maximum amount of speedometer advance was to be 10% of the actual speed plus 2.4 mph. At 55 mph, this worked out to nearly 8 mph of advance or 63 mph indicated. That's pretty close to what woodgrain quoted.

I checked my speedo at 70-80 mph against a friend in a car and it seemed pretty close. My 78 r100s wobbles quite a bit from indicated 37-42 mph. I asked my tech and he said not to fool w/ SHB - it might fix, but chances were iffy - basically just deal with it (not really a problem as long as both hands are on the bars). talked to some other owners and most suggested tires - pirelli (sp?) were all mentioned as best, but i can't recall model. Iv'e read articles that indicate a good cleaning/tightening or replacing of SHB will fix problem, but for now i plan to wait until new front tire is needed (and I have a conti waititng to be installed). It does not seem to matter if i'm accelerating or deaccelerating, just that particular speed. Iv'e gotten used to not pulling down face shield at 40 mph, which is usual speed for me to lower it. I look at it as an idiosycrancy of a 30 yr old bike and just deal with it. No other speeds seem to have this effect.

Please advise if you find a solution.