My son in Charlotte, NC has a 1974 R75/6 that has developed a wobble in the front. I am going there in a couple weeks, (end of the month) and plan on helping him cure this problem. I have never done one, so I am wondering what I might need to fix it. Like special tools? extra thin wrenches? Are there any tricks I need to know, like should the front wheel be elevated off the floor? Things like that. Thanks in advance for any input.
Sid, near Niagara Falls
I've done 2 BMWs from the 1970's now, and countless other Brit bikes, and I'm finding the same thing in all....
► The grease in the head post is usually oxidized to the point of leaving hard deposits on the steering head races (and all over the steering damper). It is necessary to remove the front wheel and drop the front forks. On my personal bike the forks never actually came off the bike, they simply got dropped about 4", enough to expose the lower bearing, which is usually where most of the problem lies. Unless you see lots of rust, I would not advise replacing the bearings. Wash and blow (high pressure air) both bearings and their races in solvent (like WD-40) until the old caked-on grease is all gone. Replace it with a water-proof grease, such as boat trailer wheel bearing grease. I tighten the top nut until the forks swing easily with zero play when yanking on the bottom of the fork legs. BMW may have a torque listed.
If you replace the races, riding the first 100 miles usually seats them deeper and a second bearing adjustment is always advised.
► Replace the damper. They are up to $91 now, but well worth the expense. Set the new one to position #2.
► Change the fork oil using a high quality motorcycle fork oil, such as BelRay. BelRay makes a 7W (equivalent of ATF), 10W and 15W. Try the first 2 for ride quality. The 16oz size will give you enough for 2 changes. Change fork oil at least once a year thereafter.
► Lube the front wheel bearings. Check for any play by grabbing the wheel top and bottom from the side and doing a push-pull. Zero play is acceptable.
► Know that ANY variation in the running of the tire's center groove is going to steer the bike, especially on concrete "rain grooves". So, is the tire running true and perfectly round? Does the rim need truing, or is the tire not fully "popped out" on the rim ?? Any discrepancy in the true-ness of the tire steers the bike. This is why sport tires no longer use a center groove. Consider mounting a modern Michelin Pilot or other 'centerless' tire, 100/90x19.
► Tire balance. The best static balancing is done with 2 naked bearings (no grease, absolutely clean, except for 1 drop of clean motor oil) supporting the wheel on the stock 17mm axle, NOT by using the wheel's own bearings. Even after that, when using a inner-tube you may wish to inject some liquid wheel balancer.
Those steps will cure 90% of all front end issues.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Sounds good. Thank you!
2 more items that might help...
As far as getting the wheel in the air.... I use an old scissor jack with a chunk of 2x4 affixed to the top.. You can place this under the exhaust cross-over without fear of leaving any marks. This works "a treat" on all types and brands of bikes.
Paramount to any work on the front end is initial diagnosis. Chief witness for the procecusion is the condition of the tire, and the aforementioned "run out" on the center rib or groove. If you see cupping then you know not enough attention is being paid to air pressure. (Correct air is critical for proper handling. I wouldn't dream of going for a ride without knowing my front tire pressure. It's that critical.) What many owners also fail to realize is that modern tires are running 4-6 psi more than the old owners handbooks quote.
Once cupping gets started, there is no way to stop it. You might as well commit to a new tire and a promise to be more diligent. And buy a really good tire pressure gauge too !!
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
I will do this when I get there, to see what the deal is. I suspect hard grease, but any of the other culprits might be present. I know I personally run my tires a bit on the soft side, after having run the center out of a few over the years., and I have even had some cupping on one once, but it did not cause any wobble that I could notice,
I see this post is 2 years old but I'm glad i found it. I have a 78 R100S. Not sure of the miles as the speedo had some issues before I got it 2yrs ago. I'm addressing my steering head bearing. When on the center stand I can move the forks back an forth a bit and there's a clunk from the forks going over bumps. I have the upper bearings exposed and the grease looks old but it's still grease not hard chunks. I'm gonna remove the front wheel and drop the forks as you said. Do you think, I can tighten up the forks so it won't clunks. The top nut with the 4 notches in it was pretty tight and the threads had hard grease/grime on them. It cleaned up easily enough but this may be the 1st time it's been opened up. My forks were frozen but I fixed that when I got it home 2 yrs ago...
Do you think I can tighten up the forks so it won't clunks.
I think you can load the bearings with new grease and set the pre-load on the steering head bearings per the manual to such an extent that it will rule out noise from the steering head bearings.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Thanks for your fast reply. Haven't even washed up yet. I'll hit it tomorrow. Preferred grease? Auto wheel bearing grease
Watched a video on this. If I'm doing the bearings then i should probably do the races too, right? It looks complicated with the special bmw tool. They chiseled off the bearing. I want to do it right but i think I'd need to take it to a shop to remove the chase and lower bearing. Maybe it's not that bad to do. I'll play tomorrow.
Well, i did the fix as you recommend. The bearings and races looked fine. Repacked with wheel bearing grease. And the clunk is gone! Thank you very much. I now know how to disassemble the front end and the proper sequence of assembly. Had to remove the fork brace times. Next time it's a 2hr job instead of 6. Again, thanks
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