1982 R100 fork spacer dimensions

[Warm_Feet]

PLEASE HELP! I've just dismantled my 1982 R100 forks (Brembo calipers type) to find the top and bottom spacers are missing. I've tried to obtain some from MotorWorks, Motobins and James Sherlock without success. They will be simple to make on a lathe if any kind soul could give me the dimensions and state the material (presumably steel or aluminium?). The forks are what the Clymer manual calls type III. In my manual they are shown in figure150 on page 493 and are part numbers 24 (bottom) and 12 (top). If you have similar forks apart at the moment PLEASE measure your spacers and send me the dimensions. Better still, if you have any redundant ones lying around (not sure why you would) there's a contribution to your beer fund awaiting you if you're willing to part with them. Please help! Thanks

[Kurt in S.A.]

Welcome! I don't know about bottom spacers...seems like these are required "bumpers". But the top spacers might be made according to each rider. I think people have made PVC spacers to drop in. I think the idea is that this controls the sag. My dim recollection is that when sitting on the bike, feet off the ground, the sag is about 1/3 of the total fork travel. I've seen Tom Cutter write that the sag should be about 26-40mm of sag. I guess that means start the measurement with the front wheel off the ground, carefully put it back on the ground, then sit on the bike.

Kurt

[Warm_Feet]

Thanks Kurt, that's a help. I'm sure the bottom spacers are essential as without them the damper rod supports covers the oil change drain holes, so hopefully someone will come forward with the dimensions. But thanks again for your input, it's nice to get a response.

[Kurt in S.A.]

Aren't the bumpers at the bottom parts that can be ordered from any dealer? MaxBMW in the eastern US? Motobins in Europe?

Kurt

[Warm_Feet]

Hi Kurt, the rubber bump stops were fitted in the earlier ATE forks. Mine are the later "Mark III" forks with Brembo calipers. The bottom spacers must be incompressible (steel or aluminium) otherwise the fork oil would leak out around the damper fixing bolt each time they were compressed. I assume a previous owner wanted to lower the ride height, but I'm 6ft and really want the extra ground clearance when cornering.

[SteveD]

Which numbers? This diagram covers 9/80-11/82.

[Warm_Feet]

Part number 18 is the missing bottom spacers ring. The top spacer is not shown in this diagram, but is shown as part 12 on page 493 of my Clymer manual

[Rob Frankham]

From the BMW parts list...

Item 18 above - This part is not installed on the vehicle specified. I believe that item 24 on the Clymer diagram is actually the part numbered 9 on the BMW diagram above and is the part shown in image 156 in the Clymer manual.

Item 12 on Clymer - This part is a spacer ring to lift the front of the machine. It wasn't fitted to all models, mainly to those with full fairings to counter the weight of the plastic and restore the steering geometry. Also shown as 'This part is not installed on the vehicle specified'. Many riders fitted it to 'naked' machines in the belief that it would increase pre load... which it doesn't do, it just lifts the front of the machine (and incidentally, slightly reduces travel of the forks).

Beware using the Clymer manual as a quotable reference when referring to parts online. There are a number of versions of the manual around and these will have different page numbers (and probably illustration numbers). The same goes for Haynes manuals. MaxBMW or RealOEM sites are your friend here since they are available to everyone and actually mirror the BMW parts ordering system diagrams.

Rob

[Warm_Feet]

Hi Rob, thanks for your post. Part number 9 on the BMW diagram, variously called the piston ring or guide ring, is part number 17 in figure 150 page 493 of my Clymer manual (I appreciate it may be different in different editions). The part I'm looking for the dimensions of is definitely part 18 in the BMW diagram. Does the first statement of your post mean you have information to say it was never installed on my machine? Nice photos by the way. Tim

[Warm_Feet]

OK, it seems I've been somewhat barking up the wrong tree, but perhaps not without some reason: it seems that the bottom spacer was never fitted to my unfaired 1982 R100, but was only fitted to some RT and RS models. A huge thanks to Rob for pointing me in the direction of the excellent fiche diagrams and subsequent parts data on MaxBMW.com, I hadn't come across this excellent source of information before but had relied upon Realoem, who don't supply as much information. I'd assumed that if a part wasn't listed it was because it was unobtainable/no longer manufactured, whereas, as Rob pointed out, it means it wasn't fitted to that particular model. Now for the excuses! I was convinced the bottom spacer ring must be an essential part of the fork damper mechanism as I couldn't drain oil from my left fork after removing the drain screw because the damper rod support covered the drain hole. I couldn't see why BMW would provide a drain hole and then cover it. Yes, I did wiggle a wire up the hole to see if it was blocked with crud, but just met the solid resistance of the damper support. The witness marks on both damper supports confirm that they almost totally cover the drain holes; this is just weird. I can only assume a small piece of crud was blocking the hole and I failed to dislodge it, and there is JUST enough hole uncovered to facilitate oil draining - weird! I've only had my R100 for a couple of years and never owned a BMW before. Therefore I'm fairly new to these weird and ....., well, just weird motorcycles. Thanks again to Rob, and to Kurt for the info regarding the fork sag and top spacer. I can now confidently put the whole lot together again and get out while we still have some sunshine here in the UK.