Hello, I'm posting this here by request. Anyone please feel free to copy it to other lists/sites where it may help someone. I understand there is a specific list for the R100GS PD in the USA as well as in Australia. There may be others - I'm just too new to BMW's to know.

Several days ago, I posted a brief piece about getting ready to change the throttle cables on my 1990 R100GS. That piece dealt with the subject of "to lube or not to lube" - determined: "not to lube" - won the day.

With that question settled, I set to work pulling the new cables in with the old as per the recommendation in my Clymer's Manual. New cables in place, handlebar throttle assembly cleaned and lubed, I connected the new cables to the carbs. It was immediately obvious that there was a problem: I could get no slack in the cables at the carbs. In fact it was so bad that the new cables were pulling the butterfly assembly off the stop by a few mm.

Now I needed to decide where I'd made my mistake. I'd purchased the cables from my local BMW dealer who keeps my bike's serial number on file. I phoned the parts department and they confirmed that the cable part numbers were correct for my year and model. Next, I pulled one of the cables back out of the bike and compared it side-by-side with the old cable. There was a substantial difference in the "free length" and there's no question that was my problem. The length of the outer sheath, including the adjustment is important only in that it must be neither too long nor too short to make it from the handlebar control to the carburetor. This length must also take in to account changes associated with turning the bars lock-to-lock.

I also inspected the old cables very carefully - with a magnifying glass under good light. Yep! Something had been written on the carburetor end of the cable but age and wear had removed any possibility of reading it.

I posted a query on another list and immediately got responses from several very knowledgeable guys, Lloyd Provin Jr. and Tom Cutter. Also thanks must go out to Ray Brutti and Gary Sowter for helpful suggestions. The key question that the first two were asking was: what carbs do you have mounted? I did not realise that there were at least two major differences in these (GS) model BMW's. Turns out that my problem was directly related to this. My bike is a "Euro Spec", versus a "USA Spec". There may be many differences between the two, but for this missive the key difference is that the USA bikes were shipped with 32mm carbs and the Euro bikes got 40mm carbs. Tom C. also made the observation that there are a number of USA spec bikes that have been converted to 40mm carbs.

Tom C. sent along this URL: http://largiader.com/articles/cables/ - Here's another guy, Anton Largiader, who is definitely "paying it forward" and has done a tremendous amount of research to develop this list. The key items learned from Anton's article are:

-Free Length is the length of exposed cable when everything is pulled out of the sheath at the carb end. See the pictures on Anton's site.
-Overall Length (OAL) is the measurement from end to end INSIDE the ferrules. Same thing - great pics.

My problem is a lack of adequate "free length" as the cables supplied by BMW are for use with the 32mm carbs. These cables carry the part numbers - 32 73 1 454 584 and 32 73 1 454 585 and have a free length of 62mm. They are (from Anton's list) used on '86-on 32mm high bar bikes.

The cables that are needed for my Euro Spec bike are 32 73 1 458 090 and 32 73 1 458 091. These cables have a free length of 72mm. Anton's remarks are: '91-on 32mm GS/R - '86-on 40mm upgrade (not GS/R) probably will need this. The Euro spec bike is equivalent to the USA spec bike with carbs "upgraded" from 32mm to 40mm.

Mentioned here because it may become important to someone else is that 32 73 2 311 827 and 32 73 2 311 828 were mentioned by two of the contributors, Lloyd Provin Jr and Gary Souter. Gary remarked that his '94 GS/PD used these numbers. From Anton's list, those numbers show a free length of 84mm and the remark: " '91-on GS/R w/40mm carbs - extra length needed at both ends". Tom Cutter noted that these may do for my bike but to be careful as there may be too much free length for the adjustment that I have available. I have not been able to confirm this from the fiche that I have access to, but I'm willing to bet from the "extra length needed at both ends" remark that there is a difference in the handlebar assembly that requires the extra 12mm. My guess - not confirmed.

Other sources that have not been mentioned here are:
Robert "Snowbum" Fleischer (another big "pay it forward" guy) - see: http://bmwmotorcycletech.info/controlcables.htm
Also -
http://www.gunsmoke.com/motorcycling/r100gs/index.html
And -
Oak Okleshen, ABC Technical Consultant - not an online source

I hope this helps someone else down the road. I, for one, am going to do a lot more research in the future before buying anything.

Cheers,
March ABC#15235