R80ST gets the GS Treatment

One more observation:

I already knew this to be the case, but definitely didn't realize the extent. The stock BMW speedo is optimistic. We all know that. What I didn't realize though is just HOW optimistic. Since hooking up the trailtech and having a working tach and speedo, I'm now turning 4180 RPM at 60mph whereas that engine speed had me over 70 mph previously. GPS agreed with my speedo REALLY well too. The stock wheel size setting on the trailtech had me within 1 mph of the GPS at 70mph. No wonder it always took me so long to go everywhere before. I was actually going 60 when I thought I was going 70.

RE: speedo error etc

I had always assumed...(!).... that a cable-driven speedo and tach would be accurate. BUT, I have learned through GPS that there can be substantial errors with cable-driven speedos, but still always assumed (!) that the tach was correct. Now I finding that I am shocked by how far off my /6 cable-driven tach is off when compared to a strobe tach....:eek1

The adjustments/calibration are all through the little magnetic drive, which makes it pretty tough for those of us who are ham-handed to fix.... does not respond well to the bigger-hammer-and-where's-the-blue-torch school of repairwork.... he he he....

Just saw this thread. What an amazing conversion this has been.
Absolutely clean even to those who have an eye for detail.

have ya'll been following the 'bogging down' thread with that guy in Mexico? He said at 5,000 rpms he's going 80mph. That seemed really off to me, think it has something to do with the cable error?

FWIW, my stock r80G/S turns 4800 rpms at 70 with a higher 5th. The HPN gear only made about 250 rpms worth of difference as per the Trail Tech.

Well, that's what my stock gauges said - 80mph at 5k rpm. I had an electronic tach that came standard on the ST and I believe (correct me if I'm wrong) that they're pretty accurate. The speedometer really exagerated my speed yet at the same time the odometer which is run off the same cable as the speedo was actually quite accurate, so the exagerated speed almost seems intentional on BMW's part.

Thanks, but the converSATION hasn't been very clean at all. The conversion looks cleaner in photos than real life (like anything). There is still plenty of wiring to clean up and little nitpicky stuff to fix, but at least it's rideable now. (as soon as I pull my second carb out of the death bath and put it back together)

By the way Chanderjeet, I'm a huge fan of your ride reports. Great photos and really cool looking trips. You've convinced me that I need to ride through India at some point. Keep those photos coming!

Haha, my bad... conversion ...
After watching your thread, i wanna make me a dual sport as well. It may not be a BMW but a royal enfield.
And im no craftsman like you sire but i will try my best.

Yes, that is correct: the odometer is geared through the cable, and unless you have a different circumference wheel mounted, is very accurate. That is the reason for the W=xx on the speedo face: to match it to the proper rear drive. The needle, however, can be mounted on the little magnetic drive in such a way as to be off... legend has it that BMW tried for maybe 5% optimism, for safety reasons as well as warm-and-fuzzies that the bike was so comfortable at those speeds...

Even more modern speedos are much the same. For example, my F650 speedo (cable driven off the front wheel) reads 10% high from 40 - 80ish. The odometer checked against my SS1000 mileage was within 1.3%

Based on the few Interstate jaunts on my ST where I had a good idea of the traffic speed around me, its speedo is very likely the same 10% optimistic.

(Now if I can just out to the garage and finish that transmission project on the ST - been down with a virus all week )

Speedos are usually optimistic. Odo's however, are usually pretty close to accurate, even though they share a PTO. I was led to believe this was for legal reasons.
Cant have a speedo read under your actual speed, that would lead to developing relationships with policeman friends.
And inaccurate Odo's lead to issues of mileage at resale, salvage, etc...

My speedo is about 10% off... way more noticeable the faster you go, as evidenced by GPS. Mileage is much closer. My girlfriends bike and mine are only off each other by 1 or 2%, 3 max. I noticed the same sort of thing when riding with a bunch of other guys when we all have roll charts. Everybody is off by a couple of tenths at the resets.

This might be of interest. I've tried to add an attachment but didn't see it in the preview post. Oh, well I'll try it anyway.

....here we go!!

Question 1: to those with non Bavarian vehicles sharing garage space:

Are your Guzzis, Hondas, Suzis, etc. also showing the "max. 10% permissible Tolerance"' ?



Question 2: Does anyone know how to fix this error on the cable driven speedo - is there any adjustments that can be done?


Cheers,

thjakits
'79 R100S

I had a GPS on my Kawasaki vn750 and my KLR, both displayed a faster speed than the GPS.

I have tried, been frustrated, but it CAN be done: remove the back of the units to get to the point where you can get at the magnetic disc. Very carefully make a precise index mark when the speedo is at zero, and then remove the needle. Move the disc away from the index slightly, remount the needle. Re-assemble, test ride. Then (probably!) do it again, and again, and again, until you have the desired speed range.

Probably best to let a real speedo shop do it, was my conclusion....

Here is an excellent primmer in getting into the speedo guts: he discusses fixing the odometer, but the process of "getting in there" is the same...

Odometer repair thread

Well, that looks like the definitive word. Nice find, horn.

Well, I hope it's helpful to some. Maybe it will settle some arguments. I don't know if that is still BMWs policy but I wouldn't be surprised. I had an '01 GS that indicated the speedo optimistically. No doubt it's the lawyer CYA syndrome that's implemented throughout the world.

This morning I changed ALL the fluids and found a couple of problems. First off my final drive oil was a little milky. Water's getting in there somehow and I don't like it. Second and more serious, when I dropped the tranny oil the magnet had the usual fuzz along with three small shards of metal seen below in the jaws of a 10mm wrench for scale. (sorry about the crappy cell phone photo) They are long skinny splinters and fairly thick. They aren't the flakes you usually see coming from bearing races. They have some thickness to them. I also took a pair of pliers to one and bent it. It didn't snap so it didn't come off of something really hard (like a bearing race).



To all of you who've been there before, what am I in for? Is this an indication of imminent tranny death, or could these just be a result of crunching into gear a few too many times? There are 15k miles on the box and it did sit for about 15-20 years. The tranny shifts fine and there's no feelable grinding when turning the wheel over on the centerstand. I realize nobody can tell me definitively one way or another, but I need some reassurance (or warning, but hopefully not). Anybody?

how much time before your trip?

Hi Airhead Wrangler, I just spotted this thread. I'm suprised I did'nt spot it earlier. Very cool bike project you got going there. I'm glad my skidplates could be part of such a worthwhile project. Keep up the good work. Let me know if I can help you out in the future. 2HE

Shoving off mid-september or october 1st at the latest, so plenty of time. I was just hoping that the tranny was going to be a grand that I didn't have to spend now. Damn it. The trip budget may have just gotten a little tighter. I'm going on a 800-1000 mile ride next weekend and after that I might drop my tranny oil again and look for any more evil. Problem is, what are the chances that those little shards even make their way to the magnet? For all I know, these little pieces could've been living in the bottom of the box for a while and only recently migrated close enough to the magnet to get picked up. Maybe I'll get one of those little magnets on a flexy wire, snake it in the drain hole and do some sweeping and see what I find.

Anyway, my feeling on the matter right now is just ride it and pay close attention to it - Feel for the first signs of any bad vibes, put it up on the center stand and turn the wheel often, change my tranny oil every time I change my engine oil and watch for any more chunks. After a few months of that I'll make my decision on whether or not to get it rebuilt. Anyway, what's the lead time to get a box built from any of the big names? (Anton, Oak, Ted Porter, etc.) They can turn them around in a few weeks right?

Do you know how to rebuild airhead transmissions?? Thanks, Ernie. Keep coming up with new goodies for our old bikes! American cottage industry at its finest.
Shameless plug for Ernie's wares: https://twinheadlighternie.smugmug.com/gallery/3463421_6XsAt#510440858_FFNER