ABS malf at speed - K-Bikes.com - Excellence in Motion
 
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post #1 of 10 (permalink) Old May 3rd, 2008, 2:22 pm Thread Starter
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ABS malf at speed

I am a recent owner of a used K12RS and after replacing a final drive that was left without lube by the shop that serviced it last it has been a fine bike. However I have noticed that pushing the speed up to about ninety the abs lights start flashing alternately. I don't understand the real cause unless the rear wheel is spinning ever so slightly faster than the front while under acceleration or the power necessary to maintain that speed. Anyone out there have a similar experience and better yet a solution??

1999 LT

2002 GS Adventure
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post #2 of 10 (permalink) Old May 3rd, 2008, 3:15 pm
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The variable reluctance sensors front and rear that pick up the ABS ring teeth, produce pulses. The faster the wheels rotate the lower is the output from these sensors (They are analogue not Hall effect), That's why the gaps measured at 3 points of wheel rotation are important. If they got bigger, then sensitivity goes down and pulses might get missed at higher speeds = ABS warning.

If your RD had no lube, I'd check the rear wheel shaft for any bearing play (check the front as well) If the wheels and ABS rings are moving due to bearing wear, the sensor gap will be changing.

How many miles do you think the bike did on the RD without lube?



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post #3 of 10 (permalink) Old May 3rd, 2008, 4:37 pm Thread Starter
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The bike had 12,500 when I bought it and had the service at 12. I put about 100 on it when I did a check and found the fd empty. The whole unit has been replaced, thank you beemer boneyard. It was installed by a reputable shop and they don't know what might be causing it unless there might be some air in the brake line. Everything works fine. I'll poke around some more and see if I can find anything. And the shop suggested going to a BMW shop and getting a readout from the puter. Which sounds like a reasonable step unless someone has a solution.

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post #4 of 10 (permalink) Old May 3rd, 2008, 5:11 pm
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More likely your problem is exactly what Vox said it is. The rear wheel ABS sensor gap is out of spec.

Pick up a manual, these things need it!
Attached Files
File Type: pdf '98-'00 K1200RS service manual ck-adj. rear wheel ABS sensor gap.pdf (371.3 KB, 18 views)

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST

Last edited by brucecha; May 3rd, 2008 at 6:48 pm.
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post #5 of 10 (permalink) Old May 3rd, 2008, 7:51 pm
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Quote:
Originally Posted by coldtrail
I am a recent owner of a used K12RS and after replacing a final drive that was left without lube by the shop that serviced it last it has been a fine bike. However I have noticed that pushing the speed up to about ninety the abs lights start flashing alternately. I don't understand the real cause unless the rear wheel is spinning ever so slightly faster than the front while under acceleration or the power necessary to maintain that speed. Anyone out there have a similar experience and better yet a solution??
..And the shop didnt pay for a new fd?....Maybe rear tire slip on the rim?...just a thought...maybe they used all their oil for mounting tires..thats why they didnt have any to put in your FD

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post #6 of 10 (permalink) Old May 3rd, 2008, 8:16 pm Thread Starter
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I was a little more than miffed when I found out there was no lube in the fd. And that it had only been 600 miles since the service. The shop's angle was that it had been almost a year since the service. My feelings were that since machines are inanimate and don't recognize time it was irrelevant that the service was that long ago. A couple of years maybe but the bike had been used lightly after the service then sold. Anyway a deal was cut with the mechanic who couldn't believe he would pull a boner like that and he would provide labor if I provided parts. I initially assumed that all that would be needed would be bearings and seals. Nope. The mechanic's first move was a preliminary disassemble that took about fifteen minutes and an analysis that the gears were shot. I agreed. You could see the mating surface deterioration. Therefore the cost of parts would be more than finding a good used one. So that's what we did. I escaped for a little over 400 and figured I was well off. Not lucky but what the heck. Do I think the shop should have paid for the whole thing. You damn right but I'm old and don't beat the crap out of people that piss me off like I used to so I went the route of least resistance. We parted friendly and who knows, it could pay off in the future.


And just a p.s. I don't have feeler gauges here at the house but visually it looks like the gap is a lot more than half a mm. I'll fiddle with it tomorrow and test it.

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2002 GS Adventure

Last edited by coldtrail; May 3rd, 2008 at 9:02 pm.
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post #7 of 10 (permalink) Old May 4th, 2008, 4:30 am
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Quote:
Originally Posted by coldtrail
And just a p.s. I don't have feeler gauges here at the house but visually it looks like the gap is a lot more than half a mm. I'll fiddle with it tomorrow and test it.
You can get quite a bit of adjustment of the gap by altering the position of the caliper on the mounting bolts.
Try this before resorting to removing the sensor and changing shims.

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post #8 of 10 (permalink) Old May 4th, 2008, 5:51 am
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Absolutely!

Many don't realise when they lift the caliper to help get a wheel out that the gap changes.

Also look carefully at the end of the sensor, if the gap has ever got to zero, with some bearing play, the end of the sensor will get ground away.

The other thing I didn't mention was the odo pickup sensor fitted in the RD (intermittent?). I'm pretty certain it's only used by the odo, but you never know with these complicated bikes.



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post #9 of 10 (permalink) Old May 5th, 2008, 1:24 am Thread Starter
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I checked the gap with feeler gauges and it is excessive. I tried repositioning the caliper and it started okay but when I finally tightened it down it went back to the original position. Is there some way of doing the bolts so the caliper stays where you want it? And thanks for the all the input.

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post #10 of 10 (permalink) Old May 5th, 2008, 10:55 am
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Quote:
Originally Posted by coldtrail
I checked the gap with feeler gauges and it is excessive. I tried repositioning the caliper and it started okay but when I finally tightened it down it went back to the original position. Is there some way of doing the bolts so the caliper stays where you want it? And thanks for the all the input.
Adjust the rear wheel sensor gap by using different thickness shims.
http://www.webparts.com/diagram.php?...66&hg=34&fg=15

Adjust as shown on page two of the pdf.
Attached Files
File Type: pdf '98-'00 K1200RS service manual ck-adj. rear wheel ABS sensor gap.pdf (371.3 KB, 7 views)

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST
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