K75s Speedometer down

[joetk75s]

I just purchased a K75s in absolutely wonderful condition. My first.

The speedometer is down. It registers only 25% of the actual speed I am going. Is this a common problem? Is it fixable by an amature, or do I need to send it out for repair? The rest of the console (tach, other lights and indicators) all work fine.

Thanks in advance.

Joe

[kbasa]

Take a cruise over to www.ibmwr.org and visit their Kbike tech pages. You'll see all kinds of solutions for Kbike speedos.

I've used them myself to fix a somewhat recalcitrant Kbike speedo....

[JIMVONBADEN]

Originally posted by Joe_t
I just purchased a K75s in absolutely wonderful condition. My first.

The speedometer is down. It registers only 25% of the actual speed I am going. Is this a common problem? Is it fixable by an amature, or do I need to send it out for repair? The rest of the console (tach, other lights and indicators) all work fine.

Thanks in advance.

Joe

Very common.

If you find, after checking out the IBMWR K-Bike Tech Articles that you need to replace it, look on e-bay. They have a couple a week on there for around $100.

Jim

[montana]

Or substitute a Sigma Sport cycle computer for about $20. That's been done often - search this forum for at least one topic on the project. Or go full GPS.

[JIMVONBADEN]

Originally posted by Montana
Or substitute a Sigma Sport cycle computer for about $20. That's been done often - search this forum for at least one topic on the project. Or go full GPS.

True, it would work, and be effective. But it would look odd, and wouldn't do much for resale value. A GPS is a good idea, but pretty expensive for a decent one!

Jim

[90288]

Your message couldn't be more timely.

As I type this my 85 K100RT speedo is on the workbench.

ÔÇó Fogging problems
ÔÇó No speedo
ÔÇó Both fuel lights on all the time
ÔÇó Tail light bulb indicator on all the time

I got caught in the rain a few weeks back and that's when all this started. The gasket which seals the unit is shot and allowed moisture inside.

When I cracked it open, there was VERY noticeable amounts of water inside.

I have a gasket on order and I'm going to give the connections a good dose of contact cleaner as well.

When I'm done, I'll take some electrical tape wrap it around the two halves giving it an extra layer of protection.

I had a K75S with the same problem.

For as nice as BMW's are, the team who designed the speedo really blew it.

[JIMVONBADEN]

Originally posted by gsmetal
Your message couldn't be more timely.

As I type this my 85 K100RT speedo is on the workbench.

ÔÇó Fogging problems
ÔÇó No speedo
ÔÇó Both fuel lights on all the time
ÔÇó Tail light bulb indicator on all the time

I got caught in the rain a few weeks back and that's when all this started. The gasket which seals the unit is shot and allowed moisture inside.

When I cracked it open, there was VERY noticeable amounts of water inside.

I have a gasket on order and I'm going to give the connections a good dose of contact cleaner as well.

When I'm done, I'll take some electrical tape wrap it around the two halves giving it an extra layer of protection.

I had a K75S with the same problem.

For as nice as BMW's are, the team who designed the speedo really blew it.

A couple pieces of advice based on years of electronic experience:

*Contact cleaner is a good start. But use a hair dryer on low heat to make sure all the water is out. Moisture can hide for weeks, even when it appears dry.

*Use a pencil eraser, wiped frequently on an abrasive cloth like denim, to clean all of your contacts. It's very effective at reducing corrosion on copper and solder contacts.

*Dont use electrical tape to seal your edges. It doesn't work very well for sealing out moisture, and it WILL eventually fall, or slide, off and leave a nasty and sticky residue on your speedo. You might want to use a thin bead of black silicon sealant around the case.

*Dont forget replace the rubber grommets on the back where the wiring enters.

Hope this helps,

Jim

[deilenberger]

Originally posted by JimVonBaden
A couple pieces of advice based on years of electronic experience:

*Contact cleaner is a good start. But use a hair dryer on low heat to make sure all the water is out. Moisture can hide for weeks, even when it appears dry.

*Use a pencil eraser, wiped frequently on an abrasive cloth like denim, to clean all of your contacts. It's very effective at reducing corrosion on copper and solder contacts.

Using a pencil eraser would be difficult to do on a K bike instrument pod - the contacts are square pins going into square receivers. The usual way to enhance the conductivity of these is twofold:

1. Give a very slight twist to the square pin - it exposes new sharp edges to the square receiver.

2. Use a bit of antiseize that contains metal (look for the silver colored stuff) - it helps seal out air and moisture while not reducing conductivity (which di-electric grease WILL do).

I'd also suggest adding 1/8" foam on the back of the two plastic arms that hold the contacts going to the speedo and tach (they'll be obvious when you open it) - so the case presses these arms into better contact with the boards below them. BMW did this modification on later model K pods.

*Dont use electrical tape to seal your edges. It doesn't work very well for sealing out moisture, and it WILL eventually fall, or slide, off and leave a nasty and sticky residue on your speedo. You might want to use a thin bead of black silicon sealant around the case.

Dunno where you get your electrical tape - but I used it for 6 years on my '85 K100RT and have it on THE K75S - for about 2 years now. It has not failed, slid or come off. Scotch Brand is about the best quality.

On most of the K bikes - the area that the tape is put in (over the large sponge rubber O ring sealing the case halves together) isn't visible with the pod mounted to the bike.

Black silicone (silicon is a crystal used in semiconductors) might be a very BAD thing to use for this application unless you use a specific ELECTRONIC GRADE.

The normal stuff gives off acidic fumes - that smell like vinegar - that WILL attack the contacts inside the case and may attack the circuit traces on the flexible circuit boards inside the case. Not a good idea at all.

*Dont forget replace the rubber grommets on the back where the wiring enters.

Ummm.... what rubber grommets?

The K instrument pod has square pins that protrude through holes in the case. Not a grommet to be seen. There is a rubber seal of sorts on the cover that goes over the connectors - but I've never seen this fail, and it's effect on waterproofing the pod is questionable at best.

Hope this helps,

Jim

Again - I'd suggest looking at the K-tech-FAQ's on http://www.ibmwr.org - lots of experience there with K instrument pods and lots of good advice.

[JIMVONBADEN]

Originally posted by deilenberger
Using a pencil eraser would be difficult to do on a K bike instrument pod - the contacts are square pins going into square receivers. The usual way to enhance the conductivity of these is twofold:

1. Give a very slight twist to the square pin - it exposes new sharp edges to the square receiver.

2. Use a bit of antiseize that contains metal (look for the silver colored stuff) - it helps seal out air and moisture while not reducing conductivity (which di-electric grease WILL do).

I'd also suggest adding 1/8" foam on the back of the two plastic arms that hold the contacts going to the speedo and tach (they'll be obvious when you open it) - so the case presses these arms into better contact with the boards below them. BMW did this modification on later model K pods.


Dunno where you get your electrical tape - but I used it for 6 years on my '85 K100RT and have it on THE K75S - for about 2 years now. It has not failed, slid or come off. Scotch Brand is about the best quality.

On most of the K bikes - the area that the tape is put in (over the large sponge rubber O ring sealing the case halves together) isn't visible with the pod mounted to the bike.

Black silicone (silicon is a crystal used in semiconductors) might be a very BAD thing to use for this application unless you use a specific ELECTRONIC GRADE.

The normal stuff gives off acidic fumes - that smell like vinegar - that WILL attack the contacts inside the case and may attack the circuit traces on the flexible circuit boards inside the case. Not a good idea at all.


Ummm.... what rubber grommets?

The K instrument pod has square pins that protrude through holes in the case. Not a grommet to be seen. There is a rubber seal of sorts on the cover that goes over the connectors - but I've never seen this fail, and it's effect on waterproofing the pod is questionable at best.



Again - I'd suggest looking at the K-tech-FAQ's on http://www.ibmwr.org - lots of experience there with K instrument pods and lots of good advice.

Guess I was put in my place. 8 years military experience in electronics 15 years ago obviously doesn't apply today.

The gromets that the wires pass through on my bike are there, and I'll stand by the electrical tape comments. I've had it slide and leave a gooey (sp) mess on many items. Just maybe not where you used it. I must have misunderstood the aplication.

I've never heard of pure silicon interfering with circuits. We used it all the time on aircraft.

Don knows K bikes better than anyone, so go with his advice.

Jim

[deilenberger]

Originally posted by JimVonBaden
Guess I was put in my place. 8 years military experience in electronics 15 years ago obviously doesn't apply today.

The gromets that the wires pass through on my bike are there, and I'll stand by the electrical tape comments. I've had it slide and leave a gooey (sp) mess on many items. Just maybe not where you used it. I must have misunderstood the aplication.

Jim,

Where exactly are the gromets? There may be some around the base of the wiring connection cover (which screws into the rear of the pod) - but there sure aren't any around the actual connectors.

I've never heard of pure silicon interfering with circuits. We used it all the time on aircraft.

Bet it was some very expensive military grade electronic grade silcone sealant (Jim - silicon is a hard crystaline material that semiconductors are grown on.. silicone is the stuff used in plastic boobs, and for sealants of various types.. BIG difference for both applications.)

Don knows K bikes better than anyone, so go with his advice.
Jim

Dunno about better than anyone - my knowledge is really restricted to the ones I've owned and what I can project to models I haven't owned that use the same systems. I have taken K instrument pods apart WAY too many times (both for repair and to install Fuel+'s in them).. so I'm pretty familiar with them.



Best,

[JIMVONBADEN]

Originally posted by deilenberger


Jim,

Where exactly are the gromets? There may be some around the base of the wiring connection cover (which screws into the rear of the pod) - but there sure aren't any around the actual connectors.

I wasn't referring to the gromets on the connections, just the ones sealing the wires as they enter the speedo case.

Bet it was some very expensive military grade electronic grade silcone sealant (Jim - silicon is a hard crystaline material that semiconductors are grown on.. silicone is the stuff used in plastic boobs, and for sealants of various types.. BIG difference for both applications.)

Sorry, my spelling sucks, silicon(e) sealant. Similar to what we used on cars. Looked and smelled the same. Could have been different, but I still haven't heard of the fumes disturbing electronic components and connections. As a matter of fact I have used it on all maner of low and high temperature electronic applications, and the silicone I purchased came from Pep Boys. Still, I could be wrong.

Dunno about better than anyone - my knowledge is really restricted to the ones I've owned and what I can project to models I haven't owned that use the same systems. I have taken K instrument pods apart WAY too many times (both for repair and to install Fuel+'s in them).. so I'm pretty familiar with them.



Best,

From what I have seen, you are the most knowledgable on the K bikes. Also not unwilling to share.

Jim

[LORAZEPAM]

I have used Dow Corning silicone to tamper proof hundreds of electronic circuit boards, and never had a problem with it. I have found it to be an excellent sealant in many different harsh conditions. Just thought you should know this Don, and if you would like to try it I have not experienced any corrosion from its use.

[deilenberger]

Originally posted by lorazepam
I have used Dow Corning silicone to tamper proof hundreds of electronic circuit boards, and never had a problem with it. I have found it to be an excellent sealant in many different harsh conditions. Just thought you should know this Don, and if you would like to try it I have not experienced any corrosion from its use.

Dow is the maker of one of the electronic grade silicone sealants.

Does the stuff you use give off a vinegar smell as it cures?

If so - that's acidic acid fumes - not good around electronic components. The fact that you've done hundreds of circuit boards without a problem means you're using the right stuff, or are very lucky.

BTW - there is a REASON that electronic grade silicone sealant is made.. and the reason is corrosion caused by the acidic acid fumes.

Here is a link to the stuff I'm typing about:
http://www.mgchemicals.com/products/...rical_app.html

And to quote from the specifications for one of the products discussed:

"RTV162 White, one part, high strength, low odor, non-corrosive neutral cure, electronic grade silicone adhesive sealant. Meets Mil spec requirements and UL recognition. "

Note the "non-corrosive neutral cure"

Here's another link: http://www.intek-uk.com/electronic.htm

To quote them: "Non acid curing grades offer little or no risk of corrosion to components, copper, bare wires, coils etc. "

And from General Electric: http://www.gesilicones.com/silicones...hiba/business/ portfolio/1prtv/alkoxy/default.shtml

Quote: "A non-corrosive curing process that does not produce exothermic heat or corrosive by-products; can be used on corrosion-sensitive electrical and electronic equipment with no adverse effects."

There - I think I've beaten the subject to death

The real point is - why bother using silicone sealant in this application?

The good quality electrical tape will seal it up just fine, is easy to remove, hasn't degraded on the bikes I've used it on, and presents no risk to the components inside the instrument pod.

Best,

[dlearl476]

Three words:
HOT GLUE and CAIG

[LORAZEPAM]

Guess I was lucky, Don. I now have been truly enlightened in the field of silicone sealants. The stuff we used would knock a crack head off a glue wagon. It smelled nasty. Thanks for the info, I will use it in the future.