Just went for a ride this evening on my new-to-me 91' k100rs and realized there was condensation
on the inside of the glass on the speedo and tach. Are'nt these supposed to be sealed and if it was broken is there a proper way to reseal it?
Thanks, Will

Yes it is supposed to be sealed but the reality is different.
This is a common problem when the outside temperature starts to be a bit cool and the heat from the engine warms up the instrument cluster.
On the latest K, BMW had tried to fix this problem by installing 2 Gortex vents on the bottom of the cluster.
Theoretically, the Gortex should let the air circulate but block the humidity entering the cluster. It doesn't really work!

Mine does the same thing...so I think you're pretty well stuck with the problem.

I think the heat doesn't come from the engine but from the instrument lights. A lot have changed them for LED's and have prevented a lot of fogging/condens on the inside with the lower heat from the LED's.

What can I say?

I think that you are right . I forgot that I read this somewhere else

Some of you may have a fit if you read this, but....I drilled 2 tiny (emphasize tiny) holes in the back cover at the lowest point near the center when the speedo is mounted. Do it with the cover off so you don't get shavings inside and don't accidently drill thru the circuit board. I don't get condensation anymore.

I also drilled holes on my K75 cluster, but did not see a great improvement.
I drilled them toward the top and at a 30 degrees angle (slanted toward the bottom). I was thinking that air circulation would prevent the fog.
Because I didn't find this solution working, I didn't do it on the K100.
Maybe the holes are to small (1mm diameter) and I would gain improvement by drilling them bigger.

Another solution that I am thinking is to place a little bag of silica gel (silicon dioxide-SiO2) inside the instrument cluster. Silica gel packets are found in anything that would be affected by excess moisture or condensation like pills container or packaging of electronic equipment.
Silica gel can adsorb about 40 percent of its weight in moisture and can take the relative humidity in a closed container down to about 40 percent. Once saturated, you can drive the moisture off and reuse silica gel by heating it above 300 degrees F (150 C).

Hi Guys,
If you read the stuff I put on the forum about changing to LED's it talks about sealing. So here we go, first off remove the cluster you will need a good set or Allen keys ball ended ones make it easier and remove the instrument cluster. Now Will's bike like mine will have the goretex membranes so take the screws out and separate the two halves of the cluster and thoroughly dry out the cluster say overnight in the air blast from a de-humidifier or on top of something warm like in the airing cupboard. Take the reinforcing pieces out the back of the case and seal them thoroughly so they cannot let moisture in there and use NEUTRAL CURE silicone if that is what you want to use do not use acid cure or you will destroy your instrument cluster. Treat all the plugs and sockets and connections with DeOxit, whilst you are in there fit LED's if you have them (well worthwhile by the way) and then replace the gasket with a new one and screw the two halves together and then tape over the whole joint between the two casings with 1" wide 3M black electricians tape . Due to the way the cluster mounts the tape is invisible. That should be the end of all condensation unless you have a crack in the housing I definitely would NOT drill any holes in the case.
Regards,
K-BIKE

I'm with you there. The fogging is a result of the humidity in the speedo (contained in the air when it was assembled or later opened) that condensates on the inside of the speedo glass when the temperature outside the speedo is higher than on the inside. Inside the contained air warms up (relatively) because of the lightbulbs fitted. As LED's produce far less heat when working, it reduces the temperature difference and thus the condensation. They tried to solve the problem by fitting goretex in the later speedos, but that was not completely successful. Be careful with applying heat, as I tried to dry out my unit in the oven at about 80/90 degrees C and ruined the gearindicator display in the proces. Them the brakes................