K100RS4Vs, K1s and 92/93 K1100s have an ignition amp that attaches to the front left of the battery tray. When the heat sink compound between the ignition amp and the battery tray deteriorates over time the ignition amp gets too hot and causes the bike to run poorly when things warm up.

Preventative maintenance: Go to a local electronics store and buy a small tube of heat sink compound. Take the ignition amp off of the front of the battery tray and thoroughly clean off all of the old heat sink compound. (Use steel wool or a wire brush.) Put a nice healthy dose of fresh heat sink compound on the back of the ignition amp and reassemble. 

This has been known to cause the above mentioned K models to run very poorly once they warm up and, if you don't know about this, you could waste LOTS of time and money trying to figure out why in the heck your K is running like crap.

This is inexpensive and very easy preventative maintenance. I'd guess 50K miles or every few years is a good maintenance interval for this. If you're doing a spline lube then you have to pull the battery tray off anyhow so that's also a good time to do this.



This does not apply to 94+ K1100s as the ignition system on those bikes does not utilize an ignition amp.

First time I did mine the heat sink compound was a crumbling mess, one really hot day and it would have frittered.

Thank you Duck that's awesome advice. Pity I have just put her all back together but at least if I have an issue I know where I'll be going first!

Metholated spirits will shift the old heatsink crap too. It's what I use for cleaning CPUs in PCs. A citrus-based screen cleaner works too, surprisingly enough.

duck wrote:K100RS4Vs, K1s and 92/93 K1100s have an ignition amp that attaches to the front left of the battery tray. When the heat sink compound between the ignition amp and the battery tray deteriorates over time the ignition amp gets too hot and causes the bike to run poorly when things warm up.

Excuse me for my poor (continental European) command of these terms - "ignition amp" ??? Amplifier? Can someone post an image of this part?

I have a K 1100 RS that was produced in 03/1993, so I guess my bike has this too

RicK G wrote:First time I did mine the heat sink compound was a crumbling mess, one really hot day and it would have frittered.

That's so true Rick. I came across the exact same thing when I had to move the amplifier on my first version Flying Brick.

ffbikersa wrote:

duck wrote:K100RS4Vs, K1s and 92/93 K1100s have an ignition amp that attaches to the front left of the battery tray. When the heat sink compound between the ignition amp and the battery tray deteriorates over time the ignition amp gets too hot and causes the bike to run poorly when things warm up.

Excuse me for my poor (continental European) command of these terms - "ignition amp" ??? Amplifier? Can someone post an image of this part?

I have a K 1100 RS that was produced in 03/1993, so I guess my bike has this too

Don't have a picture, but you cannot miss it, it is attached to the front left side of the battery tray.

ffbikersa wrote:


Excuse me for my poor (continental European) command of these terms - "ignition amp" ??? Amplifier? Can someone post an image of this part?

I have a K 1100 RS that was produced in 03/1993, so I guess my bike has this too

I posted this picture when I started this thread. Don't know what happened to it.

It bolts to the front of the battery cradle Tarik also make sure the small earth wire from the battery cradle to the engine is good.

Could this be my problem? After sorting the temperature sensor yesterday, I took the bike for a short run around the block to find some grass to test the ABS was all tickity boo. It is. However the engine will not idle when hot and constantly stalls when revs are low, like coming to a standstill. Pull the clutch and she stalls. Bike will start again no problem and is not running rough at all. Just won't idle. I had the panel that the ignition amp is attached to powder coated (along with a heap of other stuff) and have not refitted the ignition amp with any heat sink compound. The amp came away from the panel easily enough when I removed it and I simply bolted it back on later. Could this be a possible cause of lack of idle when hot? I do not believe the problem was there before I started the rebuild although I cannot confirm this.

Quite possible and remove the powder coating where the amp sits as it will not transfer the heat very well then reseat using the heat sink compound

And make sure the plug is fully seated. Don't ask me how I know.

Thank you for the replies and the heads up on removing the powder coat. Yes, I too have fallen foul of the odd 'don't ask me how I know' trick a few times over the years, as I guess we all do when we tinker with our machines.

RicK G wrote:Quite possible and remove the powder coating where the amp sits as it will not transfer the heat very well then reseat using the heat sink compound

I wonder how much having the rest of it powder coated will impact the battery tray's capacity to dissipate heat.

It's all apart and now I remember... The aluminium heat sink was not removed and was taped off when sent to be powder coated. Looking at the aluminium plate and how it is fastened to the steel I decided that it is not designed to come off easily. I am guessing that this is the heat sink rather than the steel frame. Is this correct? Aluminium is a much better heat conductor that steel and being a solid 4mm thick plate makes sense as it will conduct more heat. However when I refitted the amp it was simply bolted up to the heat sink and knowing what I know now (thanks Duck) clearly some compound was called for. The remnants of the old compound was a crumbly mess that scraped off very easily. 
I will report back when reassembled and test ridden.

Yep certainly made a difference and combined with a good fast road test she is now idling beautifully! When I pulled it apart to apply the heat sink compound I discovered that both mating surfaces were convex, so sweet FA of the surfaces were actually touching each other!