Installing Symtec grip heaters on BMW K100RT++

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Objective
The objective of this project was to replace the existing BMW grip heaters with aftermarket heaters. I lost that functionality on one of my grips as a result of upgrading my front brake, including the master cylinder/throttle control. The replacement grips were not heated. I purchased the Symtec Complete Motorcycle Grip Heater Set and a pair of Pro Grip 713 rubber grips from Snow City Cycle. I needed the grips to be replaced because I would be destroying the BMW grips in the process. The symtec heaters have two printed circuit heating elements, with low and high temperatures. BMW achieves the same dual temperature control through the use of a resistance wire in the switch. There is a need to modify the standard BMW heater switch to accommodate the Symtecs and Smithduck describes that change in his instructions.
Parts
My existing heated grips had the following equipment, which was re-used in this installation:

• Heater switch on motorcycle dash
• Heater cabling in factory cable harness
• High rise BMW handlebars with cutouts for internal wiring

I purchased the following parts to complement the existing hardware:

• Symtec Motorcycle Heater Kit
• Pro Grip 713 Gel Grips

Smithduck, who is a contributor to many BMW forums, has posted instructions on the basic installation of a set of Symtec grip heaters on a K75/K100. These instructions are available at this location:

Smithduck's Instructions on Installing Symtec Heaters on a K100

I won't duplicate those basic instructions. However, Smithduck reccomends running the wires on the outside of the handlebars for convenience. This gets especially ugly when it comes to the throttle side grip.

I improved on Smithduck's the installation process by running the heater wires within the handlebars instead of outside as Smithduck describes. These are the steps I followed:

Clutch Side Heater
When it came to running the wires inside the handlebars, I needed a way to fish the wires through the inside of the bars. A string serves the purpose. I tied a string to the end of the existing clutch side heater wire and removed the existing clutch grip. The string was drawn through the bars using the same path as the original wires. I threaded the Symtec wire through the bar end weight and tied the string to it. I pulled the wire completely through the handlebars and out the hole near the tripple clamp. I formed the wires over the end of the bars so that the Symtec heating element was able to be wrapped around the bars. I secured the heater to the bars (self-adhesive backing) and pressed home the bar end. On a BMW, there is a large notch cut into the handlebar to accommodate the Symtec wire loop. Therefore, fitting the Pro Grip on was easy and straight forward because no wires would be pinched as a result of pressing home the Pro Grip rubber. Photo below shows final install:


Throttle Side Heater
The throttle side was harder. The constant twisting of the throttle puts a strain on the heating element wires and a solution was needed to allow the cable to thread through the bars yet remain loose and flexible against the rotational motion. The photo below shows that unless a modification was made, there would not be enough room for the wire to flex as needed. What was required was to open the end of the throttle shell to provide that room.

First I cut off the existing K1100 grip and discarded it. I began by wrapping painter's tape around the end of the plastic throttle shell and marking the point on the tape where the 7 o'clock cut-out in the bars was while the throttle was fully closed.

Next I rotated the throttle fully open and marked the other side at 3 o'clock.

I then drew a connection line about 5-6mm from the end. These formed by cut lines.

I took a hacksaw and carefully cut away the plastic on the shell. The last bits I used a utility knife to part the scrap from the shell.

I now had a cut-out that could accommodate the wire through a complete rotation cycle of the throttle.

I fished the wire through the bars and positioned the wires so that they nearly touched the handlebar ends at 3 o'clock while the throttle was at rest. This gave me maximum space to accommodate wire flex.


I tested the rotation and was glad to see that everything functioned as planned.

This is a YouTube video of the throttle being rotated

It is possible to see in the photo below that the space for the wire is larger and premature failure of the heater due to excessive wire flex-failure is not possible.

I then fitted the bar end and attached the grip.

The final assembly was to attach the grip heaters to the existing heater circuit. Since I was unable to find the BMW connectors, I used Amp connectors which were readily available from Sayal Electronics.

When everything was complete, I tested the heating. It worked great. I've very happy.