Retro Fitting Heated Grips to a 1990 K100RS

By Frank Sturzaker
sturzake@netcomuk.co.uk

I wanted to get some heated grips for my bike but wasn't prepared to pay out 180 ($280) for a new set. I bought some used grips from a breaker, fitted them and I am very happy with the result.

The new set would have included the grips fitted to a new set of handlebars. As far as I can tell, the new bars would have had the necessary holes in them with already routed wires together with the special bar end weights needed for grips. On the later model bars, a different arrangement exists with a different type of bar and end weight. This information below is for (I believe) the earlier type of bar.

The parts needed from a breaker are the two grips (plain left hand and throttle grip right hand), the 2 other pieces of wiring loom (the fascia switch plus the connection into the main loom) and two replacement bar end weights. I paid 50 ($80) for the component parts. Before you leave the breaker, do a simple continuity test on the heated grips (battery and bulb or voltmeter) to make sure they are in good order. Fitting them and finding one is not working is not good!

First, remove the existing grips. The end weights are removed by loosening the hexagon headed screws through the weights. They will pull off after this although they seem difficult - there are some O-rings which grip the inside of the bar. The Left hand grip is simple although it may be necessary to cut through a rubber or foam grip if it has been glued in place. The right hand (throttle) grip is more complex requiring the removal of the throttle cable from the grip. On the 16 valve K this is done by removing the single crosshead screw holding the throttle cable cover in place under the master cylinder. Then there are 2 other crosshead countersunk screws which fix the grip to the throttle plate. These are under the inboard end of the rubber grip and are difficult to see and hence to remove. They run from the grip pointing inboard into the throttle cable plate. Removing the cable should then leave the grip free to be slid off the bar.

Most work involved (time wise) is around routing the grip wires through the bars and out of a hole which needs to be made in the existing bars. I removed the fascia (switch) panel (2 hexagon headed screws), removed the 4 bolts through the bar clamps and simply rotated the bars enough to give access to make a 0.5 inch by 0.25 inch slot in the centre of the bars in the underside. It would be easier to remove all the switches, controls and master cylinder to allow the plain metal bars to be taken off and worked on a bench but this is not necessary. It is just a matter of making a hole (or two) and filing it to an approximate size. An assistant (such as a wife (in my case), girlfriend, offspring or partner) is a great help in holding the bars while this work is done. The larger the hole, the easier it is to thread the grip wires later.

Now to fitting the grips. The wires from the grips are thin and easily damaged especially where they go from the grip into the bar. The new end weights have a hollow core through which the wires (one brown, one black) must be threaded before threading through the bars. Each of the pairs of wires needs to be threaded down the handlebar to come out of the new hole made in the centre of the bars. I used a piece of cotton thread and a small metal nut (from a bolt) tied to the end of the cotton to thread the path in the first place from each grip. Letting the nut fall (or slide) under its own weight to the newly made hole in the bars (with a little shaking of the bars) is an easy way of making a way through the bars. Once the cotton was through, I pulled a thicker piece of nylon cord through (by tying it to the cotton) and eventually pulled the wires through by fixing them to the cord with insulating tape. If you have been given the female spade connectors attached to the grip wires, they may be a little difficult to thread but not impossible. If at first you don't succeed, have a coffee (or perhaps a beer) and try again. It does work eventually.

Once the first end of the wires from either (or both) grips is through, feed the remainder of the wires through. Don't just pull from the middle of the bars, push from the grip end whilst pulling from the centre. It will be obvious when you need to start to slide the grip on to the end of the bar. At this point be careful not to push the grip on to the bar too far - you will damage the wires as they come out of the grip on the end of the bar.

When the grips are on the bars far enough, it may be necessary to move the other switch units outwards on each bar to meet the inboard end of the grips. On my bike I had to move each one about one eighth of an inch outwards to ensure that the wires from the grips were not chaffing on the bar end especially the throttle which moves a lot. The switch units are held in place by a single clamping screw. The left hand grip is fixed on the bar by drilling a suitable size hole into the bar through one of two countersunk holes through the inboard end of the grip and inserting a countersunk self tapping screw into the bar. This can be tricky (bad experiences) if the hole is really a bit tight for the screws available. A tight self tap is not vital and be careful not to shear the head of the screw as it bites into the bar metal.

You should now have both grips fitted to the existing bars. Again, a simple continuity test at this point will save more re-work if you have damaged the wires or grips to this point. Route the grip wires forward and round the steering head. Replace the bars on the bike and clamp in place. Re-fit the throttle cable, insert the bar end weight caps and tighten them.

Fit the 3 position switch into the switch panel. Route the switch lead with the grip wires forward and down to the main left hand loom which disappears under the tank. At this point it is necessary to lift (but not remove) the tank. By lifting the rear of the tank from its locating positions on the frame and gently easing it backwards, it can be lifted away from the frame giving access (from a kneeling position) to the looms under the tank. An assistant is necessary to hold the tank away (resting most weight still on the right hand frame member) whilst you access the loom.

In the loom is a connector to match the one on the 3rd piece of the grip wiring. It is about half way along the loom under the tank. It is a T connection. Push the connectors together and then fit the grip wires into the 4 pin connector on the grip loom. This connector at first seems to have 5 wires going into 4 pins from the back. It is actually 2 black (earth) wires and one live (brown) which then feeds the fourth pin from the third pin. Use female spade connectors on the end of the grip wires to connect into this 4 pin connector - black to black, brown to brown.

The last connection should be the switch wire to the grip loom - this will only fit one way round.

Route the grip looms and other wires out of the way under the tank. Some small cable ties make a neat job of attaching the grip wires and loom to the main looms. Re-fit the tank. Re-fit the switch panel.

Test the grips by switching on the ignition and using the 3 position switch. My switch is off in the middle position with low heat when rocked towards the rider and high heat when rocked away. I am told that there may be other variation on this although I don't know.

 

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