K1100 Throttle Bodies On A K75

K1100 Throttle Bodies On A K75

I stumbled across this blog while searching for something else and, since I had some K75 and K1100 TBs on hand, I thought I'd give it a go. Despite the claim that the K1100 TBs are 3mm larger in diameter, I measured the butterfly discs when I had them apart and the difference in diameter is actually only about 1mm. This yields only a 6% increase in TB cross-section area but, since it's a "free" mod for me, I figured it was worth trying out on my K75 Frankenbrick. Every little bit helps, right?

Here's the two sets of TBs I started out with. One from a K1100 and one from a K75:

The K11 TBs have a vacuum hose across the back attached with Oetiker clamps. I cut those off with a Dremel cutting wheel and, since that hose is superfluous on a K75, I'll cap them off with some 1/4" (7mm) plastic caps from the hardware store.

Then I removed the #2 TB from the K11 TBs, slid the #1 TB back and cut off the excess at the ends of the mounting brackets at the front:

The shaft that drives the TPS on the K1100 is flat at the end while the shaft that drives the K75 TPS is longer and semi-circular. In order that swap those I took the nut/washer off of each of the rear butterfly shafts and then removed the butterfly discs. The little brass screws that hold the disk in the shaft are tough little buggers to break free so I had to use a good small screwdriver and lots of pressure to get them out, especially on the old K75 TBs.

And here's the final product with a 2V TPS installed:

Since my Frankenbrick already has a K1100 front end and throttle assembly with a K1100RS throttle cable, there shouldn't be any problems with the different throttle cable attachment. Although I may need to switch from a K1100RS cable to a longer K1100LT cable for routing purposes.

I probably won't get around to actually installing them on the K75 Frankenbrick for a while as I have other things on my plate but I'll come back and update this page when I do.