I was able to install my new grips today on my 2011 GTI LTD 155. I will show some additional photos below.
I also tried them on my 2001 GTX RFI. This ski has a thumb throttle and, while the grips fit fine, the throttle is way out of position for the thumb flange. So these new grips look like a no go for those looking to install these with a thumb throttle ski. More description and photos below.
1. Pop out the rubber cover with a flat bladed screwdriver
2. This will expose a 10mm bolt and a washer:
Undo that bolt with a standard 10mm socket:
3. Pull the grip straight off. Mine had a little adhesive, which @Coastijoe thinks may be used during assembly. I had to pull pretty hard, a couple of times, and it comes right off. You cannot twist these grips as there is an indexing boss cast inside the grip so that it only goes on one way and will align, or index to the correct angle. The slot in the handlebar is where the indexing boss inside the grip fits.
4. Slide the new grip directly onto the handlebar. Rotate slightly until the indexing boss aligns with the slot in the handlebar. As Coastiejoe said in his write up, just smack it home with your hand. Don't worry if it does not seat perfectly. When you reinstall the 10mm bolt and washer, it will seat the grip completely.
5. Pop your rubber protective cap back on and you are done:
Sitting on the ski, it is hard to describe how much more comfortable these grips are on your hands. Can't wait to ride. We won't be out til late April, so a couple of months, yet.
Both sides took me about 10 minutes total.
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Ok, now for the thumb throttle. This is on a 2001 GTX RFI.
The grip disassembly is exactly the same as earlier described. Mine had a plastic insert and not a washer. The grip installs fine.
BUT... Look at the angle of the flange compared to the location of the thumb throttle. No way!
-Dave