There are several ways to mount a 1" RAM ball into a steering stem, and I've probably tried most of them! The most obvious, perhaps, is to use RAM's own offset mount:
[image: RAM-B-342.jpg]
Unfortunately, in RAM's infinite wisdom, they have manufactured the rubber/plastic insert in such a way that it is both too big (the cylindrical top part) and too small (the tapered part) to fit snugly into a VFR's steering stem hole, which measures 19mm (3/4"), so it is fairly useless as delivered. I'm sure I could eventually find an appropriate 19mm OD hard rubber cylinder with a 6mm hole through the middle, but where's the fun in that?
So I decided to try something else. The big problem with a steering stem mount, btw, is keeping the ball from rotating once you've attached something like a heavy GPS unit onto a big lever (which is what a RAM arm essentially is) fitted to the ball. Things I've stuck into the stem hole in the past have tended to un-screw at inopportune moments, but my solution is admittedly another variation on that same theme: I bought a Pro-Bolt Aluminium Top Yoke Nut, which replaces the top steering stem nut on most Hondas (M24x1.0 thread), including my VFR750FP, VFR800FiY, RVF400RT, CBR250RRR and CBR400RRN:
[image: PRO%20BOLT%20ALLOY%20HONDA%20TOP%20YOKE%]
This same nut does not fit my VFR400RN NC30 (more about that later, perhaps), but does fit a huge number of modern Hondas. It's not cheap (£13/$18), but it helpfully already includes a nicely centred 7mm hole. The same nut (but without the hole) is also avilable in titanium from Pro-Bolt and TitanClassics, but I'm happy to use aluminum.
The OEM chrome top nut takes the same 30mm socket as the Pro-Bolt alloy one, so swapping the two is a doddle. Although the correct drill size to tap an M8x1.25 threaded hole is 6.8mm, the 7mm hole should be sufficient. (I used a centering tap holder from McMaster-Carr, I believe it was--helps keep the tap perpendicular to the surface of the work.)
[image: 20150315_152832x.jpg]
I decided to use an A2 stainless steel socket cap screw and tightened it into the now-threaded M8 hole in the top yoke nut:
[image: 20150315_153146x.jpg]
Which got topped with an M8 stainless steel lock washer and looks like this:
[image: 20150315_153230x.jpg]
The RAM ball I'm using is a pn. RAM-B-273-M6 (about $8):
[image: RAM-B-273-M6U.jpg]
Ram does make a 1" ball base that can be used with an M8 socket cap screw (pn. RAM-B-367, about $13):
[image: RAM-B-367U.jpg]
But, it doesn't have any kind of flange on it, so I decided to drill out the thread on the M6 version (which I've done in the past--there's plenty of metal) using a 6.8mm drill bit and my drill press. (Individual metric drill bits in the appropriate metric tapping hole sizes are available at McMaster-Carr):
[image: 20150315_153311x.jpg]
After a bit of "one-grunt" torquing, I had this:
[image: 20150315_160830x.jpg]
Which, 105 Nm later, looked like this:
[image: 20150315_152637x.jpg]
And, with a RAM arm attached, like this:
[image: 20150315_183434x.jpg]
The RAM ball is fairly solidly mounted to the top nut, so I hope it stays put! If it doesn't, I suppose I could try using Loctite, or even fitting a tiny rolled pin or two? However, I am sure that the top nut itself will not loosen (105 Nm!)...
I want to fit one of these to each of my bikes (except for the RC46, as it has a tank-bolt mount already), so keeping the cost down was a consideration, and my total investment turned out to be about $25-28 each. As mentioned above, the NC30 has a different steering stem size, which I think is the same as the RC30 and a bunch of Kawasakis, but is unlike any other Honda, so neither Pro-Bolt nor anyone else seems to make a similar domed nut to fit that bike (I think the thread is M32x1.0). So if I want to do the same for that bike I will be looking at very expensive custom machining, unfortunately.
As I had enough parts, I made two of these today and will probably make some more soon. Now all I need is to test them... :wink:
Ciao,