Rickman threadless vs GSXR threaded double locknut steering stems, CR900 project

If you've seen another post of mine, I picked up an abused wrecked and repaired/modded old abandoned Rickman CR900 project frame with a few Rickman parts on it still (most of the rearsets and rear brake, steel fuel cell missing the fiberglass tank cover, swingarm, axle, and some engine mounts. Since finding all original Rickman parts would run more than buying a complete Rickman CR, and take me many years to even come close, this frame already modded to fit GS1100E Suzuki engines, fit my checklist for ultimate vintage resto-mod racer type platform to build for riding in the Appalachian hills and mounts in Southeast Ohio and beyond (Eastern Kentucky - Red River Gorge especially, all of West Virginia's endless twisty roads especially the Northeast Monongahela Nat Forest mountains...)

The Rickman frames I have now discovered were built around 715mm long forks, which is incredibly short even in post-classic standards. the rake was already a lazy 28 degrees, so I can't just raise the whole bike up, it will kill my other mission of lower profile 110/80-18 front tire and longer rear shocks to steepen the rake and swingarm angles to more sporting standards.

The RF900R Suzuki forks are the same as the 775mm Bandit 1200 forks (one of the best RSU vintage looking upgrade candidates, best/most tunable dampening) except that they are 727mm tall. I could have more easily gone with some CBR600F4/F4i 755mm tall forks for what I am trying to do, but the brake mounts on the RF900 forks look much more vintage appropriate than the F4i forks, although the F4i forks will give me enough room to mount clipons on top of the triple, as I often go deep into the SE Ohio hills for 5-9 hour rides in some amazing twisties, and I wanted a little higher up riding position with this low front of frame Rickman design, especially with the long stretched solo seat gas tank. The F4i forks have the lower brake mount rearward much futher off the fork lower, which I don't care for too much, but are taller, run the very wide 80mm opposed piston brake cakipers further outboard for more wheel clearance to spokes, and have adjustable rebound dampening, whereas the better half of the RF forks came with rebound and preload adjustment, no compression (less critical anways).

I got a killer deal on some RF forks, and liked the appearance a slight bit better, but this creates some triple fitment issues I need to address here. See next post. (CBR900RR 6 bolt rotors with spacers and holes enlarged will bolt to my GS hubs, Hayabusa/Bandit brakes fit the RF900R forks)


Here's a mockup of the ride height (suspended frame by ratchet straps) with the swingarm angle topped out at almost 13 degrees (Dave Moss recommends no higher than 13.5 degrees topped out), shorter front tire and RF forks clamped at a height to simulate my front ride height and front tire radius. 25.6 degrees rake from 28 degrees is a pretty excellent result, using a 50mm offset triple will yeild 3.73" trail, 49mm offset will yeild 3.78" trail - a safer more stable bet in case my calculations have much margin of error. Front sprocket size likely needs increased 1+ tooth to give the chain better clearance to the swingarm pivot tube going with 50mm longer rear shocks.

So my issue is that I assumed I could lower whatever forks I used and run longer rear shocks to help increase the caster (steepen/decrease the rake) and then be able to clamp clipons on top of the triples, without hurting the cornering clearance much. Well the Rickman forks are pretty much spec'd at their shortest possible height, with the seal area lower than even modern 17" wheel bike RSU forks - hence @120mm travel, the lower triple really can;t be dropped any closer to the fork seals than stock Rickman ride height. I like the look of the RF forks, so Matt aka slikwilli420 is working with me to make some custom width and offset triples, and now looking to make them a step down offset as well so that I can still have a double pinch bolt upper stanchion clamp but have enough clearance to mount Vortex clipons or 35mm tall LSL 37mm risers on top of the triples.

I found that a 2000-ish GSXR600/750 or Hayabusa steering stem had nearly the perfect bearing surface spacings to work with a GS or Rickman frame, and am using that steering stem. The CBR600F4i forks in some VMAX 1200 43mm triples will just barely clear the brake calipers to the wire spokes by 1.5-2mm, and some angle milling on the inboard sides of the calipers would give some better insurance against wheel flex causing interference. This would work, but left me wanting to run custom wider 206mm triples for the slightly more vintage styled RF forks instead, although the brake mounts on the CBR600F4 forks will allow the same clearance in 198-200mm wide triples.

So to really get the height I need for 35mm tall clamp clipons up top, I realized that the only way to reasonably do that was consider machining the locknut thread areas off of the GSXR aluminum stem, and run a threadless stem setup with pinch bolt and top loading nut, as as the the original Rickman forks runs - you can see this in the Rickman parts catalog/assembly manual I have here with the GSXR stem:


This is the way all high end bicycles have converted to over the threaded locknut stem setup in the past 20 years, and I will tell you I PUNISH my BMX and mountain bikes with threadless stem setups like this, and they are far far more reliable in that application than the old threadless setups that I constantly was adusting in my youth as I abused and broke many BMX and dirt jumping frames/forks/bars/rims/etc.

The thing is, I don't recall ever seeing any other Japanese bikes or other vintage bikes that ran a threadless setup, although I was never looking for it until now. Honestly, on my first bearing upgrade to my GS750, I was shocked that a threaded single locknut setup with pinch clamp upper triple was all that held my GS front end together, I would have figured a threadless with top nut/bolt and pinch clamp triple would be superior.

So... Is this a terrible idea for me to convert this stem in this way? I have not read of Rickman owners complaining about it, but I was a bit uncertain about it since none of the Japanese bikes I've wrenched on had this setup. I will have a double pinch bolt triple on the stem and stanchions, and a GSXR alloy top nut for now, although may convert to internal fine thread M14x1.0 bolt on top to load the bearings.

Here at 1:15 in Rklystron's video, you can see first hand the Rickman threadless setup:
https://www.youtube.com/embed/H1FJndWJsa8

I had wondered how the steering stem was slammed right on top of the frame like that... This makes the 715mm Rickman fork height even more minimal. With a standard triple clamp vs the Rickman style, the fork length would need to be a in the 725+mm range.

Again, this is all being considered so that I can run clipons on top of the custom billet triples, as I wanted a more sporty riding position but not a race bike only position. I could just run regular handlebars, but clubmans honestly holding a set of clubman's in my hands seemed like I would be even further forward than clipons mounted under the triples! I'll have to run out to the garage and look at the wife's GS550 with clubman's, forgot she was running those late in the season.

I could also just run LSL 5 degree 37mm riser clipons under the triples to be up at the height of the triples and slightly higher than the original Rickman clipons, but honestly, I was considering running those LSL risers on top of the triples considering the very low front end design on the frame and possibly slamming the triple down right on top of the upper steering stem bearing.

^^^ very nice looking pieces that would be the most comfortable height clipons I would consider, but they are very spendy.. will delay my triple clamp custom purchase downpayment slightly...