Rickman CR900 "GS" engine choice poll - big bore GS550-741/789cc vs GS750-894cc

[Chuck78]

No problem on the hijack, got me looking more & realizing from another member that a 730mm tall RF900R 43mm cartridge fork with dual 310mm discs would be an EXCELLENT alternate to me running a more budget oriented GS500E fork on my GS425-475cc project. $100 racetech emulators for the GS500 fork puts it up there in price, may as well just spend a little more coin & get full on cartridge forks that will dampen as good as emulators, stock! And come stock with adjustable rebound dampening in the latter years, and (?) adjustable preload. Nice. Just abandon the caliper mount on one side and run a single 310mm brake on this featherlight twin cylinder GS barebones racer. 43mm is a bit overkill on this light little bike though. I wonder if the rf600 or rf400 were available in the US?

 

[limeex2]

Not overkill if they work better. Maybe if they are heavier. I would take a little weight for a better fork. I believe they made a RF600 stateside. I pulled the triple's on the sprint. Back to back the triples are almost identical to a GS1000/1100. Bearings are the same so I threw the Sprint triple into a GS1000 bare frame. Fit perfect other than about a 3mm gap under the stem adjusting nut and the steering stops. I may have to call or pm you to understand what is involved in setting up the chassis other than switching parts. Thanks

 

[Chuck78]

As with a lot of newer bikes, the flagship model RF900R gets the awesome forks, and the RF600 & RF400 get damper rod forks that only look the same externally...

No cartridge forks & Yoshi cams this paycheck, wife's got expensive tastes, her January birthday just drained me... very excited about the RF900R fork prospect though. AND the custom CNC 1/2" Billet Al fork brace I pre-emptively got for gs500 forks that I didn't even own yet is the same style (oem steel plate w/ears on fork lowers ) as what the RF900R uses, makes this a total no-brainer!

 

[limeex2]

These are off of my Triumph Sprint. Handlebars are clip on style above the upper clamp. The triple trees went into a GS1000 chassis with no issues. I have an entire front end off of a spare Sprint. Where does one start for proper set-up? I will be using a Bandit rear end.

 

[Chuck78]

I think I'm going to start another thread solely about upgrades regarding revised frame and suspension geometry. rake and trail, ride height and suspension height changes front and rear, and overall effects on bike handling.

Limeex2, from what I've taken in so far on my quest for learning best modded setups, bolt the swingarm into the frame with the wheel in it. Jack the back end up by the frame, with no shocks until the swingarm is as close to a 12.5? angle to the ground as the chain line will allow without rubbing the swingarm pivot tube (gearing size - bigger front sprocket - allows closer to 12.5 degrees w/o chain rub on swingarm). You might only get to 9? or so with a vintage frame/engine.

Then with the front end and wheel installed, measure the rake angle of the head tube of the frame. Get the front tire diameter handy. Measure the offset of the triples precisely. Go to a rake& trail calculator online, or use the math formulas, and determine your trail.

You can also measure it manually with an L shaped framing square or plumb bob off the axle center, and a yardstick or straightedge and a very good eye and steady hand to simulate the steering stem centerline projected to the ground in front of the mark on the ground vertically under the axle. The amount the axle vertical centerline is from the line that the center of the steering stem points to is the amount the axle/tire contact patch "trails behind" the steering stem centerline.

Stock GS750 is around 4.65" trail (118mm?), quite a lot, very stable but slower turning than a sport bike. A stock 69-78 CB750 has about 5" of trail - cruiser territory, hence they steer like trucks even with a "fast for a cruiser" 28? rake. GS's are around 27?. Very stable, decent turn in but no sport bike. 4" is a safe trail # for more sport. stiffer than stock GS fork springs are needed to make sure you don't go into sketchy low rake/trail territory on front end brake dive, nasty head shake will ensue. Most modern sport bikes will be around 3.7"-3.9" trail ( which requires firmer aftermarket springs as you get closer to 3.7"), and 24.5-25.5? rake. Newer race oriented bikes are as steep of rake as 23.5. Going from 27? on a GS down to 26? or 25.5? shouldn't be too much trouble, but you need to make sure to watch the trail number. 3.7" may be a good idea to run a steering dampener for bumpy roads under braking & hard braking into corners (may upset the trail).

Bigger diameter front tire will make the trail # difficult to get down closer to 102mm/4", so a 19" will not work well here at all with a shorter fork than stock and modern triples that fit it. A 17" front wheel and a slightly shorter than GS length modern fork won't be much trouble at all to arrive at a good trail number. With 18" wheels, a 100/90 or 100/80 or 110/80-18 is helpful if you are running 35-45mm offset on the triples and trying to make the trail work.
More offset= less trail. Less offset = more trail. Modern triples have less offset generally, so you are likely to have too much trail with most 18" setups. With 17", should be closer. Taller tire or lessened rake (raise front/lower rear) will get your trail number higher if needed with the 17" front wheel.

Get all that figured out, then pick rear shock length. Easy if welding twin shock mounts to the Bandit swinger.a lot involved if monoshocking. Copy the linkage angles and positions of the donor bike if monoshocking, adjust shock position to get to the swingarm angle you settled at after getting the trail figured.

Trail is more important to get in the ballpark than rake, trail makes it stable/unstable and a good balance will be quicker to turn in than stock.

That's the result of my lunchtime reading the past few weeks...

 

[limeex2]

This is way over my head! Thank you for so much info. Once I start my mock up, this will get clearer.

 

[GregT]

This is way over my head! Thank you for so much info. Once I start my mock up, this will get clearer.

GS1000 with 17in wheels, 30mm longer shocks on GSX1100 swingarm, standard triple clamps and forks but more spring and preload measures up pretty close to your Triumph Sprint - though about 40mm longer in the wheelbase. 26deg rake, 96mm trail. Still pretty stable but turns very well indeed.

 

[Chuck78]

This is way over my head! Thank you for so much info. Once I start my mock up, this will get clearer.

Limeex2, sounds like you will be a lot better off buying a GS1100E swingarm than trying to monoshock or have twin shock mounts welded onto a Bandit monoshock swingarm. Lots of good shock options that will handle better than many "monoshock conversions" by amateur racers to cafes. Plus the gs1100e swingarm looks far better than the Bandit arm.
Look to YSS-USA.COM for awesome competitively priced shocks. For under $500 you can get very good quality piggyback shocks or adjustable rebound dampening "self adjusting emulsion shocks" - both alloy bodies. Good compliments to any cartridge front end conversion, assuming the triumph sprint is.

 

[Chuck78]

Doh! Hit a snag with the Rickman front end plans! Should've checked with Rickman owners a while back to learn that the Betor 38mm (dual disc) Rickman forks are a mere 715mm/28.149" tall axle center to top of stanchion!!! Offset on the triples is a whopping 60mm/2.362"!!!! So much for plans to use a standard vintage height (gs750/1000/kz1000) fork at 775mm!!!

I did find a flat track racer supplier that makes custom offset steering head bearings for +/-1? rake, and they also have custom Billet adjustable offset triples for 41mm forks in 7-5/8" spacing for $460 with 55-75mm offsets available.

I was having trouble finding triples with 50mm or so offset, but now looks like I may need to just go custom.

Now I'd probably resort to jacking up the rear 3/4", and dropping the front only about 1" lower than stock, and run these offset steering head bearings (sounds like an alignment nightmare or test in patience). I'd ideally like to get to 24.5-26.2? rake and 3.75-3.8" offset...

Not sure if I should slate the Superhawk forks for the daily rider GS750-920cc at this point for something shorter, as a 715mm Rickman fork vs a 775mm Superhawk fork even with 35-40mm eaten up by clipons - that's A LOT sticking out up top. I suppose it would enable me to run the clipons higher for more comfort!

I could travel limit the vtr1000f forks with topout spacers down to 4.1" travel from 4.7", and find clipons with the biggest clamping area possible, and that's put me at stock Rickman height... lose 1? with offset bearing adapters, take the rear end 3/4" higher and drop the front 1/4" more. There's 26? and may be able to run an ebay Honda oem triple.

The RF 900 43mm forks slated for the GS425 seem great for this at 730mm, run big clipons up top, but triple would likely mean even more searching and more likely to need a $550 custom billet triple, as a 43mm fork is going to be harder to find large offset cruiser bike and standard triples to use, as 41's seem more prevalent thus far in my searches with large offset triples and not being incredibly wide like the vn800 Vulcan or vf1100 magna triples...

May expand my search to shorter 41mm RSU forks after this discovery... more Hondas probably. Finding out heights of modern forks as well as triple clamp offsets are two very critical missing pieces of info on database lists of conversion info. All I find are steering stem bearing sizes, and fork tube diameters. The stem sizes are on the Allballs site slready. Lengths/spacings/offsets of modern fork swaps would clearly be far more useful info to compile... have to harass some ebay sellers for the info I suppose.

 

[Rensdw]

No problem on the hijack, got me looking more & realizing from another member that a 730mm tall RF900R 43mm cartridge fork with dual 310mm discs would be an EXCELLENT alternate to me running a more budget oriented GS500E fork on my GS425-475cc project. $100 racetech emulators for the GS500 fork puts it up there in price, may as well just spend a little more coin & get full on cartridge forks that will dampen as good as emulators, stock! And come stock with adjustable rebound dampening in the latter years, and (?) adjustable preload. Nice. Just abandon the caliper mount on one side and run a single 310mm brake on this featherlight twin cylinder GS barebones racer. 43mm is a bit overkill on this light little bike though. I wonder if the rf600 or rf400 were available in the US?

I have put a GSXR-750 (2001) front end on my 92 GS500E daily driver (well.....daily racer) and I had though about removing one disc because two would be overkill.
Guess what? I ended up ordering steel braided hoses to improve the braking even more! the reason is because I changed some of my riding styles, I now have two fingers on the lever at all times.
With two fingers on the brake it's a lot easier to brake before corners because there is no extra "things" I have to do like letting go off the throttle and reposition my fingers.
But if I have to brake real hard I have to squeeze so hard that it draws attention to it, thus I'm upgrading the hoses.

Still the two discs are probably overkill, but not when doing some serious downhill stuff in the alps or something, thank god for dual front brakes!

 

[tkent02]

I now have two fingers on the lever at all times.

Two fingers is one finger too many.

 

[Buffalo Bill]

Well, maybe you remember Yoshi extending the GS1000 superbike forks by welding on another 2" of pipe to the tops?
That would help narrow down your search.

 

[Rensdw]

Two fingers is one finger too many.

I know, but with one finger I cant squeeze hard enough, maybe when I have my steel braided lines installed, we'll see

 

[Guest]

Doh! Hit a snag with the Rickman front end plans! Should've checked with Rickman owners a while back to learn that the Betor 38mm (dual disc) Rickman forks are a mere 715mm/28.149" tall axle center to top of stanchion!!! Offset on the triples is a whopping 60mm/2.362"!!!! So much for plans to use a standard vintage height (gs750/1000/kz1000) fork at 775mm!!!

I did find a flat track racer supplier that makes custom offset steering head bearings for +/-1? rake, and they also have custom Billet adjustable offset triples for 41mm forks in 7-5/8" spacing for $460 with 55-75mm offsets available.

I was having trouble finding triples with 50mm or so offset, but now looks like I may need to just go custom.

Now I'd probably resort to jacking up the rear 3/4", and dropping the front only about 1" lower than stock, and run these offset steering head bearings (sounds like an alignment nightmare or test in patience). I'd ideally like to get to 24.5-26.2? rake and 3.75-3.8" offset...

Not sure if I should slate the Superhawk forks for the daily rider GS750-920cc at this point for something shorter, as a 715mm Rickman fork vs a 775mm Superhawk fork even with 35-40mm eaten up by clipons - that's A LOT sticking out up top. I suppose it would enable me to run the clipons higher for more comfort!

I could travel limit the vtr1000f forks with topout spacers down to 4.1" travel from 4.7", and find clipons with the biggest clamping area possible, and that's put me at stock Rickman height... lose 1? with offset bearing adapters, take the rear end 3/4" higher and drop the front 1/4" more. There's 26? and may be able to run an ebay Honda oem triple.

The RF 900 43mm forks slated for the GS425 seem great for this at 730mm, run big clipons up top, but triple would likely mean even more searching and more likely to need a $550 custom billet triple, as a 43mm fork is going to be harder to find large offset cruiser bike and standard triples to use, as 41's seem more prevalent thus far in my searches with large offset triples and not being incredibly wide like the vn800 Vulcan or vf1100 magna triples...

May expand my search to shorter 41mm RSU forks after this discovery... more Hondas probably. Finding out heights of modern forks as well as triple clamp offsets are two very critical missing pieces of info on database lists of conversion info. All I find are steering stem bearing sizes, and fork tube diameters. The stem sizes are on the Allballs site slready. Lengths/spacings/offsets of modern fork swaps would clearly be far more useful info to compile... have to harass some ebay sellers for the info I suppose.

Would the tripple trees from a gs1100gk (41mm tubes) be what you're looking for?

 

[Chuck78]

Would the tripple trees from a gs1100gk (41mm tubes) be what you're looking for?

Yeah but I've been looking for a pair of those for a long time, only finding complete forks or just lower triples. Honda PC800 triples are about the same width as the GK triples (so are SV650, but not enough offset), and if running these Superhawk VTR1000F cartridge forks, the 90's CB750 Nighthawk triples run 41mm forks on 18" wheels, bingo! Nighthawk and Superhawk run the same width (190mm fork centers), so they run the exact same axle, which I have now.

Now that I've discovered the Rickman forks were 715mm not 775-ish like the big 'Zuk's, I searched for other forks slightly shorter by 55-70mm that run either 296mm or 310mm rotors (so I can still run Honda rotors on GS wire spoke hubs). Finding fork extended length measurements is even more difficult than finding triple clamp width and offset specs, only luck is to search forums for riders who have measured various forks for swaps... there may very well be a Honda 41mm RSU cartridge fork in the 705-75mm range, but I happened upon another killer deal of $130 for some very clean RF900R Suzuki 43mm cartridge forks at approx. 730mm, and they run 310mm rotors and can run similar 6 piston calipers to the gsxr1000 01-02 's (early Hayabusa, same caliper different integral fork mounting), so it was an easy pick aside from triples.
So far I've found many newer Triumph's run 41&43mm triples in larger offsets, but now looking at a nicer aluminum top&bottom triple Yamaha VMAX 1200 93-05 triple. Looks to be mid 40mm's offset & 204mm-ish width. I think I can make this work on the Rickman, and I know I can make it work on the GS425-475cc where I can drop the front a lot due to the skinny 2cyl engine and only 2 pipes instead of a 4:1.
I may go with custom Billet triples from one of two flat track racer parts companies. Weiss will make a custom triple set for $325, best price. The place that makes custom offset bearings will make them for $400-something in 41mm max. A 3rd place will make them in 35mm or 43mm fixed offset or adjustabke. No pricing, their stuff looks trick, so $$$$$...

So I'm trying to decide wetter I want to spend $110 to get 1? offset steering stem bearings and have the hassle of getting them perfectly aligned so the fork isn't offset to one side or the other, or if I just want to settle for a larger offset $350 billet triple and 25.8 degreed rake 3.7" trail and the bike sloped .23" more downward to the front from my tire selection sizes and 2.4" combined total in longer shocks by 5/8"+ AND dropping the triples lower on the forks 35mm (1-3/8) for clipons on top. That's a total of 3" more slope to the front than stock Rickmans, not sure I'm comfortable with that for just under 26? rake.... maybe the custom triples AND the offset bearings will be in order...25.5? rake and 1/2" less drop in front end height is a good reason to spend hours nit picking offset steering bearing adapter alignment...

 

[Chuck78]

Also, back on topic, the need for shorter forks due to OEM Rickman length has me questioning ground clearance with a wide GS engine. I need to measure the Rickman frame from bottom of cradle's horizontal plane up to the bottom of the head tube on the frame. If the Rick runs the engine lower to the ground than a GS750, this is HUGE incentive for a corner carver to try out the 789cc GS550 option. Heck maybe even a Wiseco 844cc kit if I would lose too much lean angle with a gs750/1000 engine.
The polls are dead even now with 550 vs 750 base engines, but 2 say stock 750 pistons at 741cc, so the 894cc 750 is still on top with much GS1000 opinion...

 

[Guest]

I've got a '94 rf900 fork on my '83 750. But i'm swapping the legs out for a set from a 1200 Bandit to gain some ground clearance. I've run both tokico 6 pots and nissan 4 pots, the 4 pots are just a good.

 

[Chuck78]

I've got a '94 rf900 fork on my '83 750. But i'm swapping the legs out for a set from a 1200 Bandit to gain some ground clearance. I've run both tokico 6 pots and nissan 4 pots, the 4 pots are just a good.

The 6 pots run smaller pistons than the 4 pots, so the casting is not as tall on the outside in the piston area. The 4 pot nissin's on the Superhawk forks are a fraction of an inch from the wire spokes on my spoked wheels. Mags are more constant spoke thickness, whereas wire spokes are wider near the hub and taper in toward the rim. The wider casting area of the 6 pots is slightly further away from the hub than the 4 pots due to smaller pistons, so I have more clearance there, plus I'm gaining extra clearance going from 296mm to 310mm, as the wire spokes are narrower at this new caliper location 14mm higher/further from the hub.
If anything, the 4 pots are better. 6 pistons have a tendency to get gunked up more and not retract smoothly after 3500-6000 miles due to much more seal area & resulting seal friction. Worth the tradeoff for wire spoke clearance.

Are you looking to sell your RF900 legs? I may be interested in them if so, but not for a few paychecks. I just got a pair of low mileage legs and axle for $140, and there's a not as clean set on ebay for $109 shipped that I might jump on.

If you swap the B12 forks in, you're going to need different triples with more offset unless you run a 17" wheel with the rear shocks jacked up taller than stock. Your trail measurement will be longer than stock and it will steer pretty heavy.

 

[Guest]

The rear will be raised too, it has 17's front and rear. I plan on keeping the rf legs. This is it here.

 

[Chuck78]

kingofvenus, was the RF900 steering stem shorter than the GS? Longer? I am looking for options to swap into some VMAX1200 triples that are in the mail. I suspect the stem is much closer in height to what I need, but still a bit too long. nice double clamp bolt aluminum lower triple, so I can press out the stem and swap it.

The Rickman has an 86 Ninja triple in it now, but it is too tall, but the upper bearing slides up and down infinitely on it and the bearings have zero miles on them since their install 15+ years ago, so I considered possibly trying to have the top of it machined down identical to the VMAX, and pressing it in, or just pressing out the VMAX stem and having it cut shorter, as we know it fits the VMAX triple! Then I'd need new bearings again. at 52mm o.d., these steering bearings and Rickman head tube are MASSIVE... more welding area I suppose was the goal.