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Discussion Starter #1 (Edited)
I was fairly set to use some Suzuki RF900R 1997 43mm cartridge forks on my Rickman CR900 project, but I am fairly certain that if we do decide to road race this bike, the forks will bump it out of the class of similar bikes that it will be competitive against. It's a shame as they look very much like many vintage forks and have superior damping to most other options of this height.

My attention was turned to 1989 GSXR1100K cartridge forks. I recall hearing that the only people that run these forks as an upgrade are generally running them to fit within vintage racing regulations, as the gsxr1100k model was considered to have suspension issues (banned from the Isle of Man after 2 fatal crashes), & the forks really must be sent to Racetech to have them custom assemble cartridges for these forks.

I'm still not certain we will race this bike, as the 489cc GS425 Suzuki project seems more appealing to myself and my 3 buddies with vintage racing interest, but if I am starting with a clean plate, I figured I might as well just go for what makes the most sense if we were to race it.

So on a 1977 Rickman CR900 that is either 920cc or 1085cc, would these 1989 gixxer forks still allow it to remain in the same class as a bike with basically all 70's race parts? What about floating rotors?

I am in Ohio. I have not looked into what vintage racing sanctioning bodies are active around this part of the country, but I believe WERA may be. I know AHRMA has not done AMA Vintage Motorcycle Days for quite a long time.

Thanks,

Chuck in Ohio
 

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It's nothing to me because I don't even live in the same country as you and please don't take this as a slight, but what class do you hope to compete in and are the vintage racing rules really that ambiguous down there?

WERA Rules link -> Chapter 11 ... "Suspension: Forks: All machines must use period type forks." <- This statement seems to be fairly universal to any vintage racing I've ever been involved in ;) & if you just whooped me in a vintage race and my bike was all period, I would certainly be protesting your choice of equipment.
I don't have a horse in this race so :eek: I'll shut up now, but am very interested to hear the outcome.
 

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Discussion Starter #3
I'm not sure on what class a Rickman would fit into, as it was available in very limited numbers as a complete bike built at a factory which employed up to 130 workers, but more readily available as an aftermarket upgrade chassis kit minus engine exhaust and wiring...
 

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Discussion Starter #4 (Edited)
WERA Rules link -> Chapter 11 ... "Suspension: Forks: All machines must use period type forks." <- This statement seems to be fairly universal to any vintage racing I've ever been involved in ;)

From your link:
VINTAGE CLASSES
WERA Vintage has three classifications of racing machines: “GP”, “Formula”, and “Vintage” - V1 through V 7. Many machines will fit into more than one classification, either as the primary class or as the bump-up class.

“GP" - These classes are for older factory “purpose built” racers and street machines which may be built up with any “of the period” GP, engine, transmission and frame modifications.

“Formula” — Are Vintage classes which allow machines comprised of mixed origin or composition which were in use prior to the class cut-off date.

“Vintage” - The Vintage classes are based on “production" street machines. “GP” and “Formula” classes are allowed to “bump up” into certain Vintage 1 thru 7 classes. Factory “purpose built” machines must enter the next higher displacement Vintage class, i.e;, 500GP into V3 (750cc) class, H-D XRTT 750 must enter V4 (1,000cc) class, etc.
Performance indexing of machines from a different era or displacement category may happen to help grow grids and add to the competition level of a class. Any machine in the eligible machines listing with “(SS Spec)” after it must conform to the Superstock Specifications as listed in Chapter 9.
 

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Discussion Starter #5 (Edited)
Vintage 5
Pre 1983 2-stroke factory road racers up to 500cc.
Pre 1983 Production based 2-stroke up to 750cc.
Pre 1983 4-stroke push rod unlimited displacement.
Pre 1983 OHC Twins to 1200cc.
Pre 1983 OHC 2 valves per cylinder to 1200cc.
Pre 1983 OHC 4 valves per cylinder to 1025cc.
Among the eligible V5 machines are the following: Ducati F1A and F1B, 750cc limit; Honda CB750F, CBX, CB900F, pre-1986 Honda VF500, VF700, and VF750; Kawasaki KZ750, KZ1000, Z1, GPZ 550/750/1100, and EX500 without restrictions and regardless of year; Suzuki GS1000, Seeley Suzuki 750, pre-1986 Suzuki GS 750 (no hybrids, i.e., Suzuki GS 1000 motor in a 1985 mono-shock frame), GS 500 (no restrictions); Yamaha FZ600, Seca 550, Seca 750, Virago 980, TZ 750. RZ 350 with maximum displacement of 450cc.

Vintage 6 Heavyweight (these appear to me to be all newer more modern bikes compared to a Rickman frame designed around 1970...)
Pre 1990 Factory road racers up to 750cc.
Pre 1990 OHC 2 valves per cylinder up to 1216cc.
Pre 1990 OHC 4 valves per cylinder up to 1216cc.
Pre 1990 OHC 5 valves per cylinder up to 1100cc.
Among the eligible V6 Heavy Weight machines are the following: Honda Interceptor VF700/VF750/VF1000F and R, CBR600/750/1000, CB1100F, RS250 up to 1990; Kawasaki Ninja 600/750/900, ZX7/ZX10; Suzuki GS 1100F, Katana 1000/1100, GSX-R 750/1100 except 1989 GSX-R 1100; Yamaha FJ1100/1200 and Seca 900, FZR 750/1000 except 1989 FZR 1000, FZR600 (regardless of year), TZ750 alloy frame and mono-shock, TZ 250 up to 1990.
 

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It would most likely be a V5 bike for WERA, if they allow the Rickman frame as production. It could fit in V6 except again it specifically states that the V6 bikes must use the OEM frame. I believe that the Rickman frame fits in the spirit of the V5 or V6 rules. The only definitive answer you can get is from Sean Clarke at WERA, [email protected]. email him and see what he says. I have bikes for both V5 and V6 and I would not protest you in either class. The rules specify that 43mm forks are eligible in ether class. I don't believe that AHRMA has a class where you are legal, except possibly Formula Vintage. That would only give you 1 race per day with them. With WERA you can bump up to a variety of classes.

You may get more responses on the WERA forum in the vintage section.
 

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Discussion Starter #7
I feel as if those classifications are still fairly ambiguous in terms of classifying a Rickman... it was a limited production street machine called the CR or "Competition Replica" (not Cafe Racer as many people falsely claim - Rickman sales literature backs that up).

Honestly it seems as if by those classification wordings above, it could fit into any of those classes legitimately....
Unfortunately it seems as if my little GS425 twin resleeved and bored to 489cc would be substantially harder to find a concrete class description that would be filled with other 500cc pre-1983 twins... too bad, I am quite surprised.
 

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Discussion Starter #8
Ahhhh.... Thank you very much, Ken!

I did read further down and saw some more info relevant to me. The GS425 would likely fit into the broad classification of Formula 500, as they specifically list GS450 Suzuki (1980-1988, 425 was older 1979-only version of that). One of the older pre-83 classes lists the GS500 (Same engine family as GS450, but 1989-2010!!! Talk about vague/ambiguous...)


Formula 500
Pre 1973 2-stroke factory road racers up to 360cc.
Pre 1974 2-stroke production machines up to 500cc.
Pre 1974 4-stroke, 4 cylinder up to 500cc.
Among the eligible Formula 500 machines are the following: Bridgestone 350; Cagiva-Ducati 500cc Panta twins; Honda CB350F, 400F, 500F, CB450 and 500 twins, CB550 and 1977 MT125; Kasawaki H1, H1R, and S3 400cc; Moto-Guzzi 500 twin; Suzuki 500 Titan, GT 380, GT550, and GS450 any year up to 550cc; Yamaha RD350, RD400 (regardless of year), R5, SR500s (up to 540cc), TR2, TR3, TZ 250 and 350

Wow a GT550 vs a GS450... The 450 frame is SUBSTANTIALLY better, but geez a 550 2 stroke would slaughter a GS450 on straight line acceleration!!!
Sounds like a big grid is likely at most events in this class.
 

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Discussion Starter #9 (Edited)
As far as upgrades go:

Suspension: Forks: All machines must use period type forks. Maximum diameter is: GP, V 1, V 2, Formula 500 and V 3 - 38mm. V 4, V 5 and Formula 2 Stroke –43mm.
Upside Down forks are permitted in Formula 2 Stroke, V 5, V 6 and V 7 only.

Brakes: Formula 500, V1, V2 and V3 will employ disc brakes up to 12” in diameter, no floating rotors.
Calipers may be a maximum of two pistons and may float (all components must be period correct).
Formula 2 Stroke, V 4, V 5, V 6 and V 7 may use any brake system provided that the design and operating principle was in use prior to the cut-off date. V 6 and V 7 are the only classes allowed to run six piston calipers.

There is some vague wording. Some are stated as "period type forks" which to me would mean conventional non-inverted forks under the 43mm limit as they are the style of the period forks. Other areas specifically say "period correct ______" which seems more specific to date/era that the "period type" broad description.




It does seem to rule out my use of RF900R forks on the GS425 as there is a 38mm limit on fork diameter in Formula 500... bummer. GS500 forks it is, unless anyone can recommend a conventional rsu 38mm cartridge fork in a shorter height... no floating rotors, but what about semi-floating rotors?

So the RF900R forks still may fit in there but I'm not certain. I will check in the WERA sub forum since Ken has tipped me off that AHRMA doesn't really have a class for the Rickman.
I did note that WERA lists a Seeley Suzuki 750, so a Rickman frame may likely fit in there as well.




Wheel Sizes: GP, V 1, V 2, Formula 500 and V 3 rim diameter will be 18” or greater unless original equipment was fitted with smaller rim diameter. Formula 2 Stroke, V 4, V 5, V 6 and V 7 rim diameter will be 16” or greater.
(DARNIT...I was really wanting to switch the GS425 to 17" rims!!!)

Rim Width: GP, V 1 and V 2 may not exceed 2.75. Formula 500 and V 3 may not exceed 3”.
V 5 may not exceed 3.5” front and 5.5” rear.
(DARNIT...the 3 sets of wheels I have for my V5 and Formula 500 qualifying bikes are all 3.50x18 rear!!!! Looks like I'll have to lace up a 3"x18" rear rim and get some non-floating rotors made up)

I'm still uncertain after reading the rulebook if 95-97 rf900r conventional forks could be used on the Rickman... the 6 piston calipers I have are clearly outlawed in that class however. Luckily CBR600F4i calipers fit. Now if only I could determine if opposed 4 piston calipers were legal for that class, or if I'd need to use 2 piston sliding calipers...

Looks like I may have a couple sets of good vintage upgrade modern cartridge forks for sale if I do race these bikes.
 

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I have the solution ;) you need 2 bikes, one that is 100% period correct and one that is modified right to the tits, then at sign-in time be that last to register, see who is racing what and decide what class you can win in.
 

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Discussion Starter #11 (Edited)
I just started reading the WERA rulebook because I am gearing up to start focusing on acquiring more parts to do a late fall or winter buildup on 3 bikes, the Rickman and the GS425 being two of them. As it sits now, the GS425 is bone stock.


Plans now are:
GS450 or GS850 sleeves & 72mm pistons - 489cc & probably 10.7:1 compression (haven't had JE, Wiseco, or CP pistons made yet but running same pistons from MTC in my 920cc gs750)
Megacycle cams - probably the .380" lift profile maybe mix a .354" exhaust cam in with that. Or Web .395" lift intake and .365"(?) Exhaust cam.
Send head to Rapid Ray's for oversized valve installs at least of GS1000 size or larger. May drop a lot of money on fancy alloy valves to drop weight. Titanium hardware up top of the valves. Might have to go shim under bucket to save weight although I despise adjusting shim under bucket valve clearances...
Head ported a good bit but still trying to retain some low rpm performance
I was going to run some custom twin-racked Mikuni RS34 carbs, far easier to make into a custom 2cyl rack than a set of vm29 smoothbores. I may, however, bite the bullet and go straight for Keihin CR31 carbs since they were very much period correct, come in adjustable width twin cylinder racks already, & I don't think RS34 were available pre-'83 - so they would likely not be legal in the formula 500 class
2 into 1 exhaust
Kerker System K muffler?
Modified clutch basket & extra clutch plates

Chassis:
Additional frame bracing around spine, headstock, & airbox areas
GS1100E aluminum swingarm narrowed to fit
GS wire spoke wheels 2.50x18 front 3.00x18 rear (all 3 sets of my wheels are 3.50x18 rear,have to lace another to fit in the rules, can't do 17" as I planned either, 18" min.)
Possibly do GS500 37mm forks (38mm max allowed in Formula 500), but the 12"/304.8mm rotor limit stomps out the single disc 310mm rotor plan using stock GS500 parts. Custom bracket mods and custom 12" rotor may be necesary, or more likely just go dual disc & try to combine the lighter/shorter gs500 inner/upper stanchions with GS850/1000/1100G dual disc lowers and gs500 2 piston sliding calipers with modded brackets and dual 296mm rotors
I may even go as far as to do a custom cartridge front end conversion to these forks from Maxton just to have a fork as good as the 43mm rf900r cartridge fork I was going to run.
Rear will be vintage Fox Factory Shox. I have 2 sets of piggybacks, 1 set of emulsions. Great vintage shocks.
Pirelli Sport Demon tires 130 or 140/7-18 rear 110/80-18 front.
 
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Looks like a good plan, except for the tires. I would go with some race compound Avons, Continentals or Heidenau. I think the Pirelli Sport Demons, Bridgestone BT45 and the Dunlop GT501, just don't offer enough grip for hard racing use. I run the Avon AM22 front in a 110-18 and the AM23 rear in the 130/65 vb 18. It is a special race profile 130 designed to work ok on a narrower rim.
I also think that bike will fit in V4 and clubman and be competitive, you can run 17" wheels in those classes. When I had my Ascot set up for V2 I had an extra set of 17" wheels I could swap ouy for V4 and Clubman. Especially since the vintage classes run on Saturday and Clubman and DSB run on Sunday.
 
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Discussion Starter #13
Thanks for the advice and encouragement, Ken!
I will definitely consider race compound Avon or Conti rubber. Since the bike will be ridden occasionally on the street, I was only thinking street tires at this point. I may just end up lacing up another front and rear set entirely so that I could run race tires exclusively on those.
As far as having 2 sets of wheels, one 17" & one 18", I'd be concerned with the 1/2" radius difference when dropping to 17" would substantially reduce the trail geometry and make the bike very twitchy if I had the triple offset and rear ride height set up for optimized geometry running the 18" rubber.
How much of an advantage do you see in running 17" rubber? Lighter weight (more free hp) is what I see it as primarily. Slightly less contact patch however. A very miniscule gain in needing smaller triple clamps as you will need less offset in the triples, very tiny weight savings.
 

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Discussion Starter #14
Nice pic! I wonder what class that bike was running in? It has GS500 forks and front brake as I had hoped to run. And 17" wheels. CR carbs, same as I plan to run.
Interesting...the rear set positiin. It took me noticing the extremely long shifter linkage to realize the rearsets are in the passenger footpeg position, quite the stretch! They are fairly short bikes, however...
I am very excited about this project, although a 740cc GS550 comes first most likely. 650 head and cylinders, custom run of Wiseco pistons for the closed chamber 650 head. Fox Street Shox. GS500 front brake setup basically (using ninja caliper sane but opposite side as gs500, & 310mm cbr900rr rotor). 3.50x18 rear rim. I have a very important customer to please (wifey). And also needed to really out-do her latest clunker, a 13000 mile $5000 1986 FX Hardly-Ableson that left her stranded on the west coast. 1337cc pig that only has about 7 more horsepower than a bone stock gs550, can't even do the ton (99 mph top speed), & is slower accelerating than a stock gs550... her wall of death coworker buds have infected her with the harley plague... I need to give her a serious dose of wrist twisting to burning rubber to cure her of that slow poking grandpa & grandma hauling sickness....


Once I get that thing built up with some kz1000 vm28 carbs and megacycle cams and properly jetted, then I can switch back to my projects. I'm building a basement shop at the new house now, so hopefully I can ramp/hoist bikes down there in the winter to wrench on...
I'll post a build thread of sorts when I have actually started on it (wrenching will start on the 3 bikes after Halloween - I hang it up fir the year then after hitting a deer early November a few years back on my gs750. Mating season. Beware.)
 

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Discussion Starter #15
been looking for a gs400 for a few months. View attachment 28010
Did you know a Wiseco GS750-844cc piston will bore right into a gs400 block to make it a 449cc 10.55:1 or so? Longer stroke than the 750 but same piston. 750 stock is 8.8:1 iirc. 400 is 9.1:1 iirc.
If you are looking to go 489 or even 475cc (894cc gs750 piston), let me know. I want at least 1 set of 489cc pistons 72mm, might get a group purchase going through Wiseco for the 71mm 475cc/894cc version.
 

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There's a few thread over on GS Resources about mix and matching GS450/500 and GR650 top ends to make a 500+cc engine. I think the 650 crank, 500 barrels / pistons with the 450 head make the easiest combo (??)
 

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Discussion Starter #17
The compression ratio is fairly low with mist of those combinations. The way to go is 1980+ 450 bottom, 1989-2010 GS500 cylinders, GR650 Tempter cylinder head and cams (biggest of all oem gs twin cams), and custom pistons to correct the compression ratio back up to compensate for the substantially shorter stroke of the gs450 crank vs the GR crank. Maybe it could be possible to mill a lot of material off of the head to bump compression up, but it would be best to just get JE or Carillo to make custom pistons in the desired Compression ratio / dome size.
The GR650 head, much like the GS650 head, is a 2 valve variant on the TSCC 4 valve technology. The early 2v engines were all hemi heads/pistons. The 4 valvers used Twin Swirl Combustion Chambers, TSCC. They called the GR650 a Twin Dome Combustion Chamber head. It is a more advanced closed chamber raised runner swirl port head and piston design.
Rensdw on GSR had Carillo make a custom set of CP Pistons in the mid 10:1 range based on the GR650 head/piston and the GS400 2v crank. He did a serious retrofit running a roller bearing early 2v bottom end and changing the head stud spacing pattern to that of the GSX400/GS450/GS500/GR650... quite a feat to get the earlier longer stroke roller bearing crank. The 500 cylinders are slightly shorter as well, and require some base gasket spacing I believe.

The early gs400/425 had the longer stroke (60mm) and smaller pistons (65/67mm), whereas the GS450 had the shorter stroke (56.6mm) and larger pistons (71mm). The GS500 shared the same stroke (56.6mm) & head stud pattern, but had much larger pistons (74mm).

The GR650 was a big twin at 77mm bore x 70mm stroke.
I suppose one could contact Carillo Rods/CP Pistons and use the info Rensdw posted on his GR650 hybrid pistons, & recalculate the chamber volume, and use his compression ratio and piston dome cc size, and then reverse engineer the amount of piston dome volume that would need to be added to make up for the 60mm stroke vs the 56.6mm stroke. Double check the needed compression height of the piston with the gs500 base gasket, cylinders, and check against a GS500 piston. Then double check the wrist pin diameter vs what Rensdw ordered. There you have it, 10.3:1 or so 527cc closed chamber head GS450 or 500!

The GS500 head does not work with the 450 frame rails, by the way. Major exhaust interference. The GR650 head is the best but most complicated route. I think Rens spent over $800 on those CP pistons. I don't think that was with his custom Carillo rods but it may have been.
Running a GS500 bottom end or at least all internals if they swap to the 450 crankcase would be best, so you are running a crankshaft and balance shaft that was designed for a 74mm flat top piston. Then bore the GS500 cylinders to their max of the GR650 standard size of 77mm.

I think I will stick with a resleeved 425 cylinder block and hemi head and go the easier route to attain 489cc...
 
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