Fork upgrades for 1970's superbikes that will fit within vintage racing rules?
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Fork upgrades for 1970's superbikes that will fit within vintage racing rules?

This is a discussion on Fork upgrades for 1970's superbikes that will fit within vintage racing rules? within the Vintage Motorcycle Racing forums, part of the Caferacer.net Forums category; 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 ...

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Thread: Fork upgrades for 1970's superbikes that will fit within vintage racing rules?

  1. #1
    Senior Member Chuck78's Avatar
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    Fork upgrades for 1970's superbikes that will fit within vintage racing rules?

    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
    Last edited by Chuck78; 09-04-2016 at 03:25 PM.

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

  2. #2
    Senior Member TrialsRider's Avatar
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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 I'll shut up now, but am very interested to hear the outcome.

  3. #3
    Senior Member Chuck78's Avatar
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    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...

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

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  5. #4
    Senior Member Chuck78's Avatar
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    Quote Originally Posted by TrialsRider View Post
    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.
    Last edited by Chuck78; 09-04-2016 at 02:04 PM.

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

  6. #5
    Senior Member Chuck78's Avatar
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    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.
    Last edited by Chuck78; 09-04-2016 at 02:06 PM.

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

  7. #6
    Senior Member kenessex's Avatar
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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.
    WERA 119
    CCS 119
    CRA 119
    AHRMA not anymore
    \"Think twice before you speak, and then you may be able to say something more insulting than if you spoke right out at once.\"
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  8. #7
    Senior Member Chuck78's Avatar
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    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.

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

  9. #8
    Senior Member Chuck78's Avatar
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    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.

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

  10. #9
    Senior Member Chuck78's Avatar
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    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.
    Last edited by Chuck78; 09-04-2016 at 03:17 PM.

    '77 GS750 920cc, 4-1, GS1100E swinger, 18" Sun rims, Fox Shox, twinpot dual disc, CR31, Yosh cams
    '74 Rickman VR250MX
    '99 Kawasaki KDX220 rugged terrain ripper
    PROJECTS:
    '77 Suzuki PE250B "Pure Enduro" trail beast, ported, Wiseco, TüBliss, Fox Shox/RaceTech
    '76 Rickman CR GS1000-1120cc roadracer, Yosh cams&4-1, RF900R fork, Works piggybacks
    '79 GS425 489cc Formula 500 racer, Tempter cams, GS650 forks, twinpot brakes, DID rims, GS1100E swinger, Fox Shox
    '77 GS550's 650-740cc susp&brake mods

  11. #10
    Senior Member TrialsRider's Avatar
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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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