Here we go again!
I have had this tingling after Road America that feels like a void in my time that needs to be filled. I want to get back to street riding, but really enjoyed building my race bike for the Sportsman 750 class. The race bike was built with a mission and purpose and while I do want to finish my other project, I really have fallen out of love with street riding since there really isnt a goal in mind. Ride somewhere, enjoy the scenery, go home. Same with shooting. I never plink or shoot alone, and found competition to be far more stimulating and rewarding. I think the same goes for motorcycling.
With that said, I have some sheckles stashed away that are not earmarked for my current bike, and am planning on selling my '09 Thruxton to fund my new build. I like going fast and I like Honda 750's so what to do? Build a Superbike Heavyweight! Here are the rules outlined from the rule book:
10.8 VINTAGE SUPERBIKE
MISSION STATEMENT: AHRMA’s mission is to recreate and preserve the look and feel of
this important era of U.S. roadracing and to showcase these unique machines. While Superbikes
were based on the same production bikes available in the showroom, period performance
parts are extremely rare or even unavailable; therefore, a limited amount of modern replacement
parts are allowed in the interest of safety, cost containment and competition.
10.8.1 These rules have been designed with the following intent:
a) All motorcycles competing in these classes shall be as visibly close to “production”
motorcycles as possible. All eligible motorcycles shall be based on street-legal
models which were available for sale in the United States and/or Canada.
b) Allow the tuner to have more influence over the performance of the motorcycle by
eliminating the need for special frames, suspension systems and “state of the art”
components to be developed or purchased.
c) To provide racing classes with equipment available through normal commercial
channels, and in adequate quantities.
d) Provide interest to aftermarket suppliers and sponsors.
e) Provide a very distinct look and appearance from the other motorcycles competing
in AHRMA events with strict bodywork requirements.
10.8.2 REQUIREMENTS AND MODIFICATIONS FOR VINTAGE SUPERBIKE
a) GENERAL
1) Model year cutoff is 1982, or like design (see definition in Section 2). Exception:
The model-year cutoff for Kawasaki GPz550 is 1981.
2) Engines and frames must be from the same model.
3) All street equipment must be removed (turn signals, centerstands and sidestands,
mirrors, horn, helmet lock, passenger pegs, etc.). Headlight shell must be
retained. Taillight and license plate bracket must be removed.
4) All motorcycles are to use three green number plates, 10x12-inches in size,
with white numerals not less than seven inches in height with a minimum of
one-inch stroke width. Standard block-type numerals, without serifs, must be
used. Visibility must not be blocked by rider’s foot or leg while racing. See section
9.5.
5) Competitors in the Vintage Superbike classes must comply with all applicable
parts of Sections 1 through 9 of the AHRMA Handbook.
b) ENGINE
1) All engines must use OEM crankcases, cylinders and heads from the period
1982 and earlier.
2) Allowed displacement may be arrived at in any manner (i.e., stroker and sleeve
kits are legal). Aftermarket “big block” kits are not allowed (see 1. above).
3) All round-slide carbs are allowed (Keihin CR, Dell’Orto, Mikuni “smooth
bore” and like design). Flat-slide carbs are not allowed. Pumper carbs may be used, but the pumper mechanism must be disabled. 1025cc four-cylinders may
use carburetors up to 29mm, or the stock constant-velocity carburetors that
were original equipment on that machine.
4) Any exhaust system design is allowed. However, all exhaust systems must be
equipped with an effective silencer. Open pipes and reverse cone megaphones
are not silencers. All exhaust systems must include sound-attenuation material
or devices. Modern canister-type silencers are not allowed. Period-style exhaust
systems are encouraged. See rule 9.3.h.
5) Liquid-cooled or two-stroke engines are prohibited.
c) CHASSIS AND FRAME
1) Frame must be a production model built no later than 1982 (or like design).
2) Frame modifications are allowed (bracing or gussets allowed, steering head
angle may be altered, shock location changed or altered, etc.), but welds and
modifications must be of the highest quality and are subject to scrutiny at tech
inspection.
3) Approved period aftermarket swingarms or accurate replicas are permitted.
Shock location may be changed and OEM swingarm may be reinforced, shortened
or lengthened.
4) Standard shock configuration must be used, but shock(s) may be repositioned.
Remote reservoir shocks are not allowed, although piggyback shocks are.
BMW models may replicate factory Superbikes of the period.
5) Front forks must be of OEM or aftermarket origin, with stanchions no larger
than 41mm in diameter. Anti-dive and external adjusters are allowed. Forks
must be conventional type (no upside-down units).
6) Handlebars must be fitted to the original mounts, and must not be below the top
of the fork crowns. No Clubman bars or clip-ons, except when used as original
equipment.
7) Any wheel diameter from 16-inch to 19-inch is allowed. Maximum rim width:
4.5-inch rear, 3.5-inch front. Wheels may be wire-spoked or mag-style in
either alloy or magnesium. Modern alloy mag-type wheels are permitted. Cut/
machined wheels (Performance Machine, etc.) are not permitted. However, As- tralite and Comstar wheels are allowed. If uncertain as to the legality of certain
wheels, please contact the Vintage Superbike Rules & Eligibility Committee
with questions before making a purchase.
Only single- or two-piston brake calipers are allowed. Front and rear discs,
floating or rigid mount of any material except carbon fiber, are allowed.
“Wave” or petal-type rotors are not allowed.
9) Only treaded modern racing compound tires are allowed. No slicks. Rain tires
are allowed and may be hand-cut. Tire warmers are permitted.
10) Airboxes and toolboxes may be removed or modified.
11) Fuel tank and bodywork must be as found on the same year and model of
the production motorcycle on which the racer is based. Motorcycle must have
original seat, which may be modified or recovered while retaining the stock
seat pan. Motorcycle must have the front and rear fenders, sidepanels and front
fairing as the original production model or accurate replicas. Fenders may be
trimmed to fit tires. No tail sections may be added unless OEM on that model.
12) Only fairings that were furnished as standard equipment on the street model
are allowed. Fairings must not extend below the fuel tank.
13) All motorcycles must use the OEM-appearing speedometer and tachometer
housing (if so equipped). Speedometer and tachometer instruments are optional.
10.8.3 CLASSES
a) HEAVYWEIGHT: Unlimited displacement twins and pushrod triples, and
displacement-limited fours and sixes (see chart).
The displacement limitation with a CB750 is 931, which seems a bit silly given the 1000cc limit for other bikes. Regardless of that, I have unrestricted intake, meaning I can run either Kehin or Mikuni round slides of any size.
Here is the master plan so far:
Frame
-Using my current race frame as I have one in the works for next year for my Sportsman bike (more to come on that later). This will also allow me to use shared parts like rearset brackets and such. There won't be much crossover but anything helps
-Going with an F model tank which I have a couple to choose from. They all need to be rehabbed in some way, but with a longer build time, I can take time to get it right
- F model seat, re-contoured saddle. I will need to find a donor that has a bad seat cover and maybe some bent trim, then I won't feel bad modifying it
Front end
-Up to 41mm forks so thinking early 90's CBR600F2, which are 41mm, right side up, and have nice brake mount points. I still need to make sure this is kosher as I need to run a stock-ish looking front fender. Im not sure if that means STOCK or just a fender that looks stock-ish. Whatever I choose will have full Race Tech internals
-Spondon or AP Racing 2 piston calipers, SS lines, and an adjustable ration AP master cylinder
-I have some cast iron rotors with Honda bolt pattern I was told were Z-Mark(??) but I have seen them on more than one period race bike, and should work just fine
-Wheels will be Astralites, 2.5" front and 3.5" rear, both 18" that I picked up from Frank in a partial trade
-Superbike bars on top of '81/82 AHM pattern triple trees (I really like the look and its a nod to early Honda superbikes)
Rear end
-Calfab swing arm - this is the one currently on my other racer, but will be getting a chromoly unit for that to say within the rules. As I get faster I will get scrutinized harder by everyone and need to keep things right and tight
-Similar brake setup as my other racer, with Brembo P32 caliper, SS line, and Brembo master, running on the same style rear set plate as the other bike
-Race Tech piggyback shocks
Engine
-890 12.5:1 pistons and new sleeves
-Big valve head reworked by Mike (I found a head at Mid Ohio last year that was heavily ported with bigger intakes that I will have Mike breathe on to make sure its all kosher and renew with current made springs and modern seat pressures)
-Big ass lumpy cam - I tried the CX10 from Kenny originally but there was piston/valve clearance issues that would require sinking the valves or more valve pocket work on the pistons than could be done on the custom 62mm units from my other bike
-Balanced and lightened crank with Kenny's rods
-Full-tilt trans, pro cut and ISF processed just like my other one
-Trimmed engine cases
-Power Arc or Dyna 2000 ignition running total loss off same battery style I use in my other bike so charger is compatible
-MessnerMoto cam tensioning system
-Etc, etc, etc, $, $, $, fun, fun, fun
That's all I can think of for now, but I plan on this being a slow burn, and hope to have it ready at least for a few races in 2020. I can scratch the itch with my Sportsman bike for now so there is no rush on this one. It nice to already have some parts so I can start building the front end minus triple trees at my leisure before the other bike even comes down for a new frame. At that time, it will also donate the swingarm. I can start to acquire parts over time such as major engine pieces (head, pistons, crank assembly) as well as the braking components.
