Vintage Road Racing Association

Does anyone know why we don't have 4 cylinder P2's allowed. ?
Miles.

The early 4 cylinder bikes also ran 10 & 13" rims (treaded tires), so they are really front exit P3's. The current P3 rules allow a CB750 based front exit bike on 13" treads. I've got a trick 1030 kit for one.

i am aware of our rules ....But period correct would be to allow 4cyl rigs.
What I was wondering is why we managed to 'shoe horn' our way in to such restrictive period incorrect rules?

I've asked the same question Miles.

Time for a change , I think!!!
I feel a rule change submission coming on.

Miles. The short answer, USCRA objected at the time when VRRA introduced Sidecars to the program!

In the 1970s, CMA rules allowed any motor cycle engine. WERA allowed 1100cc.
Nelson sponsored, Murphy & McCallum CB750 (1100cc)
Brown & Sorenson TZ750
The Steam Roller from Detroit BSA Triple with 20" wheels etc, etc.

Ask the P1 riders of the ERA

I say now as I did then, don't be afraid of the speed & don't be afraid of the competition

Bring on the 4cyinder s/cars!

Tom

Sounds like a good way to make the 12 or so current p2
rigs in our club obsolete in a real hurry...

Btw a TZ 750 is most definitely not pre '72 wtf?

Who had a TZ750?

Oh, sorry. I see you are referring to a previous comment.
I agree. It's not.

Here you go Miles -

11. P3 and P4 SIDECARS
P3 CLASSIC SIDECAR OUTFITS are limited to outfits built up to and including 1972, and outfits constructed after such date that are consistent in design and construction with outfits actually built in the period, subject to the following restrictions:
11a. ENGINES:
four stroke - air cooled only, up to 1300cc*,
two stroke air or water cooled, up to 750cc.
Engines are limited to units built up to and including 1972. 5% overbore allowed. All other engine components shall comply with P3 Superbike rules. * Honda SOHC is limited to 915cc
Examples:
Honda SOHC 750
Triumph / BSA 750 triple
BMW R75
Nourish / Westlake 8 valve
Sunbeam / Hillman Imp
Lavarda 750 twin / 1000 triple
Moto Guzzi
Saab (2 stroke)
DKW (2 stroke)
Crescent (2 stroke)
11b. CHASSIS: to be built of tubular or box section steel only. No stressed skin or monocoque construction with the exception of genuine or copies, in which case the owner shall provide proof of eligibility to the Technical Coordinator
11c. DESIGN: An outfit or sidecar is a three wheeled vehicle leaving two tracks, with only the rear wheel driving, and only the front wheel steering. Driver’s point of contact with steering controls must be rigidly attached to front forks or other steering assembly. Center hub steering prohibited. Swingarms must be two sided, of period design and materials. Both sitter and kneeler designs are eligible. Sidecar chair must be rigidly affixed to cycle portion of the outfit by a minimum of four rigid mechanical or welded connections. Driver must be positioned generally behind engine. Only front exit sidecar designs may be used, and may be on the right or left hand side. Outfit must be equipped with appropriate handholds for passenger, including but not limited to a passenger handhold on the rear outside of the outfit opposite the chair and to the back of the driver.
11d. DIMENSIONS: The two wheels forming a single track must be no more than three inches out of line, measured center to center. Maximum track is 44 inches and minimum track is 32 inches (center to center of tires). Maximum width of outfit is 72 inches. Minimum ground clearance of three inches between any part of outfit and an imaginary horizontal plane beneath the tires, with outfit ready for competition with driver, passenger, oil, fuel and coolant. Maximum fuel capacity 40 litres (10.56 US gallons). Maximum engine offset (measured from a point equidistant between outer pistons to an imaginary line drawn between the centers of the front and rear wheels) 3 inches. No part of the outfit may extend longitudinally more than 12 inches from the front and rear tires. Minimum clearance front tire to outfit 1 inch. There shall be sufficient clearance between the handlebar grips and any part of the outfit, at any time, such that the driver shall not become trapped or not be able to operate the controls.
11e. BODYWORK: Sidecar wheel, rear wheel, and drive and primary chains must be adequately protected to preclude driver or passenger becoming entangled. Period style fairings are encouraged. All bodywork and streamlining must be strictly consistent with the applicable period. Downforce generating devices and designs are expressly prohibited. Driver’s torso and the passenger’s body must be completely visible from above at all times.
11f. WHEELS: minimum 10 inch diameter on front, rear and sidecar, if magnesium wheels are fitted, they must have current crack test certification. Maximum rim width 6 inch.
11g. TIRES: Treaded tires only, maximum tread width 5.5 inches . Tires must be correct fit and size for rim.
11h. SUSPENSION TRAVEL: Minimum 1.5 inch on front and rear wheels. Any sidecar wheel
movement relative to platform is prohibited.
11i. OIL COOLERS: where fitted must be located so as to be generally visible to driver and passenger.
11j. GEARBOX: Exterior and number of ratios must remain as original, internal parts are free.
11k. BRAKES: Working disc brakes on front and rear wheels mandatory; sidecar optional but strongly recommended. Single or twin disc per wheel, provided that all disc brake components (disc rotor, caliper and master cylinders) are components (or functionally accurate reproductions) actually available in the applicable period. No floating rotors. Floating calipers are recommended to reduce the effects due to antidive characteristics of front end design. No four piston calipers. Friction linings and pads are unrestricted.
11l. SAFETY SWITCH: All outfits must be equipped with a functional master electrical switch mounted within reach of both driver and passenger. Switch must be able to stop a running engine and turn off all other electrical systems. The switch’s mounting plate and an area at least 1 inch surrounding the switch must be painted red and clearly identified "ON" and "OFF" for identification by track safety personnel.
11m. OIL CONTAINMENT: shall be by a liquid tight container around the bottom of the engine with a minimum of 3 quarts capacity. Oil absorbing material shall be in addition to the container. The front edge of the container shall be equal to or greater in height than the centre line of the engine crankshaft. All breather tubes from catch cans must be routed into the oil containment container. A low oil pressure light, visible to driver and passenger is required for all engines fitted with plain bearing crankshafts.
11n. SAFETY: All pipes or exhausts otherwise terminating in a sharp edge must have a rolled edge added or a bull ring welded in place.
11o. NUMBER PLATES: See Part A – 2g. Colours must be as follows:
red numbers on white background.

P4 POST CLASSIC SIDECAR OUTFITS are limited to outfits built from 1973 up to and including 1982, and outfits constructed after such date that are consistent in design and construction with outfits actually built in the period, subject to the following restrictions:
11a. ENGINES:
four stroke - air cooled only, up to 1100cc,
two stroke air or water cooled, maximum 4 cylinders up to 750cc.
Engines are limited to units built up to and including 1982. 5% overbore allowed. All other engine components shall comply with P3 Superbike rules.
Examples:
Kawasaki KZ 900 / 1000
Kawasaki H2
Suzuki GS1000/GS1100
Suzuki GT750
Yamaha TZ 750
Honda CB900 / CB1100
11b. CHASSIS: to be built of tubular or box section steel only. No stressed skin or monocoque construction with the exception of genuine or copies, in which case the owner shall provide proof of eligibility to the Technical Coordinator
11c. DESIGN: An outfit or sidecar is a three wheeled vehicle leaving two tracks, with only the rear wheel driving, and only the front wheel steering. Driver’s point of contact with steering controls must be rigidly attached to front forks or other steering assembly. Center hub steering prohibited. Swingarms mat be one, or two sided, of period design and materials. Sidecar chair must be rigidly affixed to cycle portion of the outfit by a minimum of four rigid mechanical or welded connections. Driver must be positioned generally behind engine. Front, or rear exit sidecar designs may be used, and may be on the right or left hand side. Outfit must be equipped with appropriate handholds for passenger, including but not limited to a passenger handhold on the rear outside of the outfit opposite the chair and to the back of the driver.
11d. DIMENSIONS: The two wheels forming a single track must be no more than three inches out of line, measured center to center. Maximum track is 44 inches and minimum track is 32 inches (center to center of tires). Maximum width of outfit is 72 inches. Minimum ground clearance of three inches between any part of outfit and an imaginary horizontal plane beneath the tires, with outfit ready for competition with driver, passenger, oil, fuel and coolant. Maximum fuel capacity 40 litres (10.56 US gallons). Maximum engine offset (measured from a point equidistant between outer pistons to an imaginary line drawn between the centers of the front and rear wheels) 3 inches. No part of the outfit may extend longitudinally more than 12 inches from the front and rear tires. Minimum clearance front tire to outfit 1 inch. There shall be sufficient clearance between the handlebar grips and any part of the outfit, at any time, such that the driver shall not become trapped or not be able to operate the controls.
11e. BODYWORK: Sidecar wheel, rear wheel, and drive and primary chains must be adequately protected to preclude driver or passenger becoming entangled. Period style fairings are encouraged. All bodywork and streamlining must be strictly consistent with the applicable period. Downforce generating devices and designs are expressly prohibited. Driver’s torso and the passenger’s body must be completely visible from above at all times.
11f. WHEELS: minimum 10 inch diameter on front, rear and sidecar, if magnesium wheels are fitted, they must have current crack test certification. Maximum rim width 10 inch.
11g. TIRES: Slick,or treaded tires, Tires must be correct fit and size for rim.
11h. SUSPENSION TRAVEL: Minimum 1.5 inch on front and rear wheels. Any sidecar wheel
movement relative to platform is prohibited.
11i. OIL COOLERS: where fitted must be located so as to be generally visible to driver and passenger.
11j. GEARBOX: Period external castings, or cases, internals are free.
11k. BRAKES: Working disc brakes on front and rear wheels mandatory; sidecar optional but strongly recommended. Single or twin disc per wheel, provided that all disc brake components (disc rotor, caliper and master cylinders) are components (or functionally accurate reproductions) actually available in the applicable period. No floating rotors. Floating calipers are recommended to reduce the effects due to antidive characteristics of front end design. Four piston calipers available in the applicable period are allowed. Friction linings and pads are unrestricted.
11l. SAFETY SWITCH: All outfits must be equipped with a functional master electrical switch mounted within reach of both driver and passenger. Switch must be able to stop a running engine and turn off all other electrical systems. The switch’s mounting plate and an area at least 1 inch surrounding the switch must be painted red and clearly identified "ON" and "OFF" for identification by track safety personnel.
11m. OIL CONTAINMENT: shall be by a liquid tight container around the bottom of the engine with a minimum of 3 quarts capacity. Oil absorbing material shall be in addition to the container. The front edge of the container shall be equal to or greater in height than the centre line of the engine crankshaft. All breather tubes from catch cans must be routed into the oil containment container. A low oil pressure light, visible to driver and passenger is required for all engines fitted with plain bearing crankshafts.
11n. SAFETY: All pipes or exhausts otherwise terminating in a sharp edge must have a rolled edge added or a bull ring welded in place.
11o. NUMBER PLATES: See Part A – 2g. Colours must be as follows:
white numbers on red background.

What other 4 cylinder engines were available in 1972 besides the 750 Honda?

Anything else would have been automotive based - IMP / Honda / Mini, I would think. Z1 was 73, and the next 4 cyl after the CB750. CRMC limits the CB750 to 836cc.