Eligible machines

Yamaha road-going 250 & 350 parallel twin two-strokes. Includes "LC", "YPVS", "TZR" and "TDR" models. Only models of the same spec as the officially imported model. Reverse cylinder or V-twin model TZRs are not acceptable. Models with larger rim sizes or brake diameters than the official models are also illegal. Model 2XW-1 swinging arm, shock and linkages are permitted as these were officially fitted to later model 2MAs imported to the UK .

 LC Model is RD250LC & RD350LC
TZR Model is 2MA and 1KT parallel twin

TDR Model is 3CK and 2YK
YPVS model is RD350YPVS

We introduce a blanket limit of 59bhp at the rear wheel for all eligible models using the Bemsee supplied Dynapro Dyna and tested at race meetings through the year. RD/LC and YPVS – TZR guidance still apply regarding modifications and components that must remain standard - All RD250 and 350 LC and YPVS models bikes to be dyno tested on spec throughout racing calendar using Dyno facilities provided by BMCRC race club – the reading on the BMCRC dyno is the class guide and no other supplied readings will be used in the event of bike testing.  The clerk of the course has the final decision should a bike not comply to the regulations

1 - Parts that must remain standard 

• Frame and Subframe (No lightening, bracing, or geometry modifications are permitted) ***See section 2f for permitted frame modifications****

• Swinging arm (lower run chainguard must be added)

• Wheels (bearings may be changed for higher specification units)

• Wheel spindles

• Master cylinder (hoses and discs may be changed). LC models may use calipers and master cylinders from any eligible model.

• Petrol tank (internal filters and taps may be removed)

• TZR250 /TDR250 Carburettors (although needles and jets may be changed).

• Ignition system, although static timing may be changed.

•  Engine castings

• Primary drive gears

• Gearbox 

• Clutch (may be fitted with an extra plate or stronger springs)

• Crankshaft

• Rear Shock Absorber (although provision for re-gassing is accepted)

• Powervalve Control Unit and servo motor unit

• The ignition control unit must be the same as the official import model (no re- mapping or FIII kit boxes are permitted), as must the YPVS control unit if fitted.

• RD350LC forks and front wheels may be fitted to RD250LCs to accommodate twin front disks. This mod is not permitted for other models.

• Electrical components may be re-located and fitted with additional waterproofing.

2- Standard parts which must remain, but may be modified

• Rotor may be lightened
• Connecting rods. LC models may use rods from YPVS models.
• Cylinder barrels and head
• Forks
• Rear shock absorber (provision may be made for re-gassing). LC models may use any suitable item from any source. We permit the fitting of alternative springs to the standard shock.
• Minor frame modifications are permitted to allow the fitment of steering dampers and assist in cosmetic improvements and bodywork fitment. As long as those modifications fall outside of section 1a definitions (Typically removing lugs, adding brackets,/flanges) 

3-Parts which may be removed 

• Charging system including regulator/rectifier may be removed
• Speedometer, Speedometer drive, and cable
• Oil tank and pump
• Chainguard
• Mudguard
• Sprocket cover (may be removed or modified)
• Airbox (may be removed or modified)
• Thermostat
• Kickstart mechanism
• Rear brake fluid reservoir
• Equipment for road use (mirrors, horn, indicators, rear footpegs etc.)
• Ancillary frame brackets originally to support road going parts (fairing mounts etc)

 4 - Other modifications

• Rebores to a maximum oversize of 2.75mm. No big bore modifications are permitted
• No additional fairings or streamlining may be fitted which alters the original silhouette. 'Double Bubble' screens may be fitted.
• Race plastic is permitted, including any generally available seat unit which does not need to conform to the original silhouette
• Steering dampers permitted
• All fasteners may be replaced with items of a higher specification than standard
• Exhausts may be modified, or replaced with any aftermarket item on TZR/TDR 250 Models
• We allow the use of non standard or modified exhaust pipes for use on RD250LC, RD350LC and RD350YPVS models to comply with 59bhp limit
• We allow the use of non standard or modified carburettors for use on RD250LC, RD350LC and RD350YPVS models to comply with 59bhp limit
• All machines must comply with the appropriate noise regulations.
• Handlebars may be modified, or replaced with aftermarket items. They may be remounted in any safe position.
• Rear suspension tie-bars may be modified or substituted to modify the ride height.
• Alternative fuel filler caps may be used but must conform to relevant ACU regulations
• We permit the fitment of the Yamaha “Blue Spot” model front caliper for TZR / TDR models
• We permit the fitting of TZR250 wheels/forks and brakes to RD/LC models.  If adopted then the standing regs over callipers and master cylinders will apply and only a single TZR front disc may be used. TZR rear wheel must be fitted to existing RD/LC swing arm
• In addition to the section “Parts that must remain standard “ bullet 3, the optional use of a standard fitment 3.5” rear wheel for TZR / TDR machines is permitted. TDR models are also permitted to use standard fitment front and rear TZR wheels.  Any parts that, in the future, become especially difficult or expensive to obtain, will be subject to a vote of approval for change to a designated aftermarket or alternative part(s). The changes will be decided by ballot under the rules of the constitution.
• Any systems designed to affect horsepower readings during dyno testing are strictly prohibited
• Redundant electrical systems are not allowed and in addition powervalve systems must be fitted and fully operational
• Frame / swinging arm modifications aimed at altering geometry and or providing additional stiffness over standard are strictly prohibited (typically bracing and headstock modifications)

 5 - Tyres

• Only moulded pattern tyres may be used. No wets, slicks or cut slicks are permitted.

6 - Fuel

• Any generally available pump fuel, typically “super unleaded”, premixed if necessary with 2 stroke oil. Octane boosters and other additives are not permitted.
  Max RON - 97

 6 -Technical Inspections

• To aid enforcement of these regulations technical inspections will be performed for the full duration of the season; the coordinators are responsible for selecting bikes for inspections. Inspections will be carried out by volunteers under the guidance of the technical officer or other coordinator. Inspectors have the right to refer issues to the BMCRC scrutineer’s if necessary. Inspections will occur at any point during a meeting at the discretion of the coordinators. Riders are expected to be present throughout the duration of the inspection.