Image: Jeff Crow.

The MX Nationals will retain 250 two-strokes within the MX2 and MXD categories in 2015, Williams Event Management (WEM) and Motorcycling Australia (MA) have confirmed.

One of the most topical subjects of the 2014 season has been the influx of competitive 250 two-stroke entries, which has prompted WEM and MA to implement restrictions on the two-strokes as of next season while remaining alongside the 250 four-strokes.

“From our point of view – and there is a lot of talk about it – our direction is to put in the Supplementary Regulations some level of control,” WEM general manager Kevin Williams told MotoOnline.com.au.

“That will basically be that from the intake manifold to the exhaust port must remain stock [on two-strokes]. So you can put a pipe on, that kind of thing, but it has to remain stock from the intake boot. We’ll pull numerous bikes down at various rounds and we will be checking all of that.”

The supplementary regulations will outline the two-stroke eligibility clauses as follows:
– The 250cc two-strokes will be eligible with certain restrictions.

– The bike must remain in stock trim from the intake manifold to the exhaust port, and all engine parts between those to points and must be OEM for that year model.

– Intake manifold from the rubber boot where the carburetors clamp is and there is no porting or head work allowed.

– For those looking to change swish an extra base gasket will be allowed.

– There are no restrictions on pipes or mufflers other than the fact that they must meet the Noise rules.

– An MA technical representative will be checking engines across the series, and MA will have a head barrel and piston from each manufacturer to compare with.

– Any bikes, found to be modified will be excluded from the results of the day’s competition.

The regulation update comes following major debate across the course of this season, which saw Luke Clout (Serco Yamaha YZ250F) clinch the MX2 crown and Egan Mastin (Husqvarna Motocross Racing Team TC 250) the MXD champion.

Click here for additional details on the 2015 MX Nationals schedule and format following news that WEM and MA have struck an agreement to extend their contract for a further 10 years.