LAKEWOOD —Dirt bikes used to be heavy, rough, unreliable pieces of machinery.

The guys who rode them were the definition of gnarly. The rules were minimal and riders often worked full-time jobs so they could travel the country racing for bragging rights.

Members of the Rocky Mountain Vintage Motocross Club are bringing back vintage motocross racing to Jefferson County this Sunday, Oct. 12.

They've modified the track at Thunder Valley in Lakewood to replicate the original, more mellow tracks the old motocross machines once roared over by reducing the taller, steeper jumps and smoothing rough spots.

"This is the first time we've done this, and it's really cool," said Thunder Valley owner David Claybaugh. "The surface will be hard-packed and smooth, versus deep and loamy."

It's not only a chance for the old-school racers to relive their youth, but also offers an opportunity for families and modern racers to sign up on race day to ride a modified pro-caliber track alongside Colorado motocross legends.

"We basically have a class for everyone who has a dirt bike," said club president Morris Herbert, 58. "We've developed a neat culture of people who want to come out, have fun in a laid-back atmosphere and have a chance to race a less intimidating track."

Herbert said the club formed about five years ago and has rapidly expanded to about 250 members who run the gamut from youngsters, families, women and people who haven't been on a dirt bike since Richard Nixon was president.

They race on about seven different modified tracks on the Front Range.

"It's really one of the greatest groups of people you'd want to be around," said Gerry Fostvedt, 54, a pro racer from the late 1970s and '80s. "Vintage bikes cost a lot less than modern ones, and the club is a great way to bring people back into this sport for not that much money."

The Maicos, Elsinores, Bultacos, Yamahas, Husqvarnas and other dirt bikes from the '70s and 80s will be on the track this Sunday. The old bikes often weighed more than 300 pounds, had minimal suspension and shocks and were hard to handle and unforgiving.

"If you come up short and make a mistake, the modern bikes are much more forgiving and won't send you to the hospital like the vintage bikes can," said Larry Flint, a multiple award winner in vintage racing classes.

Fostvedt said he gained his racing chops in Colorado as a teenager in the 1970s before turning pro at the age of 21. He recalls working a full-time job to save money for parts and traveling around the country in a van packed with his racing buddies and dirt bikes.

"Those were fun times in all of our lives," Fostvedt said. "For me, it taught lifelong lessons in core values; I had to work to buy parts, spent time training and competing ... that's something we want to share with other people and have fun doing it."

Austin Briggs: 303-954-1729 or abriggs@denverpost.com