The following script is from “Enhancing the Bike,” which aired on Jan. 29, 2017. Bill Whitaker is the correspondent. Michael Rey and Oriana Zill de Granados, producers.

The sport of cycling is notorious for its culture of cheating—made most famous by the rise and fall of Lance Armstrong and his use of performance-enhancing drugs. Now when cycling hopes to be cleansed of the dopers there’s a surprising new twist—riders enhancing the bike’s performance. Some professional racers aren’t putting steroids and blood boosters in their veins they’re hiding motors in their bike frames. We followed a lead to Budapest, Hungary, and met an engineer who said he built the first secret bike motor back in 1998. And he told us motors have been used in the Tour de France. Our story tonight is not about the latest drugs the riders are using to cheat…it’s all about enhancing the bike.

Bill Whitaker: Where is the motor in here?

Stefano Varjas: It’s in here.

In a bike shop in Budapest, Hungary, we met Istvan Varjas. Stefano, as he’s known, is a former cyclist, a businessman and a scientist. His most important invention he placed inside this bike. The frame is fitted with a small motor he designed. Add to it a lithium battery that powers it and a secret button that he installed.

Engineer Istvan “Stefano” Varjas and 60 Minutes correspondent Bill Whitaker CBS News

Stefano Varjas: This is first speed.

Bill Whitaker: Uh. Huh.

Stefano Varjas: Try to keep the pace.

Bill Whitaker: Wow!

The sound is mostly the chain and the wheels. He said you can’t hear it on the road and all of his motor designs use brushless motors and military-grade metal alloys.

Bill Whitaker: And how does this work?

This is now the latest version of his hidden motor design.

Bill Whitaker: Unbelievable…

It can be connected to a heart rate monitor by remote control. When a riders heart beat gets too high it sends a signal for the motor to kick in.

We took his hidden motors for some test rides up in the hills above Budapest.

Bill Whitaker: This is like I’m on flat ground.

Bill Whitaker rides a bike with a hidden motor in the hills above Budapest, Hungary. CBS News

It was hard to believe it’s real until I put my feet on the pedals. Harder to believe when I took them off the pedals…

Bill Whitaker: “Hello.”

And still beat the local talent. As you can tell it’s not like a moped. There’s no exhaust pipe or revving engine noise. It’s designed to give a short but powerful boost to the rider’s own effort.

Bill Whitaker: So this is a lower gear or a higher gear?

Stefano Varjas sells complete motorized bikes to wealthy recreational riders for about $20,000. But we went to Budapest to find out who else might have bought a silent, hidden motor for a racing bike.

Bill Whitaker: Do you know, are professionals using bikes like these on a professional tour?

Stefano Varjas: This one, no. This on --

Bill Whitaker: But bikes with motors?

Stefano Varjas: Yes. I know-- I know this.

Bill Whitaker: They are?

Stefano Varjas: They use, yes.

Suspicions of hidden motors are fueled by videos of riders crashing in races. This bike seems to move by itself without the rider.

And the first time anyone suspected they were looking at a motor was in 2010 when a famed Swiss racer sped ahead of the pack at unnatural speeds.

These riders all denied they were using motors and no one had ever been caught until last year. Race officials suspended this Belgian rider after they found a motor inside her spare bike.

Jean-Pierre Verdy is the former testing director for the French Anti-Doping Agency who investigated doping in the Tour de France for 20 years.

Bill Whitaker: Have there been motors used in the Tour de France?

Jean-Pierre Verdy: Yes, of course. It’s been the last three to four years when I was told about the use of the motors. And in 2014, they told me there are motors. And they told me, there’s a problem. By 2015, everyone was complaining and I said, something’s got to be done.

Verdy said he’s been disturbed by how fast some riders are going up the mountains. As a doping investigator, he relied for years on informants among the team managers and racers in the peloton, the word for the pack of riders. These people told Jean-Pierre Verdy that about 12 racers used motors in the 2015 Tour de France.

Bill Whitaker: The bikers who use motors, what do you think of them and what they’re doing to cycling?

Jean-Pierre Verdy:They’re hurting their sport. But human nature is like that. Man has always tried to find that magic potion.

He now thinks that magic potion is a motor like the one designed by Stefano Varjas.

Bill Whitaker: Are you selling your motors to pro peloton now?

Stefano Varjas: Never, ever.

Bill Whitaker: Never, ever?

Stefano Varjas: Never, ever. But I don’t know, if a grandfather came and buy a bike and after it’s go to finishing his grandson who is racing, it’s not my problem.

Bill Whitaker: It sounds like plausible deniability, which means my fingerprints aren’t on this when it ends up in the bike of a professional. I just sold it to a client. What the client did with it--

Stefano Varjas: Is their problem.

Bill Whitaker: --I don’t know--

Stefano Varjas: It’s not my problem.

Bill Whitaker: So if someone came to you and said directly, “I wanna use your invention to cheat. I’ll pay you a lot of money for it,” would you sell it to them?

Stefano Varjas: If the money is big, why not?

He said he got his first big money in 1998 when a friend saw his hidden motor prototype and thought he could sell it to a professional racer.

Bill Whitaker: So your friend said, “With all this doping going on, you’re-- you’re crazy not to try to sell your invention--”

Stefano Varjas: Exactly. And--

Bill Whitaker: “--to these professional--”

Stefano Varjas: He proposed me--

Bill Whitaker: “--racers”?

Stefano Varjas: He proposed me, “Give me this bike and I fix it up, your life.” And it’s happened.

He told us his friend found a buyer in 1998 and Stefano swears he has no idea who it was. He gave us this bank record that shows that he had about $2 million at the time. We also know that he spent time in jail for not paying a substantial tax bill in Hungary. He said whoever paid him all that money wanted an exclusive deal—he couldn’t work on the motor, sell it or talk about it for 10 years.

Bill Whitaker: And you were OK with that?

Stefano Varjas: For 10 years. $2 millions-- if you are in Hungary, if you live in Hungary, if you-- they offer you $2 million to don’t do nothing--

Bill Whitaker: You couldn’t refuse it?

Stefano Varjas: Can you refuse it? I don’t think.

Bill Whitaker: So you believe that hidden motors have been used by professional cyclists since as far back as 1998?

Stefano Varjas: I think, yes.

In France, where cycling is a religion, the newspaper Le Monde said this past December that the timeline of Stefano’s story might implicate Lance Amstrong. Armstrong won his first of seven Tour de France victories in 1999, just a year after Stefano Varjas’ said he sold his first motor. Armstrong denied to the paper ever meeting Stefano in person or putting a motor in his bike.

We asked Armstrong too through his lawyer and he denied ever using a motor and declined an interview.

Former U.S. Postal Service team cyclist Tyler Hamilton and 60 Minutes correspondent Bill Whitaker CBS News

We contacted Armstrong’s former teammate Tyler Hamilton who has admitted to being part of all the chemical doping by members of the U.S. Postal team. And Tyler told us he never knew of any motors on the team back then.

In order to demonstrate the motors existed as far back as 1998, Stefano Varjas suggested to us that we find a carbon fiber 1999 U.S. Postal Service team bike, the same bike the U.S. Postal team used in the 1999 Tour de France. We bought this bike off the Internet and he installed a motor based on his first design into the bike. He charged us $12,000, saying that covered his costs for the parts and labor.

We then asked Hamilton to test out the bike.

Bill Whitaker: You could feel the difference?

Tyler Hamilton: Oh yeah, oh, yeah. It’s not super obvious. You know, you-- all of a sudden, you’re just like, “Ah.”

Bill Whitaker: It seems easier?

Tyler Hamilton: It feels a little bit smoother, yeah. Yeah.

Bill Whitaker: So you could see how somebody could get away with it?

Tyler Hamilton: I could see how teams are doing it. Yeah. I could.

The motor gives a limited boost of power for about 20 minutes. Tyler Hamilton said that much motorized assistance during a race on a mountain road could be a game changer for a professional rider.

Bill Whitaker: What kind of benefit could this motor give a cyclist?

Tyler Hamilton: That’s the difference between winning and losing for sure. For sure.

“I guess we shoulda known this was coming, you know? ‘Cause, I mean, there’s more pressure in today’s cycling world than ever to win.” Tyler Hamilton

Few riders know that better than Tyler Hamilton. When he spoke to 60 Minutes in 2011, he was one of the first to talk openly about chemical doping in the sport. He said riders have always looked for ways to stay ahead of the authorities.

Tyler Hamilton: They’d find-- you know, for a while, they didn’t have an EPO test. EPO increases your red blood cell production. When the new tests came out, you’d figure out new ways around them.

Former U.S. Postal Service team cyclist Tyler Hamilton CBS News

Tyler Hamilton: I guess we shoulda known this was coming, you know? ‘Cause, I mean, there’s more pressure in today’s cycling world than ever to win.

During this car ride in Hungary with Stefano Varjas we listened as he talked on the phone with one of his clients about delivering some new motorized bikes. He said he was speaking to this man, Dr. Michele Ferrari. Ferrari is the man behind the doping programs of Lance Armstrong and other top cyclists. He has been banned from the sport of cycling.

Still Stefano Varjas told us that Ferrari bought bikes with hidden motors in the past three years. We spoke to Dr. Ferrari by phone and he denied buying motorized bikes from Stefano but said he has tested one.

Three-time Tour de France winner Greg LeMond and his wife Kathy first learned about hidden motors in 2014 when Greg met Stefano Varjas in Paris and took a test ride. Greg was outspoken about chemical doping and now has the same level of concern about the motors.

Three-time Tour de France winner Greg LeMond and his wife, Kathy CBS News

Greg LeMond: I’ve watched-- last couple years-- and I’m going I know the motor’s still in the sport and--

Bill Whitaker: You know it is still in the sport?

Greg LeMond: Yeah. Yeah. There’s always a few bad apples and-- because it’s a lotta money.

He is so concerned about it that while working as a broadcaster at the Tour de France he and his wife worked secretly with the French police investigating the motors. His best source it turns out was Stefano Varjas.

Kathy LeMond: I asked Stefano if he would please come and talk to the French police.

Bill Whitaker: Did he? Is he cooperating with the police?

Kathy LeMond: Completely.

Stefano said he told the French police that just before the 2015 Tour de France he again sold motorized bikes to an unknown client through a middleman. He said he was directed to deliver the bikes to a locked storage room in the town of Beaulieu Sur Mer, France.

Stefano Varjas told us that in addition to the motors in the bike frames, he’s designed a motor that can be hidden inside the hub of the back wheel seen here in a video he gave us.

Kathy LeMond: Stefano had said, “Weigh the wheels. You’ll find the wheels. The wheels are in the peloton.”

According to Varjas the enhanced wheels weigh about 800 grams—or 1.7 pounds more than normal wheels.

Bill Whitaker: You could detect it by weight?

Greg LeMond: Yeah. Cycling weight is everything. Your body, your bike. If your bike weighs a kilo more, you would never race on it.

“This is curable. This is fixable. I don’t trust it until they figure out how to take the motor out. I won’t trust any victories of the Tour de France.” Greg LeMond

In the 2015 Tour de France, bikes in the peloton were weighed before one of the time trial stages. French authorities told us the British Team Sky was the only team with bikes heavier than the rest—each bike weighed about 800 grams more. A spokesman for Team Sky said that during a time trial stage bikes might be heavier to allow for better aerodynamic performance. He said the team has never used mechanical assistance and that the bikes were checked and cleared by the sports governing body.

A heavy bike doesn’t prove anything on its own but to Greg LeMond the weight difference should have set off alarm bells. In this case, sources told us, the sport’s governing body would not allow French investigators to remove the Team Sky wheels and weigh them separately to determine if the wheels were enhanced. LeMond said not enough is being done by the International Cycling Union to prevent cheating with motors.

Greg LeMond: This is curable. This is fixable. I don’t trust it until they figure out how to take the motor out. I won’t trust any victories of the Tour de France.