Do the top guys own other bikes?

No, they rarely own anything moto related. 

Chad bought bikes to test them out at one point I think when he was doing two two.

I'm sure an unmarked KTM was brought to Tomacs place at some point for him to test before he put pen to paper. Same with Chase, I'm sure a Kawasaki appeared at the sandbox on a day when everyone else was told it was closed for the day.

They are contractors. The OEMs own the bikes.

Some of the guys have things like two stroke project bikes. 

A lot of these top guys aren’t really even fans of moto anymore. When it becomes your job it really sucks the fun and fandom out of it 

I think it'd be quite rare for those top level guys to have any bikes of their own seeing as they've been "brand loyal" to whatever brand supports them from as early as the age of 5. 

The exceptions are probably when a top level rider gets dropped due to injury and has to fight for a ride. Think of Wilson in 2017 going blucru before landing his Husky ride, or J-Mart riding the Kawi 450 to get some seat time between races. 

It would be cool to see what brand a top level guy would gravitate toward based on their natural style. Too bad OEM's would throw a fit over that kind of fun. 

Didn’t Roczen buy a kx450 and have pro circuit build it for him a few years ago? 

They may own other bikes, but they are forbidden from being seen on another brand. Per your example, Eli is currently not allowed to ride a KTM in public until his Yamaha contract expires. OEMs can and will pursue legal action for such an infringement. This restriction applies not only to motocross bikes, but other categories, as well; Eli probably cannot ride a Harley, for instance (Yamaha makes Star Cruisers). He shouldn't be caught on a Sea-Doo (Yamaha makes Waverunners). He shouldn't own or drive a Can-Am SxS ATV (Yamaha makes the Wolverine and YXZ UTVs). 

Famously, Jeremy McGrath was chastised by Honda for riding a Yamaha Waveblaster in 1996. This was before they even made a PWC - they just didn't like that he was on another brand's vehicle at all. 

Which top guys are you claiming aren’t a fan of moto?

He never rode it. 

He was probably destined to, but likely his HEP contract was signed shortly before he got to it.

There is two edge sword here. I’ve read riders try new bikes before making decisions to move. Are these bikes provided by teams? Example, did Eli ride a factory KTM? If so, they clearly are supporting the practice. They must then understand that their own riders may try other brands if considering moving. Perhaps there are some boundaries. As long as its done discretely they are probably understanding. In the case of Eli, the team left him, not the other way around so him riding another brand, discretely, possibly wasn’t even questioned. 
Unless riders have a very private place to ride I don’t see the point of owning another brand bike. 

I wonder if Eli still has that KX 250 smoker that Kawi built for him? 

They just go somewhere private unless they are big enough to own the land aka James Stewart riding a factory Honda 125. They ride the real factory  bike before signing and yes manufactures do it all the time. The biggest thing lately is doing what Craig did with good standings on teams. 

That was a Monster deal and had little to do with Kawasaki.  The bike, if anywhere is with Axell.

They definitely can't ride other bikes and atleast be seen doing so.  There we're issues with guys years ago riding jet skis even, because they were a different brand, even though the sponsoring brand(s) didn't participate in making comparable units. Not sure if it's such a thing these days because we have had some top riders get parts for their skis and they definitely aren't for the brand they ride for on the moto side. 

RC4 never rode the RM before he signed.  So there is one example.  

NO!

Coty shock has like 4 personal 2 strokes that he ownes

“Top Guys” don’t own other bikes while they are full on racing, unless they are championship bikes hanging on the wall.

Many Pros after retiring never throw a leg over a bike again.

It’s nice to see that after retiring some of them have come back around to enjoy riding again. But they hate buying bikes even later out of their own pocket.

For what they paid him he woulda signed to ride a KOVE 450. 

Wasn’t the story that after Reedy put it to RC in SX, he rode the Yami and knew he couldn’t beat him again on the Honda. Meanwhile Suzuki had basically copied the Yami motor, RC jumped to yellow and the rest is history.

I remember Carmichael going over that after his career.

Its funny people claiming factory bike is factory bike and good riders overcome it and can win on anything, while history is full of examples where elite riders reject the top teams and their factory bikes, because they feel it doesn't have what it takes. It's like bike actually matters 😄

Did Prado get a KLR650 to practice on to get ready for his factory kawi?

Carson Mumford has a pretty good collection of bikes and memorabilia on his instagram https://www.instagram.com/carsonmumfordsgarage/?hl=en 

I kinda doubt ktm or Kawi left a bike with either rider but you never know. It would be easier for a guy like Eli to have one and no one know about it though. 

That’s more common than we might think in sports. I had a college roommate who was a pretty high NFL draft pick, and before the draft he was getting letters from NFL teams. One day he got a letter from the Cowboys. Our other roommate told him, and he asked, “Aren’t they somewhere in Texas?”.  It was actually pretty funny, but he never watched NFL games on television or anything like that. 

I REMBER READING THAT, BUT HE SPENT A LOT OF TIME WATCHING SUZUKIS RIDERS ON THE BIKE AND FELT IT WORKED WELL RC ALSO KEPT HIS FACTORY RM250 CHAMPIONSHIP BIKE AND USED TO RIDE IT REGULARLY.

 BEN TOWNLEY ALWAYS KEPT A TRIALS BIKE WHEN HE WAS TRAINING AT RCS. HE ALSO HAD A KX450 AT THE TIME WHEN RIDING FOR PRO CIRCUIT.

What do the factory's do with the championship bikes after the season is over? You see guys like RC, Stew, Gajser and others have these showrooms with their championship bikes on display. I'm pretty sure the teams dont let them keep the factory race bikes. Are those just replicas they have on display? Do the teams build them and give them to the rider or does the rider build it just for display purposes?

There's multiple bikes used throughout a season, so in theory there could be multiple "championship" bikes 

Some of them are complete, but I don’t think this is the norm. Some of there are empty inside(no engine internals or suspension) or swapped to stock /non factory parts.