Have a pilot with a broken crank. Parts are very hard to come by. And I have most of them. A guy recently offered me a gsxr 600 motor (( Internal Combustion Engine ? )) he was gonna put in a formula racer. motor (( Internal Combustion Engine ? )) has 5000 miles on it and is complete w all electronics, throttle bodies and pipe for $1000. Wondering how hard of a build it is if anyone knows. motor (( Internal Combustion Engine ? )) seems like a good deal. Is there a better/ easier transplant?

ROTAX IT! And keep your pilot trans. Can't really beat them. Been done countless times with great success. That's what I'd do anyway. should be able to do it for the same or less counting all the fab work. Also if its in your budget or in the near future I'd rebuild the pilot Engine and shelf it for the future to restore its value. Parts won't become anything but harder to find. I'd build the new Engine mount bolt in.

Speaking abought rotating it fatcat that's what you should do to ur other fl350

You can have the Pilot crank rebuilt you know.

Engine swap requires you to modify every system on the Pilot, most the time lowers the value of the Pilot.

Pics of the bad crank?

The big hurdle with the bike Engine, other than packaging, is the gearing. Obviously keeping the Pilot trans is what you want to maintain reverse and the stock axles etc. The output shaft on the bike trans will turn less than half the required rpm to the input of the Pilot trans. My calculations for mine came in a 8000rpm input to the FL350 trans to achieve 60mph, 25" tall tire. The output sprocket on the GSXR,(depending on model year specific gear ratios), will be at about 5500rpm at 13000engine rpm. Because you can't a big sprocket on the bike trans to do the step-up in one shot, it requires a countershaft/dual chain set-up to step up the rpm. The short chains on mine are a weekly maintenace item.
Also ,IMHO, that GSXR 600 is all high rpm power and no grunt. Not the best for off road.

Lots of successfull Rotax swaps out there. That keeps your belt drive intact and gives great bang for the buck power wise. I had a 670 in mine, but to do it again I would do a 470cc liquid if I was to go back to a 2 stroke CVT set-up. Good power in a more compact package.

But I agree with Hoser. If that Pilot crank can be fixed or replaced, you're happy with it's power, and everything else is good with your machine, I'd fix it and ride.