It’s big but it’s not to big. I’ve done 2 karts with CRF 450’s Same engine I think? one the first one I centered it on the frame rails so the seat had to come way over. After trying a few times I realized that the best way was to move the seat left and angle the seat slightly toward center in the front. The seat also had to be a little higher than normal.
On the second kart I made up a mount to move the engine further to the right off center on the rails. I moved the sprocket in between the right and center bearing. This allowed the seat to be in the normal position but it throws the side to side weight distribution off. So now you have to much weight on the right rear which I thought would really screw up handling. It effected it but not near as much as I thought it would. The kart turned left nicely but pushed just a little turning right because the weight of the engine didn’t allow it to jack as well. Widening the front on the right side only and adding a notch of castor took care of it. Now it turns the same in both directions and handles well.
Another thing you want to do is mount your throttle cable close to the pivot point on the pedal. You want lots of throw on the pedal for more precise throttle control. My engine is around 60 HP. That kind of power with the torque of a 4 stroke can lighten even lift the front end on hard acceleration and you need to be able to control it.
Big radiator they make a lot of heat. If it’s available for your engine the Rekluse Core EXP auto clutch is money well spent. With that you won’t stall if you spin and you don’t risk turning the engine backward.
I’ll post some pics if I can figure out how to do it on this new improved forum format.
Have fun with that thing but be carefull it’s bruttaly fast and really more power than a sprint kart should have.