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4 stroke motor work is a lot more expensive than an air-to-spring conversion. If you’re looking to retain a stock bore with a 250 and get yourself a built motor I highly suggest dialing up 3-4 well known builders with all of your questions. A 250f with a built motor is a lot of upkeep and a lot harder to resale on the private market.

I've had great luck with the combination of a cylinder works big bore kit and the GYTR head on yz250f's. I've had this combo on my 2021 for years and before that did the same to a 2015. I go to an aftermarket clutch when I do it, but I'm a clutch abuser. Other then that I have not ran into any reliability problems. Solid power, that still runs on pump gas and isn't relying on more rpms or anything. Its power is not a 350, but its alot more then a stock 250. As far as the cam chain...

I'd call XPR and Twisted Development (TD) and explain what you're after and see what they recommend. I know near us in Colorado there is a guy named Bruce (?) Sass, but I think he's retired. I understand he does still do work by appointment, however. That said, XPR and TD are super tuned into the latest bikes and what you're seeking.

Have you gone all the way down on timing map? If not, set the fuel to the smooth map and then bottom out the timing. If it's too smooth you can always add more timing back in. After 5 years of the Yamaha tuning app I find a happy setting for fuel and then just use timing to adjust the power.

Hey Austin, yes I came off the 23 Husky. Sold it after 15 hours because I just couldn’t get comfortable when the track got dry and rough. If I was you, I’d try comp all the way open then adjust rebound to fit your style. If it’s still stiff, then it’s springs. Or oil level. My suspension is valved by Enzo from previous owner. Check out some data from suspension acquisition I mounted on my bike last week. Fork was with clickers wide open Vs shock is like 4 clicks from closed. In my opinion rear is soft(or correct), front...

I have had luck smoothing the power out by adding fuel to every position and reducing ignition in every position, but also adjusting the throttle % value on the map. Take a look at the maps on Keefer's site to see the throttle % value's he used in his maps and mirror those. My favorite so far is simple, just +3 on fuel and -3 on ignition across the map with lower throttle % values like the Keefer maps. This has a little more power than the smooth map, but feels more linear and smooth across the range. This will...