You’re better off porting stock cylinder because the casting and overall performance are better than a aftermarket 44 or 44.7 mm top end. That goes for any top end. Especially the farmertec, Amazon, eBay. If going aftermarket Hyway or meteor cylinders are best option. I just got a 026 with a bad top end. The bad top end was a 25-30 dollar top end kit and the circle clip let loose on the previous owner. So I got it for 50 bucks. Got another cheapo top end. 44.7. But I ported the heck out of it along with modifying the piston some. Out the box the ports needed chamfering badly.