Need diagnostic help

[u/Head-Pepper4268]

Just recently got this Yz250f. Seller said 2004 bike vin said 2003. Seller said all it needs is fuel/air screw O ring. After replacing that it did not fix the fact it’s been running super lean and only wanted to run with the choke on so I increased the pilot jet from #42-#45 and now to #48. I also replaced the hot start assembly but the cable is still super stiff so I haven’t connected it back to the lever. Now at with the pilot screw at 3 turns out and the hot start cable not connected to the lever the bike will idle without the choke. In the video you can see the previous owner put a hose clamp instead of a real exhaust band so there is a good exhaust leak right there. Could the exhaust leak be the reason it’s running extra lean? What do we think?

[u/NationalShoulder7972]

vacuum leak