Get an extra 5% added to your KOR gift card for the rest of the year. Gift cards make great stocking stuffers and can be saved for future projects. CLICK HERE http://kenoconnorracing.com/gift-certificates.php
That screw, and the spring that keeps it from falling out, will come with almost every carb rebuild kit on the market. I have them in stock. Call the shop if you get hung up. www.kenoconnorracing.com
I'm looking for OEM cylinders, cylinder heads, and crankshaft cores that I can rebuild and offer to the group. The better the condition, the more I'll pay. I'm not interested in junk. DM or call the shop to and GET PAID. kenoconnorracing.com
As a general rule. You should go up 1 size for every 30 degrees of temperature drop. For example FMF pipe with open air box and stock Mikuni carb at 80 degrees, at sea level wants a 280 main. Everything the same but drop temp to 50 degrees, you should go up to a 290 main jet.
KOR is now stocking rebuilt OEM cylinders and crankshafts. They're available on my website. Here's the link.
KOR | Used Blaster Parts (kenoconnorracing.com)
Your countershaft is binding on the bearing. I'm thinking dirt is wedged between the shaft and inner race. Take a large C clamp and put a small amount of force on the front motor mount section of the case. LIGHTLY tap the end of the countershaft. Repeat as needed. If the top end bearing fell...