drive sprocket

I got a new to me 77 xs and didn't come with chains. Its hardtailed tcbro. There's a number 18 etched in front sprocket and I counted rear to come to 34t. Here's my questions How can I determine if it's 530 and not 520 sprocket. Do stock 77 xs650 come with an optional 18t front sprocket? And if...

Hi guys, So I successfully (I think) replaced the seals on the clutch push rod and the drive sprocket. I put the sprocket back on, then the plate washer, then tightened the nut. No oil leaks, but there is a sound coming from the left case that sounds like the chain either scraping, or...