10" is probably not too long. I have at least that much + a pressure chamber. Try a 6-8" pressure line and just see what happens. Do you have a pressure chamber?

How long is the inlet to the carb? Try shortening that some if it is more than 3- 4". I know you off road guy's like to have long carb inlet lines for when you end up on your lid, but mine is only about 2" (no filter)- direct from tank to carb in my MRX-4.

Start with all the lines run fuel/pressure lines run direct and see what it does. If it's OK, then try lengthening the lines one at a time to where you want them and see where the problem shows up again.