MulletViper wrote on 03/13/12 at 13:51:36:Over the winter, I replaced the stock air box with something of my own design. I used exhaust pipe of the same diameter as the carb inlet and fashioned a homemade velocity stack.
How long? There's a magic length. My guess would be as long as the rubber ducky that's normally there. But, Diamond Jim found that it was something times the diameter.
Quote: I also cut apart an air filter and attached it to the open end of the intake with a hose clamp.
Took it for a ride today and HOLY COW! She started right up without any choke, which is unusual. Even better, I opened her up and she pulls like a freakin night train.
Got up to 55 in 4th gear and shifted to 5th, BAM! She started to die so I shifted back to 4th.
On the plus side, she didn't backfire a single time, NOT EVEN ON SHUTDOWN. I guess those 4 months of winter tinkerin paid off.
Anywho, I tried turning the petcock to prime, still had the same problem. I'm thinking I need to go up a size with the main jet, but I could be wrong.
My guess is you're rich, and it'll get worse as you go faster.
The air filter will act as a restricter and that spinkter will only get tighter as the air goes faster. Since you velosity stack does not taper, the lead in will have an abrupter velocity change. If you can find a pod filter with a radiused lead in... this would be optimum.
So, replace your round disk filter with a pod filter to add more surface area and to create a gentler lead in.