Lately my bike has been running kinda weird. When I roll on the the gas or cruise at any speed the bike will get jerky like its not getting constant gas. but it dose not  do this all the time sometimes it will run great with no problem. Also it seems like the bike runs better on prime than on the on position. Dose anyone know what could be the problem and if it is a cheap easy fix.

Thump, I am dealing with the exact same problem on my '87.  I got a bonus, though.  If I run it in the "ON" position, I get fuel leaking around the top of the carb.  Reading this board, I was convinced that the petcock had failed.  My dealer seconded that, so I've ordered a new petcock.  

It should be here in a week or so.  From the accounts everyone here has given, I'm pretty confident that this will cure what ails me.  Hope all goes well for you on yours.

-Jason

When I bought the bike the guy told me that he ran the bike on prime so that is just the way that I have been driving it. Last night I move it to the on position and took it down the rode to see how the bike ran and sure enough the bike cut off less than a mile down the rode. Dose this prove that the vacuum line is bad or is it the entire petcock.

Mine was doing the same thing. I did what  the guys here said to do about the vacuum hose, enriched it a bit and now she's cooking.

Next thing to check is the petcock and float valve.

There's a drain valve in the bottom of the carb.  1. put a cup/bowl under it and open it up with the petcock in the on position.  You should get a cup of gas.  2. turn the petcock to prime and gas should start to come out.  If it comes out in a dribble, somethings plugging it up.  to further isolate it, take the fuel line off the carb, still a dribble?  then it's the petcock.  comes out good, then it's the float valve.

Added to what verslagen1 said, I'd put some seafoam in the gas tank.   Good luck with your problem!

It looks like you need to take your carb apart.

I think there's a screen in the float valve seat, take that out and look for brown trout.  But a good general cleaning is in order.

well I got the carb cleaned an there was alot of gunk on the float screen. In the process of taking the carb off I thought I would wait and put the new cone air filter on that i got, when it comes in the mail. I was wanting to take the air box off of the bike and just run the cone filter. I took the air box off today and and found alot of oil and gunk in the bottom of the air box, is that normal or do I have a bigger problem no my hands?