I'm finally getting to my LT500 and trying to get it going.  I've done a lot of research on jetting and I kind of understand the pilot jet is up to idle to quarter throttle, needle is low-mid and main is mid-full throttle.  I understand I may not have explained that right. 

The issue I'm having is that it idles and run's great when in neutral and the choke is on.  When the choke is off it rev's high then I have to turn it off.  When I ride it, the bikes runs fine with very little throttle and after 1/8 to 1/4 throttle the power just dies off and so does the engine. 

I have to check the jets so I know where I'm starting from and plan to do that on Sunday. 

I'm just trying to understand what is going on.  From my research, my thoughts are that it is not getting enough gas when the choke is off and too much when it is on.  Also it may mean that my needle needs to be moved down a notch or two so that it lets more fuel flow?  Am I understanding this correctly?

I can't even do a plug reading because I can't get passed 1st gear because when I give it more throttle it dies.

I have no idea if it's ported or who did the work.  It has a FMF pipe.  I will have to get sizes of jets on Sunday and will check the bolts on the reed cage and clamps on the carbuerator to make sure they are all tight.  How do I do a leak down test?

I have no idea if it's ported or who did the work.  It has a FMF pipe.  I will have to get sizes of jets on Sunday and will check the bolts on the reed cage and clamps on the carbuerator to make sure they are all tight.  How do I do a leak down test?

Thanks Derrick, I was looking for that video 

Let us know what carb is on it, it will say Mikuni or Keihin most likely. If it is a Mikuni look for these numbers.

43b00 = 87 model year

43b10 = 88

43b20 = 89-90

Those are the factory lt500r Mikuni TM38(38mm) carb numbers and are excellent carbs that can be modified. The Keihins are an aftermarket carb, I personally don't like them they have less tuning circuits.