5th gear WOT engine stopping?

hello folks. here's the delima on my friends YSR:

My friends bike was running poorly the other day. he still has the OEM carb with a jet kit and a toomey pipe. his air box has those holes in it to increase air intake. When he WOT on 5th gear, the bike just dies...........it is kinda like acting as if it no longer has fuel in WOT at 5th gear. just shuts down at WOT in 5th gear. he also has the inline fuel filter so we thought that that could be the problem. that the fuel wasn't traveling in a vertical path to the carb from the tank but even though we shortened the fuel line, it still died on WOT in 5th gear. what do you guys think that could be? I've been reading up and some seem to think it's an adjusment on the float tab in the carb. others say that the small flat screw at the bottom of the carb's float bowl may have some deposits in it.......so that I should drain that screw out.........what do you guys think it it could be?

in 2nd gear, 3rd, and 4th at WOT, it runs fine. it's only in 5th gear at very WOT, the engine simply shuts down. stops running. it's like it has no more gas or something.

We cleaned out the carb completely yesterday. the bike now runs better in the lower gears with the newly cleaned out carb but in the last 5th gear, at WOT...........it simply dies and engine shuts off.

can anyone else diagnose this problem?

what altitude are you at? have you swapped carbs maybe? if its wot its usually the main jet or could be air screw adjustment etc. Id swap carbys and put in a new plug and run it 5th gear wot then after it shuts down pull the plug and see what it looks like. I havent messed with these bikes enough to give a way to troubleshoot it but i can give you general diagnosis for a two stroke. Take apart fuel petcock too and make sure theres no crap in there

I'm at approximately 0. I'm at sea level. south Florida. you are basically at the same altitude as the ocean.........sea level.

hummm....we'll have to play with the air screw then. as well as the petcock.
but why would the petcock only affect the WOT at 5th gear?
it may be the main jets. maybe they are clogged? aren't the main jets the ones that operate at the higher gears? at WOT?

YES

Do a plug chop with a new plug and report your findings.

Q? Does it die at WOT in 4th gear, 3rd gear, 2nd gear? Get the idea. 5th gear WOT doesn't really makes sense to me if the bike works well in the other gears at WOT.

This could be an electrical problem.

swap to a good running carb to make sure thats not the issue that will help you with knowing if you need to actually troubleshoot the carb. I usually crack the throttle wide open with the tire up in the air and adjust the af screw till i hear it peak so to say, should be around 2-2.5 turns out, if you have to go more you should use a smaller main jet and if you have to go less you should get a bigger one.

Disregard my questions... didn't fully read the orignal post-I was so sleepy last nite.

I still think it may be electrical. Unplug your lights. If you have a bad battery, it may be drawing on the electricals causing the engine to cut out.