Another possibility...LSN too lean.
When you lean the HSN,you need to rich the LSN for cooling. Remember those two needles are just like two cocks. The HSN is the master cock which control the whole fuel flow. So we also call it main needle. But the fuel flow is too big when idling,so designer give it another needle to limit the fuel flow when idling. The LSN is just like another cock which only has effect when you close the throttle. Hope you understand my poor English.

Well,for "example";
when your main needle has 0.28 c.c./sec flowing rate,and the LSN limit 50% fuel's flow when idling. So the flowing rate is 0.14 c.c./sec when you close the throttle.

But you feel your engine is not fast enough. So you plan to lean the main needle(HSN) to 0.22 c.c/sec. Ok,it has top speed now but you find the engine temp raised a lot. Because if you don't rich the LSN,the fuel's flowing rate is 0.11 c.c./sec now when you close the throttle. If you want to have the same flowing rate 0.14c.c/sec the LSN only can seal the sprayer 36%.(64% open)

If you don't want to lose the top speed, don't want to rich the main needle,then you need to rich the low speed needle for cooling.

BUT if you feel you need more low end torque after you rich the LSN,What you should do? Adjusting your centax clutch. Saw many racers have this issue. Why they lean their LSN so much because they want more torque. But when the weather is very hot,lean LSN let your engine overheat. When you need more torque,please adjust the clutch first. I usual rich the LSN as possible as I can then I can lean the HSN more. FYI