I have a friends 800 RMK that bogs or lags off the line when you pin the throttle.  I have a mechanic that has rebuilt the carbs, Clutches, added Boysen reeds and SLP Boost bottle, but the lag remains.  This sled was purchased used and apparently the previous owner tried to handle some mods himself.  The most visible mod done was the air box.  The engine has 135psi in each cylinder and when it finally gets up to about 6k rpm the power really kicks in like a switch has been turned on.  Could it be the jets or maybe the exhaust valves?

The sled is used above 7000 ft.

The clutch with a new stock spring engages at 3000 rpm?

Thanks for any input...

i would verify the ignition is advancing properly, cracking it open with out the proper ignition advance loads the motor till enough rpm's are hit to clear the excess fuel and start making power, lots of things in play, wrong heat range plugs, plug wires breaking down internaly, coil not putting out proper voltage that it shoud,,, really sounds like a timing advance problem to me

mick