.... By carb work I ment replacing carb with larger Mikuni and removing airbox.
A larger carb is not a good idea for your application. A smaller carb would make some sense but is still likely unnecessary. For usable low end, large carbs are poison and a mismatch for near stock engines. Running wide open at 5000 rpm is another matter. The name of your game is optimal mixture at low to medium rpm.
Spend your money on a forged high comp piston - much more rewarding.
As for removing the airbox, if you bolt the filter right to the carb inlet, you will shorten the inlet tract too much and will have a flat spot in the torque curve. Just because everybody takes a photo of this carb setup and thinks it's authentic doesn't make it right. For high speed applications you need a velocity stack and for your off road application you need a piece of radiator tubing (4-5" worked for me) between the carb and filter. That also takes care of the annoying intake noise.
Spend your money on a forged high comp piston - much more rewarding.
To sum up:
Smallish carb + proper intake tract length + decent compression + free exhaust = tractable torque and power for off road plunking
I have a 30mm Amal (came with cycle) and I think it's a tad to large but not too bad.
Peter
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