A TT-ported [or better still D-ported] Hewland Arrow will leave a BT82 for dead - and not just at the top end either.
  I had several Hewland Arrows back in the 1980s and had nothing but trouble with them.  I appreciate that those I ran had every conceivable bit of tuning you could do done to them including the 5-porting,  and were absolutely on the limit,  but there was too much bottom end trouble [rods,  big ends and cranks].
  A safe starting point for a Hewland,  or indeed any 100cc rotary valve motor running a Tillotson carb is one and a half on the high jet and one and a quarter on the low speed jet.  The kart should start and run under these settings.  If you need to lean in more to get running,  then its likely you've a problem some place else - needle valve on carb,  oil seals,  plug/ignition etc...
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