Just paid $160 with shipping, for complete top end from Moto Man out of Michigan.$50 for bore both cylinders at local race car engine builder. Thats $210 for a complete top end rebuild,not a dime more.
Ihave seen,fuel restrictions from inline fuel filters,that look fine.Gas caps vapor locking,starving the engine of fuel.Was the screen in the petcock cleaned?Its rare,but I have also seen the case crack by the crank bearings,and let gear oil in.
sounds like maybe the side getting hot is not getting enough fuel flow.Check floats and no fuel restrictions.Open the drain screw on the float screw and make sure it drain fuel a good rate,maybe compare the two draining at the same time,are they even.
Save your money and keep the stock carbs,just install throttle overide kit.Your money can be spent in other places for better gains.Like suspension,steering stabilizer.Stock carbs are not bad,or Yamaha would have not used them for so many years.
Just for your info I have ported many banshees and blasters. I even had a ad in the Dirt wheels magazine all one summer in the classifieds.I was not beating up your cylinders.I even said give us some measurements.I will line my 350 up most banshees,win or loose
Like said about looking at exhaust port hard to tell,we need measurements.As for the intakes or the whole thing looks like somebody just did some sanding.I would bet it will not run much better than a stock one.
Doller for dollar thats a good deal ,and alot of people run them.Do you have the mods needed for a bigger carb,and you know you will need bigger intake boots.
Your crank bearing will get worse as time .You noise was probally piston slap.I have seen some noisy motor last quit a while,then the next not.Just remember good 2 stroke oil and the right amount lubricates your bearings.If you can afford to fix the crank now is the time.