engine takes forever to start

Spark plug gap can have a mild effect on starting. Try the gap at .025"

Never use automotive (4 stroke) starting fluid on a 2 stroke. All starting fluid is is either which acts as a solvent inside the engine, washing the thin film of oil off of the parts.
Albeit this is temporary, you still end up with metal on metal with no lubricating protection.
WD40 can be used as a starting fluid for 2 strokes since it is oil based and it actually works pretty well.

Which carb do you have? If it is an NT, try holding the the tickler button down for a second before attempting to start the engine. Warning: holding the tickler down too long will only make starting even harder.

How many miles on it?
What have you modified?
Have you checked for spark/air/fuel flow?
Is the muffler clogged?
Need more info to really help much.

If the other bike starts up fine, no problems, why can't you swap parts one at a time with the other bike until you find the part that is causing the hard-starting issue?