arrrrgh!
shut up about back pressure! its a myth perpetuated by ignorance!!!
a REAL TWO STROKE EXHAUST CREATES NEGATIVE BACKPRESSURE.
they can achieve a half atmosphere of vacuum! this SUCKS out the exhaust gasses!
a real two stroke exhaust, also, confusingly, creates POSITIVE BACKPRESSURE (or just plain back pressure) also around, roughly, half an atmosphere.
this pushes any fresh air/fuel that happened to get sucked out with the exhaust, back into the cylinder, compressing the mixture. 21 psi instead of standard 14 psi is a lot of boost. try setting a car with a turbo to 7psi boost and see how it goes compared to stock with no boost at all.
now, the question.
a homelite chainsaw. what capacity is the engine? any idea what the port timings are? is it reed valved or piston ported? these are things you really need to know.
a tuned pipe is tuned to a specific design of engine. capacity, port times, intended rpm.
there are very few bolt on upgrades, except for things common enough. a HT is common, so there are pipes available. a yz250 is common, there are a variety of pipes available, where as a chainsaw with a tuned pipe would just be awkward to use...usually the muffler is at the front, and thats where you bang up against tree trunks, so a pipe a foot longer than the bar would be in the way...
all you can do is find out its capacity. then look around at pipes intended for bikes, scooters, whatever of roughly the same capacity. dont expect full out performance, but do expect a fairly large gain! they arent tuned for what you desire, or what the engine may require. but then a few centimetres of extra pipe or 2 or 3 degrees of ex port opening only affects a few hundred rpm...whereas a 20 degree difference and 20 cm would make a massive difference...
ps, they are easy to make.
