i did a muffler mod on my 290 and it made a big difference. Used it for a few years, then got a 362 c-m. I really like them both, and would be happy with either. Now about the higher octane gas, I've never heard or thought it would make that much of a difference, but now I want to try it out. Sounds like it would be worth it.
I race ATV's and have highly built motors on my quads. So I have to run a minimum of 100+ octane.
VP and Sunoco have good fuels designed with and without ethanol.
Some are leaded and some are unleaded.
Some are oxygenated and some are not.
it's a little pricey at 65 bucks for a 5 gallon can, but its good stuff.
For those that may not know, octane indicates the volatility or flash point of the fuel.
Low octane fuel is much more volatile then high octane fuel.
High compression lends itself to pre ignition. Pre ignition is caused by the heat and compression being so great that a low octane fuel will ignite before the piston reaches top dead center. Causing it to ping, and lose power.
High octane fuel needs a hotter spark to ignite the fuel and resist pre ignition because of high compression ratios.
2 strokes tend to run a minimum of 11:1 or higher.
Yes they will run on 87 pump gas, but high octane fuel works much better.
You don't need to re jet to run VP's U4.4, just mix with your favorite 2 stroke oil and let'er rip.
You will be amazed the first tank full. Your saw will run a little cooler as well.
I ran a highly built race motor for 7 years on that fuel. The only reason for the rebuild was because the trany let loose.
When we opened it up she looked brand new.
On the quad
I bored it out from a 400 to a 426 and had the cylinder molly plated.went to a 14:1 compression and stroked the crank.
Put in a stage 2 cam with titanium valve guides with oversize valves.
Decked the head and ported and polished the head.
Bigger header pipe with a 450 r flat slide carb, bored out 20 thousands, and choke plate removed.
XR heavy duty timing chain and guides and XR timing gear.
All polished main bearings and balanced gear box.
She started stock with 24 HP
She dynoed at 58 HP with the upgrades.
And of course I run strait 100% VP U4.4 or sometimes C110.
You can buy it as little as a gallon at a time, if you want to try it.
However, do "NOT" run it in your car with low compression motors. You'll burn a hole in the piston.