What exactly is the benefit of the worm holes? I plan to do a mild port since im no expert. Just match the skirt and windows and clean the casting slightly. I'm not doing the worm holes, just wondering their purpose.
What are worm holes for?
- Thread starter Unstock240
- Start date
they are called boysen ports named after the man who sold the concept to honda racing in the 70's ,basicly they direct the incoming charge into the small openings directly into the lower transfer jackets sooner instead of drawing it via your intake windows of the piston. this increases lowend -midrange torque and widens the usable powerband some.. most all modern 2 stroke cylinders reed intake style cylinders use this design ,banshees and blasters dont have these in the stock jug becuase they are based off of archaic engineered bikes of the early 70's before this was fully understood ,so thats why its a popular additon when porting the yamaha cylinders
Wow thanks for the detailed response that was very helpful! I couldn't find much info because wormholes are just a nickname.
yes but a BB sleeve kit wouldnt as its part of the casting not really the sleeve .the other aftermarket 240 kits all come with them ,on vitos they are too small and they need opened up alot though to function
From my own experiences most engines do not need the Boysen ports. If the intake window is phased correctly in relation to the crank angle; there is no need for them. Next time you have you reeds off; slowly roll the engine over and watch the intake window in the piston; more then likely at bottom dead center there is a lot of the window exposed. This will allow the engine to scavenge properly through the reed pedals. While adding these Boysen ports can actually hurt the engine performance by adding crank case volume; think about that as well.
Well I added the boost ports in today. It gave the kickstart much more compression, and all around more power. I matched up the windows and knife edged everything. For doing it myself I am amazed at the results.
I ordered a new piston, mine was a bit scuffed. When I get that installed I will take some pics. I was in too much of a hurry to ride 
cool, and yeah.. they make a pretty damn nice gain for something so small...
i had mine done after the first 2 months i had my blaster like 7 years ago.. and i couldn't believe how much that small thing helped...
and yeah! i wanna see some picss!
i had mine done after the first 2 months i had my blaster like 7 years ago.. and i couldn't believe how much that small thing helped...
and yeah! i wanna see some picss!
Similar threads
