Originally Posted by caferacer
Now exactly what do these changes do?
Widening the inner portion of the exhaust does what?
Raising the roof does what?
I really asking for the info more or less for my knowledge on 2 strokes.
I think you have your kit set-up really well I just need more info about port timing and how it works.
Think of the engine as an air pump. You're increasing the transfer area. This allows more gas/air in and out of the engine = more efficient engine = higher rpms = more power. This is why boost ports increase rpms.
To do this without a head kit:
1.Remove your base gasket if possible to achieve tighter squish = more compression.
2. Raise the roof of the transfer ports between 1mm to 3mm depending on what kind of results you want. 1mm for slight rpm increase, 3mm for large rpm increase. Don't change the angle just the height.
3. Raise the exhaust port the same dimension as the transfers. You can lower the very middle of the floor so it is flush with the crown of the piston. This will create a "D" shaped e-port.
This will not only increase rpms, but it will move the engines powerband higher up in the rpm range. Meaning if your powerband kicked in at 5,000 rpms stock, it may kick in at 9,000 rpms now. This means you will loose low and mid power unless you have an adj clutch or you increase the compression by adding a head kit. This is a very basic description and you should start by making very small incremental changes if you have not done this before. Hope this heads you in the right direction though.
The book is called "Two-Stroke Performance Tuning"
by A. Graham Bell. By far the best 2 stroke tuning book available. Be warned it is dense in calculations and theory, but all have been proven and have shaped todays HP 2 strokes. Check it out here and click it and read the 1st chapter and be amazed! lol. http://www.amazon.com/exec/obidos/tg...glance&s=books
**** you Blah, you beat me to it again! LOL.