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Discussion Starter · #1 ·
While I have my engine apart, Im going to port it. Im looking for mid to top end power, bottom end isnt much of a concern. To raise my torque curve higher in the revs, what should I do? Should I remove material off of the top or bottom of the intake ports? Should I remove material from the top or bottom of the exhaust port? Should I be concerned with adding material?
 

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Discussion Starter · #4 ·
sesnopro said:
I would send it out.
=$$$$. I do all my work anyways. Ive ported 4 strokes, but never a 2 stroke. Gotta learn somehow.
 

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I asked someone about porting on my elan 250 single and this i what he told me.


for the most part widening the exhaust port will improve power all around. raising the exhaust port will raise the power band and make more peak power. if you flatten the top edge of the exhaust port some you will likely gain power all around. your power band will also probably become more violent. like a light switch. unless you have proper porting tools it will be hard to do much to the transfers. you need to learn about port durations. the difference between the exhaust port duration and the transfer duration is very important its called blow down and it has a lot to do with how well the engine runs. intake mods are easy make the intake port almost as wide as the intake side piston skirt. make sure the gaskets dont overhang into the air stream. make sure carb opening matches cylinder. keep intake tract as short as possible. considering that you sled is a single your exhaust port is probably really low to help keep the torgue up. if you raise it to much you will kill the power and your sled will be slower. i would recomend widening the port to about 70-72 % of bore diameter. and reducing the corners radiuses of the Exhaust port make the top edge a little flatter. keep in mind Exhaust ports that are too tall too flat or too wide tend to reduce piston and ring life. head mods are straight forward you need to be able to find your compression ratio then by cutting the head in certain ways not just shaving it you can increase your compression ratio to match what fuel you want to run. if you can afford to run premium all the time increase compression to run on premium. squish band is usually cut to around .040 in depending on what shape your head is and how wide the squish band is. if you want to learn more about two stroke porting go to www.macdizzy.com join the message board for 10 bucks best ten bucks you could ever spend. also go to www.powersportstuning.com its free to join not many active members yet its a new site but some of the smartest two stroke guys behind the scenes. you need to learn about port durations, compression ratios, squish bands, pipe effects and tuning. carb jetting is also key. learn all you can about hi performance two stroke engines that knoledge will help you learn how to modify them. feel free to ask me any more questions you may have.
for more power dual carbs is absolutly the way to go. I have seen dual carbs as large as 50 mm on vintage 440s. if you can get a mikuni or keihin flatslide in the 38-44 region that will be best for your single for more power.

Hope this helps you out.
 

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Discussion Starter · #6 ·
Thank you very much lynx300. This info is very helpful and will be put to use.
 

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no problem. Just let me know how it works when you done.

I will be porting a 300 rotax single soon, it's going in my boondocking/powder olympique.
 

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Discussion Starter · #8 ·
How do you think the computer will handle it if I port it?
 

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an efi is not ment to be ported, you will have to buy one of those new D&D cpus for it.
 

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Discussion Starter · #10 ·
Ok, I guess I wont be porting much.
What should I expect to pay for a D&D cpu?
 
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