750 - Exhaust and intake duration in degrees

[iceman_ca]

Hi All:

I'm fairly new here but in am starting a build, which involves putting a GT750 engine in a 89 Katana frame.
Part of the project will be fabing up some expansion chambers.The stock pipes extend out to far and hit the front tire, besides that they look quite odd on the new bike.
I have a program to get the actual cone sizes but I need to input the Exhaust and Intake durations in degrees. Do any of the experts on the site have this info readily available. The program also asks for secondary transfer port , and rear boost ports durations. Both of which i have already entered "0".

I am more then happy to share the results with any one who is interested. The program is variable from track settings to mild street pipes and everything in between, so several pipes layouts can be made.

Thanks in advance

[tz375]

Hi Iceman,

The programs available on the web will produce a pipe design but they are rarely optimized. You are correct that there are no secondary or boost ports on a stock motor. I'd suggest that you think about the porting you want first and then get the barrels ported and then work out the best pipe to work with the revised porting.

We find that stock porting is not where everyone thinks it is, so it's best to check your own.

The software I prefer for chamber design is Bimotion and costs about 200 Euro, and the best simulation software to fine tune teh pipe design is probably MOTA which about $200AUD.

[tz375]

A cheap way to get the port timing is to bolt a timing wheel to the crank end. Use a ten thou feeler gauge to determine port closing/opening times. Obviously the head has to be off and the rest of the motor together for that.

I'd be very interested to see what pipes you come up with. Keep posting as you make some progress.

[iceman_ca]

Thanks for the reply

I will do just that. This weekend I hope to have the cradle fabbed up and the motor mounted in place.
At that point i will pull the head and get some measurements. I really thought the duration on a stock engine would not very much from engine to engine, hence the question.

[tz375]

It's not so much that the timing varied from one motor to another (which they do) but that the timing is not where people think it is. That's why I suggested that you measure the motor you have.

[merckid]

what program did you buy? i bought the 2 stroke wizard pipe design program. I entered all the values to what i thought were correct and it gives me some crazy dimensions. For now i have given up on trying to design and fab my own pipes...i don't know if you are aware but you can actually buy expansion chambers for your motor...im not sure if they would fit into/around your katana frame though? i would also suggest that you buy a program for cone design...i downloaded a free trial program that works really good and i think is perfect for what you are trying to do...if you do some searching around on the web you should be able to find a program no problem. Good luck! you have a long road ahead of you!