10:46 2001-08-27
PLEASE HELP ME WITH THIS !!
Hello , my name is Tomas PETTERSSON
I am the President over this V-TWIN Club:
The Swedish Yamaha TR1 / XV 750 Club (XV920 owners is also very welcome).
http://hem.passagen.se/xv750xv1000
I am a owner of a Yamaha TR1 ( known as XV920 in US) which has the same engine ,it is only size  diffrent 981cc compare to 920cc between theese two.
My problem is to build a perfect exhaust system for my 1200cc race engine (TR1 with 10mm more bore then stock).There is only system for stock engine to buy.
The stock engine max rpm is 6500 (Max HP) and my revs to 10.000 rpm and is 20 % bigger then stock as I told you.
Can you be kind to help me to find how to calculate a perfect exhaustsystem consider max throttle respons and of course max power.I have tried a lot of ours on the Internet to find anything , but NOTHING of how to calculate the inside diameter of a system.
I am (very conscius) about the calulation , and what to consider. I am not a newbee at this !!
How fast should the flowspeed be inside the exhaustsystem ? I have heard 120 meter/sek ?
I have now a very bad system , 2 inch inside is TOO LARGE , the stock is much smaller !!
Here is some tecnical stuff about my engine which is very unique !
Go here for a picture of my bike ,here with out airfilter : http://hem.passagen.se/xv750xv1000/tech/maptr1_techtips.htm  
Bore 105 mm     ( Stock 95mm )
Stroke 69,2 mm
Intake Valve: 49mm
Exhaust Valve: 39mm
The Cylinderhead are Maximum Ported with theese valves.
The cylinder head (Intake) flows 320 CFM.
Comp 10,5 :1
Camshaft: Megacycle X3 = 300 degree with 1mm lift (0,4 inch)
The timing : 43 / 77  intake    77 / 43 exhaust
Lobecenter: 107
Lift Intake  12,57  mm (0,495 inch)
Lift exhaust 12,065 mm (0,475 inch)
I use Dellorto 40 mm with acc-pump ,and free-flow own build airfilter and with good funnel which work perfect.

Answer this letter to tr1@hem.utfors.se  OR  nirvanamotorcycles@hem.utfors.se
If you can't help me send this letter further to a person who knows it all !

I knew the is many Bikers out there who wants to know !! Not only my self !
And there is nothing in this subject on the INTERNET !