Originally Posted by
Cat 1
OK fellas, Need some input... UP sized the jet (twice) and still lean on the top - The throttle is not "dead" with top end opening so I don't think the venturi is overly big and its smaller than stock... I am turning the Large 18x6 wide APC at 7300 rpm (1500ft pressure Alt). With the jet increase (now at .5mm) I am not able to richen to rpm drop and have "no headroom".. if I pull the throttle back 15% - I then can find a bit of tuning headroom.
I have straight pipe stacks and have a pressure nipple in each side - But i'm not getting any tank pressure - tried variations on the theme (blocking one side) but no dice. I am getting black oil into the Tubing up to the Syringe crap trap but no apparent movement when powering up. Im thinking that my pressure fittings are not capturing pressure and acting like static ports.
Other than that its running great - Added an air bleed (conventional) and it pulled the idle mix up and made it less sensitive.. Just have to find some room on the top .. I could keep jetting up but I think its more pressure related.. Im already "big" for comparative jet size - Just need a little more "push"
How is 7300 for Power on that wide APC Bert?
I am also watching temps with a small IR heat gun - #1 cylinder runs about 5-10 degrees cooler at high power but this cylinder does have a bit less Compression "POP" than the other - I think it slowly improving though...
https://www.youtube.com/shorts/tPN3T341974
You won't get much pressure out of straight open ended pipes... you'll need a larger dia expansion chamber and then the exhaust exit should be the same ID as the header pipes, pressure tap in the expansion section... Or, if you take a look at how saito does their straight pipes on the 130 / 182 twins, they swage the tip down to reduce the exit dia to create some back pressure in the pipe, and then add a pressure tap near the swaged end.