Will77
XS650 Member
Ok I’m sure this has been asked before but I have a 1979 xs650 and I’m gonna be running factory style air filters and straight pipes and I’m sure someone else is doing the same so I wanna know where to start with jet sizes
You are right I just want ugly loud look at me but I want it to run good so is is there like a glass pack muffler that will give a just enuf back pressure to run good?With large exhaust ports the XS motor with no mufflers tends to pull raw fuel ALL the way through the motor during valve overlap at higher throttle openings. A complete exhaust will make for more efficient, better running, as a standing back pressure wave "stuffs" the mix at the exhaust valve, keeping it in the cylinder. There's info on header length, muffler size to make best power around. These motors have been run, tested, researched to death for decades by flat trackers, there's some serious knowledge, development been done.
There you've been warned. You just want "look at me" ugly loud, and poor running for a bar cruiser go for it.
Yeah I'm that old fogy.
Yup stock jetting #135 main jet #27.5 pilot jetAssuming BS38s, start here: go up 3 or 4 sizes on the main jets, go up one size on the pilot jet, raise the clip on the slide needle from the middle position to the second-from-the top position. This assumes stock jetting -- verify what stock jetting is for your year carbs.
Experiment with baffles. A simple, home-made baffle how-to can be found here:
https://www.xs650.com/threads/homemade-baffles-for-short-pipes.26822/
And I like your idea for a homemade baffle I will have to try thatAssuming BS38s, start here: go up 3 or 4 sizes on the main jets, go up one size on the pilot jet, raise the clip on the slide needle from the middle position to the second-from-the top position. This assumes stock jetting -- verify what stock jetting is for your year carbs.
Experiment with baffles. A simple, home-made baffle how-to can be found here:
https://www.xs650.com/threads/homemade-baffles-for-short-pipes.26822/
Ok I made the baffles and love the sound but I was wondering if you still rejet the carbs ?Assuming BS38s, start here: go up 3 or 4 sizes on the main jets, go up one size on the pilot jet, raise the clip on the slide needle from the middle position to the second-from-the top position. This assumes stock jetting -- verify what stock jetting is for your year carbs.
Experiment with baffles. A simple, home-made baffle how-to can be found here:
https://www.xs650.com/threads/homemade-baffles-for-short-pipes.26822/
Only if you need to. Bike probably runs poorly now, with flat spots and spark plugs indicating leanness, so yes, you re-jet. Try what I suggested.Ok I made the baffles and love the sound but I was wondering if you still rejet the carbs ?