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DannoXYZ · September 2nd, 2020, 11:32 AM

Yes, most likely you'll need to increase mid-range fuel and decrease top-end. That's due to design of 2-1 exhausts in general. They will increase mid-range torque while decreasing high-RPM power. This makes for faster and easier to ride bike on streets where low-end torque matters. While reducing that high-end scream of 2-2 exhausts.

Try:
- unscrewing pilots to 2.75 to 3.0-turns out
- add 1mm washer under needles
- reduce main-jet size by 2 to 4

Check out this thread and dyno-chart for effects of 2-1 exhaust on pre-gen. Dyno shows tremendous gain in 4-7k rpm range, with minimal increases above that.
https://www.ninjette.org/forums/showthread.php?t=13852

For best performance, you'll need dyno-test with AFR or get wideband-O2 with datalogging. On factory 250s, you can get +10% more power just by leaning out high-end mixtures by 15-20% with zero hardware changes. On new-gens, with 2-1 exhaust, they went from 105 down to 98 main-jets and it's still too rich. Using Tyga full-exhaust with straight-through muffler added +22-25% more flow and required dropping mains down to 96 for +22-25% more power. Shows factory mixtures easily have 25% too much fuel in high-end.

September 2nd, 2020, 11:32 AM	#2
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Yes, most likely you'll need to increase mid-range fuel and decrease top-end. That's due to design of 2-1 exhausts in general. They will increase mid-range torque while decreasing high-RPM power. This makes for faster and easier to ride bike on streets where low-end torque matters. While reducing that high-end scream of 2-2 exhausts. Try: - unscrewing pilots to 2.75 to 3.0-turns out - add 1mm washer under needles - reduce main-jet size by 2 to 4 Check out this thread and dyno-chart for effects of 2-1 exhaust on pre-gen. Dyno shows tremendous gain in 4-7k rpm range, with minimal increases above that. https://www.ninjette.org/forums/showthread.php?t=13852 For best performance, you'll need dyno-test with AFR or get wideband-O2 with datalogging. On factory 250s, you can get +10% more power just by leaning out high-end mixtures by 15-20% with zero hardware changes. On new-gens, with 2-1 exhaust, they went from 105 down to 98 main-jets and it's still too rich. Using Tyga full-exhaust with straight-through muffler added +22-25% more flow and required dropping mains down to 96 for +22-25% more power. Shows factory mixtures easily have 25% too much fuel in high-end.