Engine 1.8 8V, CBR 900RR carbs, stock ignition, centrifugal dizzy with vacuum advance unpluged, mechanical fuel pump with fuel restrictor to carbs.
Number of test
slow jet size
idle screws turns out
main jet size
Needle jet height
Results
1
40
3
155
standard
Good idle, no throttle response and low power with bad revving, running hot and too lean
2
40
3
165
standard
Good idle, no throttle response and low power with bad revving, running hot and too lean
3
40
3
180
standard
Good idle, no throttle response and super bad revving and no power at all, really bad MPG, super black spark plugs with carbon fouling, running super rich
4
50
1.5
165
standard
Bad idle, better throttle response and better revving, feels a bit of power, bad MPG, black spark plugs with carbon fouling, running rich
5
50
1.5
155
standard
Bad idle, better throttle response and better revving, feels a bit of power, bad MPG, black spark plugs with carbon fouling, running rich
6
50
1
155
standard
Better idle, better throttle response and revving, feels more power, better MPG, spark plugs with light carbon build up, running rich
7
50
3/4
150
standard
good idle, good throttle response and revving, feels more power, better MPG, spark plugs with light carbon build up, running rich yet
8
50
1/2
150
standard
good idle, good throttle response and revving, can feel the power, nice MPG, spark plugs with very light carbon build up almost unperceptible, running almost normal
At this point i get an AFR narrow band gauge, the numbers at idle was oscilating between 14.3-14.6, at WOT oscilating between 12.3-13, maybe use a 140 mains play with needle heights and see what happens
9
50
1/2
140
standard
good idle, good throttle response and revving, +-25 MPG, spark plugs with no carbon build up, running normal, 14.3-14.6 at idle, 13-14 at WOT
After around 200 miles of driving the spark plugs shows very little carbon build up may be caused by the combination of slow and main jets at middle range throttle so the slow jet was replaced with a 45 size
10
45
2 1/2
140
standard
Not yet, check pending
After driving around 100 miles take out the plugs and it seems OK no carbon build up at all, wet or oil. I think i get the correct AFR mixture, got a decent MPG (~4.5 gal in 100 miles) so i decide use this setup permanently.
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