fitted jet kit to 98 zx9r + dyno graph

[MadKaw]

Nope. it just allows a little more air flow..
With those jet sizes it would be running a little rich anyway so the advancer and mesh mod will definately help. You will loose a little bottom end with the advancer but the upper rev surge and added throttle response is worth it..

[SocialSecurity]

hmmmmmm advancing the base timing would traditionally never take power away from an engines low down power, its usually the low rev range where you notice it most of all - unless its pinging?

[MadKaw]

True, it does add power across the range but with much bigger mains you may notice it more up in the revs.. When I took my advancer out and rode it with the stock one, the biggest thing I felt was the lack of pull up in the revs (and the lack of throttle response, it felt dull) . But then I never rode it below about 6000 rpm..
With 155 mains in mine it wouldn't rev clean past about 10,000 rpm, with 158's it was perfect...
I believe Akro state you don't need to rejet with there full system on the 9... Not sure how true that is ...

[SocialSecurity]

Hmmm well somebody had a crack at mine, as it had 142 mains in it! just like yours


ok ive concluded that 160's on the inner cylinders and 158's on the outer cylinders are just too rich. i took the screen out of the filter, not a lot of difference. the bike is telling me "too rich, too rich!" by the way she chortles under full noise with WOT

tomorrow im gonna chase up a +4 advancer, and i think i might pick up another pair of 158's and 155's... that way i can try using 4x158's, or stagger 155 and 158's... THEN ill focus on getting the float level, needle height and pilot screws perfect... as the factory pro tuning instructions say, get the main jet right first then work ya way down


madkaw, did you ever try staggered jets or just a set of 142's or 155's or 158's etc?


cheers for the info too

[stevew_zzr]

Might not be too rich though, the timing, and the spark plugs are both adjusted to suit the standard fuel ratio (which is probably far too close to stoichiometric for really good power). You would have to look at the A/F ratio to really work out whether its too rich or not.

[SocialSecurity]

Might not be too rich though, the timing, and the spark plugs are both adjusted to suit the standard fuel ratio (which is probably far too close to stoichiometric for really good power). You would have to look at the A/F ratio to really work out whether its too rich or not.

click here - very useful carby tuning guide


using that ive concluded its rich in the top end (to be expected on stock timing and 160/158 mains) and lean in the bottom end (floats at 16mm, not even fuel in the bowls) and also the midrange (needles set to leanest, but with the 160/158 mains it runs like a dog on anything else), but ok in the pilot circuit

but as the tuning guide says, you have to select the right mains before anything else, then work your way down[/url]

[9zer0]

When I fitted my K&N Filter I noticed quite a difference, especially in the sound, I cant remember what jets mine were in the end but I would recommend doing your filter, then jetting afterwards, the filter might make more of a difference than you realize

[SocialSecurity]

mmmm i think ive spent enough so far LOL, gonna stick with the stock filter with the screen removed... bought some shell filter oil and turps to clean it

gonna do that tomorrow when fitting the +4 advancer i picked up today + some 158 mains, from mick hone suzuki... bought 6 jets the buggers charged me for 8 meh

[SocialSecurity]

ok went with all 158 main jets, +4 degree advancer, 14mm float height, 2.5 screws out on the pilots, 3rd clip on the needles...

NOW it actually feels like the bike might have ram air its head shaking in 3rd when gassing it hard


i think i might have lost a tiny bit of the low down snappyness it had after the dyno with 152 outter main jets, 150 inner main jets, 1st clip on the needle, 13mm float height, 2 screws out on the pilots and the stock ignition rotor...

...but theres no way in hell im gonna pull the carbs down again, im happy enough now might get her back to the dyno again to see how she goes.. one day

[SocialSecurity]

ok went with all 158 main jets, +4 degree advancer, 14mm float height, 2.5 screws out on the pilots, 3rd clip on the needles...

NOW it actually feels like the bike might have ram air its head shaking in 3rd when gassing it hard


i think i might have lost a tiny bit of the low down snappyness it had after the dyno with 152 outter main jets, 150 inner main jets, 1st clip on the needle, 13mm float height, 2 screws out on the pilots and the stock ignition rotor...

...but theres no way in hell im gonna pull the carbs down again, im happy enough now might get her back to the dyno again to see how she goes.. one day

[MadKaw]

Sounds like a good set up...

Now all you need is a little work on the head, straight through air ducts, a 520 chain kit with alloy sprockets, toss the clean air injection and she should be good for nearly 150 hp... depending on the dyno of course..

[SocialSecurity]

when you say straight thru air ducts, do you mean tossing the resonators? thought about doing that... also noticed there are little tiny holes on the bottom of the airbox where the ducts come into the airbox (the Y) which im sure are to let condensation drip out, but must be letting a little 'boost' leak out when the ram air is working havent touched em tho


i tossed the air injection, took out the valve thing and plugged the hose comming from the air box and joined the two pipes comming off the nipples on the head up, and put a short length of garden hose between the two pipes that lead into the exhaust air injection ports


dont think i could be arsed getting any head work done... and the first dyno i got indicated that i was getting more drive train loss than other 9R's he had tested (probably due to the chain and sprockets being a tiny bit rusty from sitting still for 6 months between being crashed, sold at auction and then re-rego'd... but they have plenty of life left in them for now


wouldnt wanna suggest to marc from factory pro that such a bike is making 150hp at the wheel he was impressed that the place i got dyno'd at was using "real HP" ... but we dont have any local eddy current dynos or 5 gas EGA analysers like they do

[SocialSecurity]

running 158/155 mains now, needles on 3rd clip, floats at 15mm, pilots at 2 turns

bike has a stonking great midrange again, and seems to pull pretty well up top.. really gotta hang on to the bars and duck right down when redlining 3rd

bike now actually needs choke when its cold, and rolling the throttle on around 4-5k gives fantastic pull the midrange seems just a tiny bit better when cold than when warm... might need half a needle clip leaner, but it will be a long, long time before i pull the tank off again

[MadKaw]

Sounds good, I'd be interested to see the new dyno results now..

[SocialSecurity]

made more changes still... switched to all 155 mains and now the clutch is slipping i guess that means its making better power... that and the crazy top end

need to richen up the floats a little, but otherwise pretty strong... think im about done tuning - finally


need to figure out whats wrong with the clutch tho... pulled it out and the fibres looked fine, measured within spec, the springs were well within spec too, tho some of the steel plates had very small blue burn marks and light scoring... put it back together now and double checked its adjusted ok, but its too wet to test ride