Jetting advice(dyno graph)

[Bikeless]

Hi,
Anybody got any ideas on making my jetting better,i have dynojet kit,blue line is 122 mains,red is 118 mains,see graph.

MY fueling is still a little out and was thinking of 116 mains.

Cheers,Paul

[Kickstart]

Hi

Only issue seems to be towards the bottom end. A different shape needle is probably what is required to lean it off between about 2000 and 7000rpm..

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Bikeless]

Different shaped needle is out of my realms really,just wanted to know if there is anything i can do with the needles and jets i have,

Cheers,Paul

[Kickstart]

Hi

Drop the needle a touch (ie, clip further from the sharp end of the needle) which will improve the bottom end. Might loose you some higher mid range. Possibly go back towards a 122 main jet which might get the higher mid range back and cost you a little top end.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Bikeless]

I finally put in 116 mains in and it feels better at the bottom end but the rest feels pretty much the same except for the exhaust now sounds slightly quieter for some reason.

[rotax81]

slightly quieter as in running weaker.
dude, you cant really gain a lot by messing with what you have.
go back to that last jet and basically do as keith said.
sometimes you can up the idle mixture a bit by the screws and it sorts some low down problems out but the idle will be a bit erratic when hot.
there is nothing like the right jet (the one you have)and the right needle height/shape to get it as near as dammit
____________________
ZX636C6F road. ZX636C1H track. ZX7R redundant. ZX0.5R minimoto as ornament.
Audi A4 Avant 1.9TDi and VW Transporter 2.5TDi 888 Special (no mot and tax lol)

[Pete.]

Since dyno runs are full-throttle the mainjet size will do most of the work. Do a part-throttle run to determine the state of the mid-opening mixture and if it comes-out a bit rich say in the 12's put the 118 jet in a drop the float heights half a mil.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Bikeless]

It's still running within the 13.5 AFR(116 mains) apart from 4000-5000 revs where it ups to just under 14 AFR so i left it as it gives the best torque of 65.64ft/lb.Do you think i would be better jetting back up to 118s then try leaning off the mixture screws?

[rotax81]

[Pete.]

Best to just use the idle mixture adjusment for adjusting the idle/small throttle openings. Using if to compensate for full-power mixture is asking for a headache. TBH I'm no carb expert, so I'll refrain from giving you advice that might be misleading.

Where in the country are you BTW?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Bikeless]

Yeh,it has cv carbs and i'm in the midlands.The problem i had was at low revs the bike was a bit rough up till about 3500 revs which was a pain in traffic on small throttle openings.After 4000 it clears and i was dynoing to get rid of the low rev problem and get my power up at the top end to the best it could achieve.

In doing this the power went up from 115bhp to just shy of 120bhp and the bottom end is better but it now souds less gutsy if you know what i mean.

I suppose it's all much of a muchness but i can't help tinkering,lol.

[Bikeless]

Yeh,it has cv carbs and i'm in the midlands.The problem i had was at low revs the bike was a bit rough up till about 3500 revs which was a pain in traffic on small throttle openings.After 4000 it clears and i was dynoing to get rid of the low rev problem and get my power up at the top end to the best it could achieve.

In doing this the power went up from 115bhp to just shy of 120bhp and the bottom end is better but it now sounds less gutsy if you know what i mean.

I suppose it's all much of a muchness but i can't help tinkering,lol.

[rotax81]

from what i have read so far i would try the 122 jets and drop the needle to get the mid range back. basically as keith said somewhere above
then maybe mess with the idle mixture screws last.
____________________
ZX636C6F road. ZX636C1H track. ZX7R redundant. ZX0.5R minimoto as ornament.
Audi A4 Avant 1.9TDi and VW Transporter 2.5TDi 888 Special (no mot and tax lol)

[Bikeless]

I was thinking of upping the mains and dropping the needles but i thought the needles may only make a slight difference,not enough to compensate for jet size,i need to do more research which is gonna cost me dyno time.

Thankyou for all your replies they are much appreciated.

[Ariel Badger]

Main jet will do nothing at low throttle openings, that is the realm of the needle.
____________________
Bikers make great organ donors, get 115 on your licence today.

[Pete.]

Gotta remember though that the dyno graph will be all at full-throttle.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[rotax81]

full throttle by the twistgrip but the slides will not be on full throttle until the engine is at higher rpm.
____________________
ZX636C6F road. ZX636C1H track. ZX7R redundant. ZX0.5R minimoto as ornament.
Audi A4 Avant 1.9TDi and VW Transporter 2.5TDi 888 Special (no mot and tax lol)

[Pete.]

Yes of course. Slides tend to open very early on full throttle though.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Bikeless]

They do open very early on full throttle because the dynograph picks up on this by being slightly erratic with the fuel printout up till around 2500 revs.It's like the slides chatter up and down a bit till they settle.