AAHHH - Not Sure?

[Jed]

Ok, here's the issue - ZX9

+5 on adjustable ignition advancer - Needles Shimmed up 1mm.

Up to about 3/4 throttle pulls like a train. Last bit of throttle to wide open nothing / flat, no more pull. Back the throttle off slowly, gets to a certain point and starts to pull again.

Too much advance?
Shimms?
Or both?

Cheers, Jed

[Johnnie5]

look at main jets

prob too lean

check he plug colour

[Jed]

Main jets are good - Haven't changed them.

Only had the prob since I shimmed and did the advancer. Should have done one thing at a time. Not a biggy. I'll work it out

[ozzy1100]

Jed shiming lifts the tapper in the tube so effects main as well
Float hight, pin hight , and jet all effect top end :-)

[Jed]

Thanks ozz - I'll take the shims out and try.

Cheers

[Redmohawk]

If you have opened the exaust dia at all or changed the intake (different filter, cut air box , or installed pods) I'd say jets need increasing. If everything else is 100% the same as before except for advancer and lifting needles I'd still er on running lean.

If its pulling a ok at 75% then starts to fall back lifting the neadle may help but I'd doubt it. By 75% open the needle will effect wot but not by much and the tip of most 90's and later Kwaka needles is non tapered for about 4mm so the wot fuel wouldn't be effected by small (up to 4mm) changes in neadle hight much.

I'd get another set of jets and drilled 0.05 mm bigger leave the neadles as they are now, test ride. If you dont have spare jets let me know whats in it now and I'll rummage around and find a set for you.

[Hillsy]

Also check your fuel filter is flowing fast enough and not restricting filling up the bowls.

IE: get a new one.

[Yella]

When you put the top caps back on you didn't pinch the diaphram??

[Hillsy]

By the way 5 deg advance is quite a lot - won't be affecting the fuelling but it's probably pinging under load.

[Hagarr]

Actually its the opposite, if you advance timing you are opening the valve earlier which decreases cylinder pressure which reduces the opportunity of pinging!

Generally gives better top end with reduced bottom end.

Apologies cam timing that is, not ignition, too many wines.


By the way 5 deg advance is quite a lot - won't be affecting the fuelling but it's probably pinging under load.

[jmw76]

What The???????

A lot of misinformation in here.

Why did you make the changes??????
Did you make any other changes first? eg cam, cylinder head (CR, porting, etc), pipe, etc.
What fuel are you running? What octane is the bike designed to run on as standard.

Without any other enhancements, advancing the ignition and making the mixture RICHER (lifting the needles by shimming under the clip I gather) will just kill the top end.
It might make it feel a little better down the bottom but over all you are likely to be loosing out.

My race engine (GSXR1100) actually runs best with a bit less ignition and a bit less fuel after being modified.

[Jed]

Thanks for all the advice guys - as confusing as as it was. No changes were made to cam, cylinder, pipe etc.

jmw76 - what you mentioned about it feeling better at the bottom end is exactly as it was. When you mention less ignition are you saying small advance, say +2 or +3 or are you saying 'retard' it?

red - currently running the 750 carbs - jets are 200 all the way accross. was running well with this setup.

I removed the shims last night and left the ignition for now. Does go a lot better with the shims out, but not perfect. will fiddle with the ignition next.

[Jed]

When you put the top caps back on you didn't pinch the diaphram??

No pinching

[Hillsy]

I still think you should check out the fuel flow first - 200 mains are huge and it wouldn't take much to starve the fuel at WOT especially as you described it in your first post.

[Jed]

Thanks hills - I'll be getting a new filter today

[jmw76]

Jed, If you have a standard bike, put the ignition back to it's standard setting.
Are the jets you running the standard ones?
You didn't answer the question about why you changed the ignition timing and fuel in the first place.
Are you trying to solve a problem that you have or are you just trying to make it go better?

I see that you are running carbs off another model. Is that correct?

What adjustment do you have on the neddle height? Can you drop them down a bit? On the Mikuni carbs you can move the circlip on the needle to change its height.



Peter.

[Hagarr]

Fuck no wonder you've got no top end you've killed it with too much fuel!

200 Jets ??


I still think you should check out the fuel flow first - 200 mains are huge and it wouldn't take much to starve the fuel at WOT especially as you described it in your first post.

[Dynomutt]

I would set the jetting back to stock initially. What year ZX9R?, as the 98 C model onwards are very sensitive to airbox/float chamber pressure when the fairings/Ramair are removed.
I've had quite a few on my dyno for setting up, which is fairly straight forwards, however a problem manifests on the road where the bike doesn't pull cleanly above road speeds of about 50mph or 80kph, this is due to the float chambers not getting the same pressure as the airbox, the easiest way to sort this issue out is to take two rubber hoses from the float vent Tee pieces between carbs 1&2 and 3&4 and run them straight up into the underside of the airbox by drilling two 13mm holes in the unserside of the airbox, then run the two hoses into the airbox and cut them so an inch or so is protruding into the airbox, slash cut the hose at 45 degrees and face the open side towards the front of the bike.
This will then allow the float chambers to see the same pressure as the airbox in a similar manner to pitot tubes on a blow through turbo. Lots of bikes that run Ramair set ups, can suffer the same issues when the fairings and Ramair tubes are removed, most of the later ZX series and the CBR600 are prone to it, and this modification works well on all of them. Once this is carried out then you can rejet as required for whatever exhaust/filter combo you are using.

[Jed]

Fuck no wonder you've got no top end you've killed it with too much fuel!

200 Jets ??

Checked last night - my mistake - they are 190's. These have always been in.

[Redmohawk]

even 190's seem on the large side, But I've not run a 900 on 750 carbs I'd be guessing. I'd say dyno time or a wide band oxy sensor at the least to see whats going on.

[pav69]

arnt 180 & 190 stock on the 9 .by memory i think my zxr 750 was 170 & 180 bigger jets in the two middle carbs or outer carbs memory fail ,but every zxr i had ran rich anyway i would go 1 down in size with dyno time if i had another one

[Yella]

180 - 190 are stock on the 750

[Jed]

Your right - the ZXR's did come out with huge jets. I did read somewhwere why, but can't remember at the moment.