68mph - 82mph Lumpy! - Between 68 & 82mph my Z1000 is lumpy as old porridge

[Jon]

Yeah you cant really go wrong with Dynacoils and Taylor leads! Coupled with a decent ignition module saves sooo many problems. Worth every penny!

[Pigford]

... DYNA ciols are ace!!! But remember... if you want full value out of Dyna coils & Taylor leads, you gotta get the ignition sorted... In other words don't keep the points, fit a Dyna S ignition too!

[The Doony]

Me again....
Still got the problem. Can't imagine it's electrical cos when I open the choke the problem clears. Any thoughts on that?
Also, yesterday I took the carbs off again, the manifold rubbers look fine. I dropped the bowls which were spotless. Took out the jets and they all seemed clean but I blew them through anyway. Took it out today and I've still got the problem...this is really starting to pee me off now.
Just to cover the problem again....between 65 and 80 I have a nasty flat spot. If I drop down a gear and open her up she flies no probs, if I open the choke at 65 the problem clears.
HELP!

[Rich]

At what revs is 65-80? did you check the emulsion tubes for blocked holes? What carbs are you running? Try raising the needles a notch. What are your fuel heights like?

[The Doony]

Not sure what the revs are...sound stupid, sorry. I'm assuming that the emulsion tubes are the long brass tubes, they seemed fine to me. I wanted to avoid taking the needles out as it will mean blowing another ?50 on balancing...
Not sure what my fuel heights are like but I was told they were set correctly a few months ago, and all the plugs are roughly the same colour so the problem is across all carbs..at least I think so.
The only things that have changed from before when the bike was running properly is there are now hoses running down from the breathers ( I think thats what they are ).
Would crap in the fuel tap cause this problem? I'm not sure as the problem is only at the stated speed. I think the carbs are 26mm.
The bike was running perfectly with these carbs, jets, filters etc....but I took them off too clean and well, the rest is history!

[Pigford]

If doing about 70mph, open throttle fully for a few seconds, then slowly wind her back. If she gets a bit better, shes running weak! This is because over 1/2 throttle its all on main jet, and the more you open throttle, the more air is flowing in. If gets worse.. too rich. The needle won't effect this bit. BUT... if its jumpy on small throttle openings, the needle may need tweaking. To make mixture richer, move the circlip on the needle - DOWN! This will raise needle, allowing more fuel through for the same given throttle position. If she runs OK when going down a gear & blasting her, main jets can't be too far out? I agree its more likely to be fuel, not sparks.

(Edited by Pigford at 6:47 pm on April 29, 2006)

[Rich]

"there are now hoses running down from the breathers"
How many are there? If three one of them is a vac take off and not a breather, are they kinked?

Yes the emulsion tubes are the long brass ones that hold the main jet - are the holes clear?

[The Doony]

Pigford, I'll hopefully take her for a blast this afternoon and try what you suggest, but it looks like I'm gonna have to fork out for a balance again doesn't it?
Rich, there are 2 hoses which are not kinked, would these have any effect on my problem - as I said they were'nt on b4.
Yes, the emulsion tubes, as the rest of the carbs are spotless.

Would the tap filter cause this problem?
Thx

[Pigford]

Doony, doubt if you'd notice the balancing when doing the speeds you've got problems with. Get the rest sorted before worrying too much about balancing, this usually only effects 0 - 1/8 throttle.

[The Doony]

Pigford, thanks. Can you answer these...
There are 2 hoses which are not kinked, would these have any effect on my problem - as I said they were'nt on b4.
Yes, the emulsion tubes, as the rest of the carbs are spotless.

Would the tap filter cause this problem?

[Rich]

The hoses are for the breathers, for a carb to work the pressure at the venturi has to be lower then the pressure in the float bowl, if the hoses are blocked or kinked stopping the pressure being at atmospheric the carbs will not work properly as the pressure differentials are not correct between the fuel head (floatchamber) and venturi (needle valve outlet).
If there was a third spigot for a hose it would probably be for a vacuum tap takeoff, if this went to atmosphere it would cause it to run lean on that cylinder.
Your tap filter should be clean anyway, if it is not you will run lean at the top end.
What setting did you put your needles in on?
What main jets are you running?
Does it happen when accelerating or when you roll the throttle off to cruise?

[The Doony]

The needles are on the middle notch. Not sure what main jets but I'm about to take the carbs off again to adjust the needles.
It happens when throttle off to cruise.

P.S. Just checked the jet sizes....looks like R 710? It's jetted for a Kerker and was running fine with these.


(Edited by The Doony at 6:15 pm on April 30, 2006)

[Rich]

You should be alright at that. the Mains is probably R110
Who set the fuel heights? When did they set them?

[The Doony]

Floats were set by a local garage about 4 months ago.
I've just changed the needle heights, down one notch. Not able to try it as it's just started pissing down....so I'll have to wait for a change in the weather.
Also, I think I adjusted the needles without upsetting the balance. I didn't need to touch the 2 adjusters....fingers crossed.

(Edited by The Doony at 7:17 pm on April 30, 2006)

[The Doony]

Update...
OK, took it for a blast this morning...SORTED!!!!
Everything seems to be fine now, I say 'seems' cos these things have a habit of coming back. But I think I'm gonna be ok with this one.
Thanks for all your input.
I think it was raising the needles did the trick.