Z1000 MK2 - Poor running in the 2-3000 rpm range

[njwmct]

Whilst doing the winter cosmetic tidy up.
I took the opportunity to strip the carbs & fit a new set of genuine Mikuni needle jets - as I had problems with these in the past & decided to get a complete new set - Allens peformance got these from Japan Mikuni 258 O-1 as standard
I now have a poor running issue that wasn't there before
The bike starts easily & idles quite well.
The problem is that at first the bike is very hesitant in the 2000-3000 rpm range - also if you hold fixed revs at 2500-3000 rpm you can feel it surging a bit. - take it over 4000 rpm & it pulls like a train.
After about 10 miles the hesitancy goes away but the bike doesn't seem as strong as it should be in the 2000-3000 rpm range - let the bike cool down & the problem comes back.
I have checked the following:
Service Fuel levels - correct
Carb balance - spot on
Carbs are clean with no blocked jets.

I am wondering if the problem is a weak mixture at 2-3000 rpm as it's worse from cold.
The needles are set as standard with the clip on grove 3 from the top - I'm wondering if I should richen things up by lifting the needle by 1 notch ?

Anyone experienced a similar problem or got any useful advice?

[PAULJAC47]

First check all head to carbs rubbers are pliable and soft and you are defo getting a good seal onto the head and are tight around carb bodies, spray some wd40 around the joints and see if it improves.Get a gunson colourtune you can see the mix then..Cheers Paul J

[Pigford]

Sounds a bit lean "low down"

Is the problem at part throttle openings - maybe just where the needle is opening... if so may be worth raising the needle 1 x notch (drop the clip)

[njwmct]

First check all head to carbs rubbers are pliable and soft and you are defo getting a good seal onto the head and are tight around carb bodies, spray some wd40 around the joints and see if it improves.Get a gunson colourtune you can see the mix then..Cheers Paul J

All good - done the WD40 bit & no leaks

[njwmct]

Sounds a bit lean "low down"

Is the problem at part throttle openings - maybe just where the needle is opening... if so may be worth raising the needle 1 x notch (drop the clip)

Seems logical - I think that's what I'll try next

[Al]

Are the needles 'bottoming' in the needles jets and lifting the needles off they're seat / location??

AL

[njwmct]

Are the needles 'bottoming' in the needles jets and lifting the needles off they're seat / location??

AL

Hi Al - I'll take a look

[njwmct]

Quick update.
I have dropped the clip / raised the needles by 1 notch.
Had a test ride & it seems better in the 2-3000 rpm area - although this wasn't from stone cold - will have to see what it's like after sitting overnight.
The idle is not now as smooth as it was, even with a carb re-balance

[PAULJAC47]

Have you got pilot screws set about 1and 1/4 to 1 1/2 turns out?

A Gunsons will let you see idle settings,transition mix from pilot to cutaway/main jet and take the guesswork out of things...

[njwmct]

Have you got pilot screws set about 1and 1/4 to 1 1/2 turns out?

A Gunsons will let you see idle settings,transition mix from pilot to cutaway/main jet and take the guesswork out of things...

I have tried the pilot screw settings at 1-1/4 to 1-1/2 but actually get the best idle at 1 turn out.
Will try to get hold of a Gunsons Colourtune this week.

[Pigford]

Check pilot jets again - may need to return needle clip but go up 1 x size on pilots

[njwmct]

Further Update.
Did a cold start today with very little in the way of warm-up before riding.
It's going well!
No hesitation from 2000-3000rpm & no surging on a constant 3000 rpm throttle.
Lifting the needle 1 notch seems to have done the trick - fingers crossed!!

[njwmct]

Further Update.
Did a cold start today with very little in the way of warm-up before riding.
It's going well!
No hesitation from 2000-3000rpm & no surging on a constant 3000 rpm throttle.
Lifting the needle 1 notch seems to have done the trick - fingers crossed!!

Having now covered a few more miles - I now have a new problem.

The idle sometimes hangs around 1500-2000 rpm but sometimes drops straight back down.

I have checked all the inlet rubbers for leaks but all are air tight.

Would the raising of the needle 1 notch have anything to do with this?
(I thought a hanging idle was a more likely to be caused by a weakened mixture).

As per usual any help or pearls of wisdom ? LOL

[z1bman]

have you checked the slide heights?

[Pigford]

Could be a weak slide spring?

Old carbs are fun especially when they weren't that great from new