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

[njwmct]

Just decided to have another look at the Mark II - although my patience is wearing very thin & I may soon be looking for a skip to dump it in

Just had the plugs out 1 & 3 are white - so obviously very lean & I guess causing the idle to hang.

2 & 4 are normal -> sooty.

So again looked carefully for air leaks all around the inlets on 1 & 3 but yet again found nothing.

Totally stumped - absolutely no idea where to look now ?

[njwmct]

I'm having this issue, one day bike running fine after the rebuild, next day, revs hanging. Been following suggestions in this thread and tried most things. Had carbs off, set slides with 0.7mm wire as close as possible following Hymers manual, set float heights with tube gauge. fitted new inlet rubbers. I'm pretty sure I've eliminated any carb problem.
Tomorrow, I'll check valve timing and fit new plugs. If that don't work, its going on ebay.

I know the feeling

[njwmct]

Make sure you have some slack in the throttle cables (especially the return)
Having them too tight will cause the symptoms you describe.

No problems with the cables / freeplay

[Z1Boy]

Give me the old BSA any day.

[Pigford]

Whack another set of plugs in

[njwmct]

Whack another set of plugs in

just put a brand new set in

[Z1Boy]

NJWMCT have you got electronic ignition or the old points set up?

[njwmct]

NJWMCT have you got electronic ignition or the old points set up?

The Mark II didn't have a points set up.
They came with electronic ignition which the bike still has.

[Z1Boy]

Mine is cured 99%. New plugs, even though the "old" ones were new! Manually set slide heights. Adjusted air screws.

I noticed that plugs 3 and 4 looked weaker than plugs 1 and 2, perhaps that would be the cause? Perhaps some fuel starvation? The only common thing to 3 and 4 is the fuel tap and supply so I cleaned the fuel tap filter and checked flow was ok.

Took it for a 60 mile run, and it pulled like a train will look at the colour of the new plugs tomorrow.

Next I'll do a vac check on carbs and see what that's like.

It has 17.5 jets, should they be 20 on a late 74 Z1A? Would 20 be better in any case with STD pipes?

It's now NOT going on ebay..........

[Z1parR]

I'd been tormented for ages with poor running on mine .
After going through all the usual steps and trying various sets of new B8ES's and Iridiums .
I decided to bite the bullet and buy some Nippon Denso Iridiums .
They were a bit dear but instantly better running , not perfect but loads better and i'm sure i can fine tune the carbs now .
Just saying

[njwmct]

Welldone Z1 Boy - that must be a relief!
Didn't go near mine yesterday just decided to take a break from it.
Will get back on it sometime this week.

[wilsonsjw11]

What part number are the Nippon Denso Iridiums for the Z1 please.
Regards
Steve

[Z1Boy]

Two comments on this.

1/ I got a feeling that if you have to use fancy plugs theres some other problem being masked. Perhaps a fault with coils or condensors or earthing, or 12v supply??

2/ I don't get why the slides have to be set @ 0.7mm, when the engine wont tick over at that setting. To get it to tick over, the tick over adjuster has to be adjusted in which raises the slides above 0.7mm anyway. Surely, the thing is to get the sldes set equally. Or is the engine supposed to tick over with slides set at 0.7mm??

[njwmct]

Spent a few more hours on the Mark II today - trying to sort out the hanging idle issue.
Anyhow after messing around for days setting the slide heights numerous times, checking for air leaks & changing plugs etc to no positive result.
I dropped the needles a notch today (back to clip position 3) & hey presto the hanging idle disappeared immediately!!
Weird! - I have absolutely no idea why lifting the needle one notch should cause the idle to hang.
Anyway, now seem to be moving back in the right direction.
I've also stuck with the larger #17.5 pilot jets as they seem to give the best idle.
Went for a ride on the bike & it seemed OK but the acid test is going to be from a cold start to see if the original misfire at 2000 rpm / surging at 3000 rpm is still there or not (the reason that I lifted the needles in the first place).

[Pigford]

If the slides are a bit high - then the raised needles will allow a bit more fuel thru