Mystery plug

the manual for my bike ,81 kz1000 csr
USA model, states that the pilot Air screw is non adjustable. Question is, what's under the white rubbery plug.
If there's nothing under there how do I adjust the fuel/air mixture ?

Remove plug carefully so to not damage the screw underneath.

The pilot mixture screw is set and sealed at the factory for US emissions purposes ( usually on the lean side ) and no setting is given to deter tampering.
If you pull the bung you will be able to adjust as normal.

The manual states 1 1/4 turns out for non US models. Even though mine is a US model should I start with that, I'm trying to achieve a standard base setting. Everything on the bike is totally standard.. the bike is running lean, currently has 112.5 main jets, they should be 122.5 so I'm gonna change them !
By the way, I'm in the UK and at sea level..

Also, as its at the top front of the carbs ie between the carbs and the engine, doesn't that make it a fuel mixture screw rather than an air pilot screw ?

Looks like someone removed the original plug and replaced it with white RTV.

2.5 turns open is what I use as a starting point for those pilot screws. Once the bike is up and running tweak them until you achieve the highest idle and smoothest running during tip in.

Davey b wrote: Also, as its at the top front of the carbs ie between the carbs and the engine, doesn't that make it a fuel mixture screw rather than an air pilot screw ?

Yes!

Mike

Thanks for all your help guys. The bike already runs pretty well, especially from 3000 rpm all the way through the revs from there. Its just a little vague / fluffy at low revs.
Have got new jets on order to get it back to standard and have also ordered a set of new carb holders as I suspect a minor leak there. Will report back when all is fitted. Thanks again, any more ideas gratefully welcomed..

Well said Nessism, it's just a starting point. It seems a fair few people here seem to think that 2 turns or 2.5 or 4 etc is to be rigidly adhered to. Bollocks.
Idle mix screws are there for a reason, not even the best built engine has the same characteristics in every cylinder so fine adjustments have to be made to achieve a steady consistent idle state. Especially when multiple carbs are in play.
They tried that shit on us here in Australia in the late 70's, it didn't work. People were spewing that they had to pay to have the plugs knocked out just to have their reasonably new cars behave nicely. Should have been a recall in my opinion. Rochester quadrajets and Carter thermo quads were the worst followed closely by Stromberg single and duel throat carbs.
Interestingly, Aussie Z bikes never had idle mix plugs in that era.
I do understand that some of you in the US have to face emission tests and quite rightly don't want to be seen as having the plugs removed. Just before your test reatard the ign timing, works a treat!

Bit of a newbie to carbs, so after I've fitted the correct jets and holders is it a case of warming the bike up first, then playing with the mixture screws one at a time until I get what ? A nice even tickover and low rev response ??
I guess make a note of the current screw positions on each carb first as a default setting ?

Those fuel mix screws are richer as you turn out.
So that's the way you should be going.
You are after smooth response as you say and no popping which would indicate a lean mix..
Set them initially the same at the UK manual setting and you won't be far off.

Is your motorcycle totally standard as manufactured? Air box, filter, exhaust? Have you adjusted valve clearance and checked and adjusted ign timing? Is cam chain tension adjusted correctly? If so that's great, next, do the slides move freely up and down the bore, are the diaphragms soft and flexible as opposed to hard and possibly cracked.
Jets as per FSM? If so you are good to go. Yes ,wait until bike is up to normal operating temp then adjust idle mix to achieve steady idle.
Please don't let anyone talk you into buying a colourtune, biggest load of wank ever. Bit like indexing your lawnmower spark plug!