Carburettor Help /advice wanted.

[Wardy]

Carburettor Help /advice wanted.

I have a 1983 Kawasaki Z1000R2 with stock Mikuni carbs on it.

Prior it had pod filters plus a K&N jet kit. However it never really ran right, running lean & hot with a huge flat spot at 3K revs.

I have since stripped the carbs, had them ultrasonically cleaned and put them back together using new stock jets & needles plus the stock air box.
This has seen a loss of power overall but the bikes runs clean and even though the rev range and is so much quieter on the ears, so sort of happy there.

The issue is that the bike refuses to tick over at a nice approx. 1000 revs
Symptoms are:
Start up with choke, no twisting of throttle. Engine runs ok and settles to nice tick over at about 1000 revs.
The minute the throttle is twisted the idle speed starts to creep up, averaging at about 1.5 revs and increases up to about 1.8 revs as the engine gets warmer. Also during riding the engine will not return to low revs quickly in between gear changes, it just sorts of hangs there running fast.

Yes the ide screw has been adjusted, but only effect is to make it run so slow so it stalls or too fast.
The carbs have been balanced and everything seems to be visually synchronised and everything well lubricated and moving ok.

Ralph stuck it on a dyno to try and get to the bottom of the problem, the power output was not as good as I was expecting but the main query that arouse was whilst that the bike ran ok through most of the rev range, at full revs it was running extremely rich to the extent the room filled with smoke and had to stop. !
We are none the wiser.

Anyone got any ideas, the best one being a recommendation of a specialist who can set the carbs up properly for me whilst on the bike…in the Bristol area.
Penny for your thoughts.

Wardy.

[weaver]

the slides and the main air jet will have been drilled when the dynojet kit was fitted which may well cause a problem when putting it back to standard,if its running rich at the top end you need to go down on your main jets

[Wardy]

Thanks Weaver, totally forgot about the drilling regards the dyno jet kit.
Looks like I may well not be able to go back to stock.....so forward it is !

[warren3200gt]

Could be somthing as simple as badly routed cables or air intake between carbs and head leaking.
worth checking the easy bits first. Did you balance the carbs after the rebuild

[Pigford]

Thanks Weaver, totally forgot about the drilling regards the dyno jet kit.
Looks like I may well not be able to go back to stock.....so forward it is !

Just block the holes again - RTV

[Richard L]

Hi Wardy
Just had a similar problem with similar symptoms on my 1100r rep . Same carbs K+N filters dynojet stage 3 . Took me weeks of searching to find the choke bar had moved very slightly causing the choke plungers ( not all of them ) to be partially open. Played havoc with everything though bike still went ok. Tickover all over the place and running on with closed throttle. To check, close choke , pull rubber gaiters back on choke plungers and with a little screwdriver try and move the brass plungers. Just a tiny bit of movement is enough to screw everything up. Weaver is correct , not so easy to go back to standard , thought about it myself a few times.

Richard

[Wardy]

Thanks for the helpful suggestions. Yes I have checked the simple things like air leaks and cable routing, unfortunately all that nice easy stuff is fine.
Can I really just block the holes again!!!

Gona check Richards’s idea about the choke plungers. Rich, if I do find this to be the problem, how do I correct it!!

Thanks.

Gary

[Al]

You cant block the holes off completely they are the lift holes for the slides. No hole no lift. I partially filled mine as mine had been drilled. I used RTV with a drill of the correct size in the hole which was oiled so it did not stick.
You wont be able to do anything about the main air jet on the atmospheric side as i dont think they come out. What you need to look for is swarf in behind them. When they are drilled out no matter how hard you try and any amount of grease the swarf still goes inward. Had to ultra sonic mine to death with the bodies in several different orientations to get it out!
If you are going to ultra sonic clean them you need everything out to include; the emulsion tubes (needle jet) and the pilot jets hidden beneath the removable alloy plugs in the float chambers, the float needle seat with accompanying gauze domed filters!!!!!!

What size main jets, pilot jets are you using and what needle position is the clip on???
Similarly which type of filter in the airbox; genuine kawasaki, aftermarket repro, or a K&N?

AL

[Richard L]

Gary,
If you have the Kwak manual , it is shown clearly on 6-12 and 6-13 . If not loosen the 2 crosshead screws that holds the bar with the choke closed and see If moves any further in and then see if the plungers still move.
If it is anything to do with this your spark plugs will be heading towards being black. What do they look like , are they all the same ?
Richard

[Wardy]

Hi both and thanks for the tips.

Followed Richards advice to check the choke plungers for movement and sure enough there was.
The movement was caused by the starter plunger levers being slack on the choke shaft itself, in turn allowing the plunger to move in and out a little, but only on carb no 1 & 3 though.
I temporary fixed everything nice and tight, put the carbs back on and started her up and got her nice and warm. And …………………still the bloody same.
Settles at nice tick over for about 30 secs then quickly creeps up to 1500 revs or more and sits there. She still revs nice through the range so I am assuming it’s got to be something to do with the choke or low rev bits of the carb (hasn’t it!) But everything looks to be spot on
Richard, yes plugs look to be going towards black but bike has been on stands ticking over for ages whilst faffing about, so can really judge much from this!

So next step will be to follow Zordeds advice and put the holes enlarged by the dyno jet kit back to their proper size.
Zorded, I have gone back to using the stock size main jets & pilot jets and the needle position is the 2nd from top. I have a stock air box and using a K&N filter and an old Harris Magnum exhaust which now sounds far to muted for my ears as it used to be nice and loud with dynojet kit and pod filters.

At the back of my mind though is that if this doesn’t work then I have already sunk about £300 into refurbishing these carbs and cannot keep chucking money away on hunches.

Any other ideas or can anyone recommend a carb expert close to Bristol who could have a final go at properly tinkering with these carbs as I am way out of depth with this, or to keep my sanity and prevent the carbs going under a hammer I may just have to save up & buy a new set of carbs - but what sort!

Gary.

[Pigford]

Any other ideas or can anyone recommend a carb expert close to Bristol who could have a final go at properly tinkering with these carbs as I am way out of depth with this, or to keep my sanity and prevent the carbs going under a hammer I may just have to save up & buy a new set of carbs - but what sort!

Gary.

If you go "NEW" - defo consider RS34 Mikuni

[Al]

Assuming that; you dont have tight valve clearances, blocked air vent in tank cap and do have the correct fuel level in the float bowls, with no splits or perforations in the slide diaphragms etc etc etc.~ start it and run it till its starts to climb and 'pull on' a tiny bit of choke. If the revs drop then its running too weak low down. With the air corrector jet drilled and a 'very free flowing' aftermarket filter like the K&N, and a whopping great hole in the slide body who'd be surprised?
A bit like the effect you get when you have forgotten to turn the fuel tap on the engine begins to race.
You may find that it helps to have a more restrictive filter as those ones are very little more than steel gauze. Seems counter intuitive but to react properly they depend on the restriction of the atmospheric side by the original type of filter. To be fair though i did run mine with a K&N with no issues at all.
Something else i did was to tighten the butterfly return springs by moving the hook onto the next notch round on the mechanism. How 'returny' is the twist grip?
If you take the carbs off again at some point have a look into the inlets and see if you can see any blackening from leaking valves.
When you get them right they are fantastic. There is very little difference between them and my RS 36 Mikuni's in terms of power or how they make it, the biggest difference is what happens when you shut the throttle. CV's by comparison; 'run on', because you cant close the inlets quickly enough. Hence tightening the springs on mine.

AL

[pluto]

If you want to borrow another set of carbs to eliminate engine issues you can try mine. They have the dynojet kit on and are set up to work with k and n oval filters on my Gpz1100 with 1170 kit and unitrac cams, I get no hesitation or flat spots at all. Bike is in bits so no need of them for a few days and I'm 10 miles away in Bath.
Dave

[roosterrs]

I know its not the same bike(mines a 1985 GPz750A3) but I have had issues with poor bike idling and starting after rebuilding the carbs. I am now 99% sure it is the air filter not sitting properly in the air box( standard airbox and new genuine Kawasaki filter).. I think the plastic air box has distorted over time and allows the air filter to lift up/become unclipped from the airbox. Initially I couldn't get an idle properly or start easily. Once i had got is started I couldn't set the idle as it would either die or start revving up, if I adjusted the idle screw under the carbs.I would think I would have set it, rev the bike and then the idle speed would change from where I had set it previously. It would also hang at a higher rpm. After lots of checking and head scratching, as a last resort I pressed on the air filter and the revs shot up to 3000. I could then set the idle properly. I thought I had solved it but then I still had issues starting. It was turning over and firing every so often but not enough to start it. Again the air filter had popped up. When I next went to start it from cold I pressed down the air filter and it started straight away. I have now gaffer taped the filter housing in place as an intermediate cure. The filter cap looks like its fitted correctly but it pops up just enough to cause a problem.
I had ultrasoniced the carbs and had had them off a couple of times thinking it was a carb problem or a problem with the idle circuit. The other symptom I had was no inlet vacuum when I had the vacuum gauges connected. It took me ages to find it to be honest. I am not saying this is your issue, just my experience when trying to solve a carb problem. I hope this helps.

[Wardy]

Sorry for late reply. Just haven’t had time to fetter with the Carbs over the weekend except warm her up and pull the choke slightly….which unfortunately did not have the effect Zorded was looking for.

I am thinking about refitting the dynojet needles but reading up again on CV carbs it shows they have 4 separate but interlinked circuits, being choke, idle, low range and high range, so replacing the needles I doubt will cure my problem which sits firmly in the choke, low rev interface.

Last time I had the carbs off I did check the inlets and they were clean and free of blackening and yes the twist grip is returny enough.

Pluto, thankyou that is a very generous offer indeed but I am confident the engine is fine and if I did borrow them and everything worked well id cry when I give them back.

Roosters, thanks for that prompt. The carbs have been on and off plenty of times so will check this over the weekend once the hangover from the Halloween party disperses.

Thanks All.