Kawa ZX7r 1997 Carb problem --- Im going crazy here - Please

[azazelus91]

Hi Guys.

I am having a really big problem with this bike.

The bike was off for 2 years. I decided to take the carbs off and clean them. I spent 2 days cleaning the carbs and now i think they are ok. I checked and did the float heigh 13 mm for each carb.

Now here we go.

I did the mixture screw 2.5 turns. I installed the carbs back on the back ( no air filter). I pulled the choke to 100% and push the button. The engine starts for 2 seconds then dies. I have to repeat this step 10 times and then the engine will stay at 1500 rpm idle speed with choke 100% off. After the bike is warm the engine will idle fine at 1500 and throtle is working fine.

This problem with bike not starting correctly it was before i took the carbs out and clean them.

So.... i took the carbs out again and set the mixture screw at 4 turns. When i tested again something weird happened .. the bike will rev very high at 7 k rpm and when i push the throttle the bike goes craze at 10 000 rpm and stays at 10 000 couple of seconds and then goes down really slow. BUT the bike starts now with no problem at all from the first time.

I took the carbs out again and i did the mixture screw 3 turns. Now i have the same problem as previous step with 4 turns but idle is around 3000 rpm. When i push the throttle it goes crazy again like is sucking air from somewhere. Now i thought that there is a leak on those 4 rubbers between engine and carbs but i checked them and i also tighten the collars and i dont think i have any leak there.

Now what should i do? Should i go back with 2.5 turns ?

I checked the pilot jet is fine. I checked the valve needles ... for me they are looking ok. I could not get the seating valve body out ( i dont know how to do it and i was afraid not to brake it ) but i sprayed a lot of air and carb cleaner inside.

The throttle cable is not stuck and the choke is working fine.


The high idle and when i push the throttle the rpm will go down very slowly is a problem caused by any air leak? Rich mixture?

Please HELP.

Thank you

[azazelus91]

anyone?

[Fizzer Thou]

Having had a second read of this problem,I would be looking at the choke plungers to see if any are sticking.A squirt of WD40 will help.

Check also to see if the very small 'O' rings on the air screws are damaged.If you are letting in too much fuel via these,the symptoms would be similar.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[azazelus91]

Hi

thanks for your reply. When i opened the carbs the mixture screw O rings were fine.

I will remove the mixture screw again today and i will check it again.

I dont think it is the choke because when i pull it the bike accelerates and when i put it off the bikes rpm goes down.

The problem is starting the bike on cold... with choke 100% on. It starts then it dies and i have to repeat this 10 times till the bike starts properly.
This is with 2.5 turns in mixture.. if i go higher the bikes starts but idles high and when i pull the throttle it acts like it gets false air from somewhere ( the rpm goes up really high -- even if i pull the throttle a little-- and goes down really hard ).

and i dont get it... maybe i should change those rubbers connecting the carbs tot he engine? .. i checked them inside and there are no cracks or missing parts... the collars screw are a little messed up but .. still i can screw them till the end-- and i think you dont need them to screw them 100% .. i think the rubber is holding the air out.

I was think at something else... because every time i remove the carbs for fixing the mixture screw and put them back in the bike behaves differently... maybe i dont know how to put them back in.....

Is there a method to insert carbs into those rubbers? .. Usually i hold the carbs and push them all together ..... and then i screw on the collars.

what do you think?

[Fizzer Thou]

If you suspect that the inlet rubbers might be leaking,spray something like WD40 around each one in turn and see if the revs pick up momentarily.

Whenever I reinstall carbs onto inlet rubbers I always spray a little WD40 onto each and the carbs slide easily into place and soon evaporates.

Check to ensure that on each air/mixture scrw that the spring,small washer and 'O' ring are in the right order.As the 'O' rings are so small,it is easy to assume that they are ok.I have known for such pieces to be slightly worn and new ones are worth the effort,especially as new unleaded petrol comprises of between 5-10% biofuel which can compromise rubber parts.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[prawny1]

When you are putting the mixture screws back together before they go in they go spring, washer then o-ring.

If the oring goes in the wrong place you wont get a good seal round the mixture screw.

Also have you balanced the carbs and checked non of the linkage springs have been left out?
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[azazelus91]

the symptom of O ring rubber seal from mixture screw is hard start or high idle / acceleration?

also what about the float needle... if that one is broken and doesnt close the valve 100% what are the symptoms?

thanks again

[prawny1]

Flooding, misfire, black smoke, hard starting, poor throttle response that worsens as the bike warms up, difficulty in finding a stable idle.

Oil level can rise with leaky float needles thanks to fuel being dumped into the engine, pull the dipstick/ filler screw and smell the oil.

the norm for these seem to be between 1.75 and 2.25 turns on the idle screws so try about 2 turns and see how it goes.
____________________
hellkat wrote:

Some people are only alive cos its against the law to kill them.

[azazelus91]

[azazelus91]

Flooding, misfire, black smoke, hard starting, poor throttle response that worsens as the bike warms up, difficulty in finding a stable idle.


I dont have any misfire . throttle response is fine at 2.5 turns and too much ( acts like i have air leak ) at 3 or 4 turns. When bike is warm 2.5 turns throttle is ok for 3 or 4 turns it goes 11 000 rpm with a small touch of throttle.

i have stable idle:

2.5 turns - 1500 rpm idle

3 turns - 3000 rpm idle

4 turns - 10 000 rpm idle


Oil level can rise with leaky float needles thanks to fuel being dumped into the engine, pull the dipstick/ filler screw and smell the oil.

I will try this .. but i haven't notice any smell. I am pulling the carbs out and in and there is so much smell of petrol is hard to notice if it smells on exhaust but i guess not.

[prawny1]

When you cleaner the carbs did you pull all the emulsifier tubes out (the part the main needle slides into) these can get gummed up and reduce the atomisation of fuel through the carb and affect the mixture all over the place.

It is also worth checking all the slide diaphragms are all lined up properly if you have the top covers off.

What you are describing sounds like an air leak more than a pilot setting issue to be honest.
____________________
hellkat wrote:

Some people are only alive cos its against the law to kill them.

[azazelus91]

[prawny1]

butterfly spindles can leak as can carb balance points (either screws or rubber sleeves over a tube) diaphagms can leak too but usually they cause hesitation and stop you reaching full revs.

Did you double check all the jets got screwed in ok, I have put carbs back on before and forgot to screw the jets in so they just dropped into the float bowl the bike flooded badly until I realised.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[azazelus91]

[stickybackbob]

Now I'm no expert on carbs so excuse me if I'm wrong here but doesn't winding the adjusters out weaken the mixture therefore giving the high idle speed and poor starting?

May be turn the adjusters to 2 turns and give that a go before pulling the carbs apart again?

As the carbs have been messed about with (on/off the bike and mixture screws played with) I would recommend getting them balanced again once you have it running as near as you can get it.

[azazelus91]

[azazelus91]

[azazelus91]

Hi guys.... it seems that one washer was missing from the mixture screw.

So we have on mixture screw --- spring --- washer --- O ring.

Do you have any idea where i can find in UK such a thing? or maybe online?

Thanks

[Pete.]

[Fizzer Thou]

[azazelus91]

[azazelus91]

Hi again guys.

Ok so i did the mixture screw 2 turns. all O rings are good. The bike works fine now on acceleration. No hesitation nothing.

But .. i still have the problem with the cold start. When it is cold and choke 100% bike starts and dies. I have to repeat this step 5 times and then it is ok.

I dont understand what the problem is.

[prawny1]

By balance point I mean where the guages are connected to,

The pilot screw can be set up to control total idle air/fuel flow or idle airflow with the fuel being unmetered.

with the first type screwing the pilot out will richen the mix as both the air flow through the idle circuit and the fuel from the slow speed jet must pass the needle, with the second type the pilot screw can only add more air to the mix the further you screw it out because the fuel flow is being directly metered by the slow speed jet.

first type goes air bleed, jet, pilot screw and is called fuel mixture screw. this type will have a separate orifice in the carb throat to control idle fuel flow and usually three smaller holes just under the butterfly that the pilot jet will flow through to transition to the main jet, adjusting the pilot screws on this type of carb only effects the idle air/fuel mix not the slow speed circuit.

second type goes air bleed, pilot screw, jet and is called idle air mixture screw. The idle and slow speed/pilot jet will share the same orifice usually. On this type of carb the pilot screws will effect the air fuel mix of both the idle and slow running circuit so if they are screwed out too far it will be like having an air leak.

It sounds like you have the second kind of carb where the screw controls air flow into the idle/ slow speed circuit which if you have them out too far will cause the bike to rev high and hang like you describe.

In this case you need to screw the pilots in to richen up the mixture and probably need to lower the idle speed via the idle/ tick over screw.

The carbs had probably been adjusted and balanced without cleaning, so when you cleaned everything the old settings became useless, you will need to rebalance the carb with gauges eventually but a good place to start is with a set of toothpick or some stiff wire (welding wire or something), with the carbs off identify which is the control carb this will be the one that has the throttle cable and the idel speed screw on it,

Next take your wire or tooth pick and adjust the idle screw so that the tooth pick is a tight sliding fit under the butterfly then match the other three butterflies to the same position by placing the toothpick/ wire in the same place you did for the first carb and adjusting the little spring loaded screws until it feels the same.

Once you have adjusted them all snap the throttle shut a few times and recheck once you have finished your carbs are now "bench balanced" often this is good enough and only minor adjustment is needed.

Once the carbs are back on screw the pilots to about 2 turns out and run the bike to set the idle speed,

you then can adjust the pilot screws, slowly turn the screws out bit by bit until the bike begins to hang when the throttle is blipped and note the settings then turn the screws in until the revs begin to dip then settle after being blipped and note the settings usually setting the screws inbetween these two point is ideal ,

Using the two numbers you can work out the how many turns out you need, for example if the bike stumbles at idle with 1.5 turns and revs hang at 2.5 turns the you set the screws in between these two which is 2 turns. if you find you still have some hesitation you can set the screws 1/8 turn at a time either way to see if it helps.

Damn it takes me ages to type a post when I started you had not replied.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[azazelus91]

[prawny1]

If your bike is running with no hesitation and the revs no longer hang then I would say they are fine as they are, have you put the air filter back in yet? as that can alter the fueling and can make a bike more difficult to start.

As for the choke issue that could be float height needs setting, when on choke do the revs change if you bounce the front end? my bike would dip revs if I bounced the bike until I reduced the float height a couple of mm (found out later Honda changed the service setting too for the same reason).

Some bikes just don't like full choke either try some different procedures when starting the bike, you shouldn't need the throttle open but I find with some bikes a little throttle on a cold engine is enough for it to catch, maybe try different amounts of choke too 1/2 choke instead of full maybe.
____________________
hellkat wrote:

Some people are only alive cos its against the law to kill them.