You didn't happen to accidentally hook up the fuel tank vent to a vacuum port on the carbs?

 

Well no, I don't think so. The vent is on the back of the tank, just under the seat.
Then on my bike theres's a stiff blue hose running right up to the smaller port on the petcock, the bigger one is the fuel.

 

Pull the spark plugs after running and see which ones are wet with fuel.

 

I'm assuming all of them are. What information exactly would you hope to gain from this?

 

I'm checking out of this thread. Good luck.

 

DerEnstafferrr, welcome to our forums.

Some basic advice for you as a new member, if I may.

As a general rule, assumptions made during troubleshooting can often lead to to a much longer time to arrive at a solution.

We are all volunteers on this site and we take time out of our day to help others. So it's probably not a good idea to question the advice given because this forces that person to take even more time out of his day to explain his advice.

Just sayin'.

 

Oh I'm sorry, I wasn't trying to question the advice, i was just trying to get what that would do, as I'm new to vacuum operated carbs/japanese bikes.
Did not mean any harm!

 

Understood. The reason for checking the spark plugs is to find which cylinders are over fueled, it's a diagnostic method to narrow down the problem.

 

That float level setting seem ludicrously high to me though I have no specific knowledge of this bike. Have you tried confirming that the figures in the manual are correct?

It would not be the first time that the manufacturers get the data wrong, it does seem to be a general pastime for Kawasaki / Keihin more than the other manufacturers.

 

How are you checking and setting the float level?

 

How I do it.

 

What some people don't know about this method is that you have to be very careful not to lower the graduated cylinder and then raise it. Doing this will give you the wrong reading.

When using this method I got so frustrated with trapped air bubbles in the hose so I 3D printed a clear float bowl cover just for use while I set the float height.

An added benefit of using the transparent cover is that you can watch the bowl filling with gasoline and this allowed me to verify that the inflow rate was the same on all carbs. In my case one carb was much slower at the refill. Once I removed the blockage, the flow was normal.

There was a time when you could buy transparent float bowls for most any bike. They were made of Lexan plastic I think and were intended as a permanent install.

 

Hmm, whenever I try that I end up with a sieve and a not too transparent one at that.

Presumably this figure is given by Kiehin. As the carbs on this model are not vertical ( hard to be sure, I have only googled images of the bike and most of the images have fairings) will Kawasaki not have altered the level specs to cope with a sloping carb?

 

A leaky 3D print can be due to filament material, application temperatures, wall thickness and density of print. You can also seal your print afterwards with any number of sealants.

The factory service manual (FSM) should advise on slope, but in any case measuring in the middle of the carb will average out the slope of fuel in the bowl. But what is vital is what is the reference? Outside visible seam or gasket surface of upper part of carb?

A key question: Does the OP have the FSM for his bike?

 

Hi again,
Thanks for all the replies.
I set the fuel level the same way C-130 does, fully upright with the carbs in the vice. The repair manual calls for .5mm below - 1.5mm above the seam; mine are set at exactly the seam, so technically a little on the low side. It also says they´re supposed to be fully upright during this procedure.

I now also tested the petcock by pulling a vacuum with a syringe on the vacuum port, and there is only fuel coming out where there´s supposed to, the syringe is completely dry. Kinda hoped that was it, but no.

I did not yet check with plugs are wet.

I´m doubting the jet kit I bought is right. The pilot jets are now size 40, the main jets on 1 and 4 are 128 and 2 and 3 are 130. The needles are shimmed up 1mm.
There are pod filters on the carbs and there´s a 4in1 exhaust on the bike, kinda high flow just going off of the sound. Maybe the jets are just too big?

In addition, I´m not too sure about the needles either. They were in the bike, which was completely OEM except for the exhaust, though I don´t know if the needles are OEM as well. I have attached a picture of one of them, maybe somebody knows what they´re supposed to look like.
IF they´re not OEM, which would make sense, that would explain why the problem is much much worse when going full throttle.

Is there someone with a similar setup just to compare jet sizes?


Also, I do not know if the problem existed with the original carb and airbox setup. When I got the bike, it did not run and the carbs were not attached properly. Maybe someone before me had the same problem and just didn´t bother to put everything back together, who knows.

 

I set the fuel level the same way C-130 does, fully upright with the carbs in the vice. The repair manual calls for .5mm below - 1.5mm above the seam; mine are set at exactly the seam, so technically a little on the low side. It also says they´re supposed to be fully upright during this procedure.

Which repair manual?

You need to confirm that is the correct figure really.

 

I got round the problem by vacuum forming them from Tesco's chocolate cornflake packaging.
My 3d printers are very old, significantly more than ten years, as the technology goes. It works for me so I have never bothered updating.

I am not sure centre (front - back) would solve the problem. I would have thought if the carb is leaning forward at the top then the reference should be the front of the float chamber. It does of course, depend on the internal design of the carb. It is not a trivial thing to try and sort without input from the designers.

 

This is the manual I´m using, looks original Kawasaki to me.

 

OK. What I would do:

Try to find another source for that float level data.
Plugs out and are any significantly different from the others. If so then concentrate on that carb for now.

Get 2 or 3 metres of clear pipe and connect it to each carb in turn. Tie the end of the pipe somewhere high up so it is exerting more pressure on the carb float valve than is normal. Engine not running, throttle full open.
Fill the pipe with petrol and watch for the level going down.

That's the start.

Presumably the petrol tap has a prime position on it. If so then disconnect the vacuum pipe from the tap and block the pipe to stop the carb sucking air. Use only the prime position. That removes one of the possible systems from the equation. There is no point trying to diagnose the problem when it could be the petrol tap or it could be the carb. Take it for a ride. If it still does it then probably the petrol tap internals are OK. If it does not do it then maybe the petrol tap diaphragm is at fault, leaking under a lot of suction.

It really is just a matter of removing elements and investigating, trying to identify where the problem is.

 

You're fine with the float height, if it were way off you'll know at idle with fuel coming out the air jets. People get really anal about float height measurement techniques and such.

128 & 130 main jets sounds big to me for a 750 and you don't need to have richer jets in the middle cylinders that's a air cooled big motor approach.
I'm running 132 on a ZG1000 with GPz carbs and cams. Basically a larger version of your engine.

https://www.kawasakimotorcycle.org/threads/video-zg1000-to-ninja-mod-finally-finished-and-tuned

 

DerEnstaff, I have the same bike, '87 GPX 750R so let me give you some information that may help you.
The shop manual I have says: float height 17mm, main jet 112, Jet needle N531. Your conversion to 'pod' filters etc is the cause of your problems. I had tried that some years ago and it was a serious failure, would not rev over 3000rpm. Switched every thing back to original and all was well. I admit they are a fussy bike but well worth the fun riding them when they function correctly. Too bad you ruined your carbs with the aftermarket jet kit.

'I´m doubting the jet kit I bought is right. The pilot jets are now size 40, the main jets on 1 and 4 are 128 and 2 and 3 are 130. The needles are shimmed up 1mm.' Go back to original air box and rubbers, and no shim under the needle. Also, the fuel in the oil is most likely from leaking carb float valves, clean them up so they don't leak. Those Keihin CVK34 carbs will not tolerate pod filters because the excess air flow shifts the venturi point in the carb throat. Ask me how I know this?

 

I run CVK36 and it took some tuning and jets not included with the Dynojet kit, it runs like a scalded ape with pod filters and slip-ons. Heard all that before when people give up tuning.

 

Your experience differs from mine. Was just trying to help that fellow out of his jam. Its a highly tunned bike right from the factory, she puts out over 100hp for a '87 750, with 16 valves in the head. Most comfortable bike I've ever ridden btw. I have Yoshimura 4 into 1 pipes on the left side and still able to retain the center stand, the sound is wonderful. What else can I say, best bike I've ever had the pleasure to own and ride, and I've had quite a few bikes in my day. I should add that I will never buy a modern bike if it doesn't have fuel injection!

 

I was thinking about my reply while riding my other bike. I was a bit harsh, apology extended.
It's a compromise to go full pods and jet kit, is it worth the trouble to gain 10 hp on the top end? Probably not in most instances. My Kawasaki is more of a project to see what could be wrung out of a formerly mild Concours than daily rider. Also, you ruin the resale value modifying a bike becoming collectable like a GPX750R.
That said it can be rejetted to pod filters there's no mechanical design feature stopping it.

 

Thanks for the reply. You are correct, with enough effort and thought the carbs can be retunned for pods. Its alot of fuss and bother playing with jets, rising the needle, trial runs, etc. Maybe the OP can do it, those rubber carb boots for that model bike are tough to find nowadays, pod filters sure 'appear' to be a quick fix. And of coarse resale value of a semi-classic bike. I wouldn't buy an older bike like that if someone chucked the air box for pods, that's just me though.

 

Nice bike, don't see those on the road anymore. Next year I'm skipping the Indy 500 for the vintage motorcycle race and museum at Barber.

Barber Vintage Festival | Barber Vintage Motorsports Museum

www.barbermuseum.org

 

Since there was a call on this thread for float height/fuel level data from sources other than the FSM, I have confirmed from two different reputable sources that the correct fuel service level measured from the bottom edge of the carb body is:

-0.5 Plus or Minus 1.0 (all data in mm)
So, the highest spec is 0.5 above the edge
And the lowest spec is 1.5mm below the edge

On another note, I also have all the specs for the carb jets in OEM configuration if needed.

 

Measure float height by tilting the carb to touch the tang on the carb needle valve rod (float valve needle), Bottom edge of carb body to float top: 17mm. Or as you prefer 'service fuel level' from bottom edge of carb body: standard 0.5mm below to 1.5mm above (using a fuel level gauge). Please note that not everyone has a fuel level gauge. Need pictures?, I can take a photo of where/how the measurements are to be taken. Doesn't really solve the OP's issues caused by the oversized and mixed jets, jacked up needles, and way too much air because of the pod filters. A good first step though adjusting the float height so the float valves actually close. Just might stop fuel leaking into the crankcase or overflowing. Standard main jet size is #112 for the Keihin, CVK34 carburetor on the GPX 750R engine in 1987. That should help.

 

Or as you prefer 'service fuel level' from bottom edge of carb body: standard 0.5mm below to 1.5mm above (using a fuel level gauge)...

Totally agree that there is far more going on here than just float heights. But for the record you have done your fuel service level math incorrectly. The tolerance is plus or minus 1.0 mm from the ideal level of -0.5. Don't forget your math rules of how to add NEGATIVE numbers.

-0.5mm plus +1.0 mm = +0.5mm for highest fuel level

and

-0.5mm plus -1.0mm = -1.5mm for lowest fuel level

 

So what I´m hearing is the jet kit I bought is probably garbage. Kinda thought so. Does anyone know a good jet kit with a few different sizes for trial and error?
The pod filters were never meant for more horsepower or anything, it´s just that the airbox is a leaky piece of sh.....

Also: Does anyone have any specs on the coolant temp sensor? As I said, the gauge never even reaches the "barely warm" mark when riding. While the ridiculous amount of fuel is obviously part of the problem, I don´t think it´s the whole problem. What resistance should the temp sensor show when the bikes is warm?

 

DerEnsafferrr, As I mentioned, I have the same bike so I know a bit about them. Your best course of action to get the bike running properly is to put it back to factory condition as best you can. Repair the air boxes, there are two sections to it, the big section that connects to the carb rubber boots and the back section under the seat where there is an air filter also. Make sure they fit together tightly. Get new carb rubbers if yours are bad. Put the carb jets back to factory specs, ultrasonic clean the carbs too. Make sure the carbs are in perfect condition.No air leaks. As for the temp sensor, before you buy a new one test the old one, could be the sensor or the guage. Those bikes get pretty hot when ideling, and the cooling fan comes on only at high temp, most people put a switch to have manual fan control in case you are stuck in traffic. And finally, learn to love your bike it will serve you well with some TLC on your part.

 

I agree with Ohgeewiz,

Your best and fastest way to get your bike running right is to go back to the stock airbox and stock jetting.

 

I have to agree with getting it back to standard but even with the most oversize jets in the world I cannot see a visibly dropping fuel gauge being fixed by jets.

Having said that, for sure, 100% your starting point to sorting it is to get it back to standard first.

 

I don't believe the oversized jets are the cause for excessive fuel in the crankcase. I suspect the carb float valves are not sealing. By what other method does that much fuel get into the crankcase? Fuel must be running out the carbs down through the intake valves, into the cylinders, past the rings and into the crankcase. Notice the angle the carbs are mounted at, poor float valves let fuel just overflow into the intakes.