81 kawasaki KZ 750 help

[thespirit]

Carb boots don't appear to be a problem.

I dumped a few shots of carb cleaner into the gas tank this morning and after a quick jaunt on the highway to work, things are getting better.

After sitting all day in the parking lot, it started with a closed choke and I only had to play with the throttle for maybe a minute before it was idling fine by itself and not threatening to stall out. +1

Checked the pipes this morning and when I left work, and all four are getting burning hot right away, so all 4 cylinders appear to be firing.

It still will not accelerate past 110kmph which bothers me. This bike is rated for 195.

yesterday I stalled out and had to switch to reserve after only riding 90kms, I'm at 70 now so we'll see how that goes.

That's great that things are working better! Seafoam works wonders, you may want to consider trying some of that. There are a few ways to use it, but the easiest is to dump 1/4 to 1/2 of the bottle into a full gas tank. Use about an ounce per gallon of gas.

Not being able to get up past 110kmph may just mean that your main jets are plugged.

You will run on you pilot circuit to about 1/4 throttle, and from 1/4 and up you will be running based on the position of the needle jet. At a little less than full throttle to wide open throttle, you will be using the main jets.

You might be getting the pilot circuits cleaned out, but the main jet circuit may be still gummed up. Your best bet is to open them up and clean then all out good. Using spray cleaner directed through the circuits and then following up with an air compressor and blowing into those circuits to clear them out is good enough. Sometimes you have to do this twice just to get everything.

[telefunkin]

That's great that things are working better! Seafoam works wonders, you may want to consider trying some of that. There are a few ways to use it, but the easiest is to dump 1/4 to 1/2 of the bottle into a full gas tank. Use about an ounce per gallon of gas.

Not being able to get up past 110kmph may just mean that your main jets are plugged.

You will run on you pilot circuit to about 1/4 throttle, and from 1/4 and up you will be running based on the position of the needle jet. At a little less than full throttle to wide open throttle, you will be using the main jets.

You might be getting the pilot circuits cleaned out, but the main jet circuit may be still gummed up. Your best bet is to open them up and clean then all out good. Using spray cleaner directed through the circuits and then following up with an air compressor and blowing into those circuits to clear them out is good enough. Sometimes you have to do this twice just to get everything.

Sounds like that is exactly whats going on in regards to the throttle. Any thoughts on why it might be burning so much gas? I only got about 22 mile per gallon out of the last tank.

[thespirit]

Not 100% sure why it would use so much, it definitely shouldn't be. However, that question could be better addressed once everything is working better. It's possible that instead of it not getting enough gas, it's getting too much, causing it not to perform well.

If it were me, I would be taking the carbs off and going through them as best as I could. Check the float heights and the float needles and seats. Make sure everything is good and clean.

If you get them apart and they look like they are really dirty, you can try a product called Chem Dip, but just be careful with it and DO NOT GET ANY OF THE RUBBER PARTS IN THE CHEM DIP. It will eat rubber for breakfast. I only recommend using this stuff if you can take the carbs completely apart and get any and all rubber out of them.

Otherwise, a few cans of spray carb cleaner will do fine followed up with some air.

If you know the model of the carbs, I can get you a parts diagram so you know how they come apart and go back together. If you don't know the model, I can find out for you.

[telefunkin]

Thanks for all the advice, I think I'm going to tackle the carbs over the weekend.

I have the clymer repair manual arriving today or tomorrow, it should have a diagram. I may get back to you if it doesn't.

Thanks again.

[beardking]

If you get them apart and they look like they are really dirty, you can try a product called Chem Dip, but just be careful with it and DO NOT GET ANY OF THE RUBBER PARTS IN THE CHEM DIP. It will eat rubber for breakfast.

Sorry I'm not going to be any help on this question, but this part brought up my own question. Can the plastic parts of the float be dipped in Chem Dip? I'm not talking about the floats that are all plastic, I'm talking about the floats that are stamped steel with the floaty parts being made of plastic. I have a set of carbs that the stamped steel parts of the floats are NASTY, to the point of causing their movement to be very bad.

[thespirit]

Sorry I'm not going to be any help on this question, but this part brought up my own question. Can the plastic parts of the float be dipped in Chem Dip? I'm not talking about the floats that are all plastic, I'm talking about the floats that are stamped steel with the floaty parts being made of plastic. I have a set of carbs that the stamped steel parts of the floats are NASTY, to the point of causing their movement to be very bad.

Well, I put my plastic floats in it and they came out ok. I'm not sure how corrosive that stuff is towards plastic... I guess to be safe, you can just use standard carb cleaner on them and a brush to get it all off. You could also rig up some sort of holder to just hold the metal part of the float in the chem dip to clean that off. Then clean the floats up with the chem dip.

[telefunkin]

My petcock does not have an off position, do I need to drain the tank before removing the carb? There's no mention of this anywhere in the manual.

[thespirit]

It is probably vacuum operated. There should be 3 positions, On, Pri, and Res. On is normal operation, which requires a vacuum in order for fuel to come out of the tank. Pri is prime and will allow fuel to freely flow without a vacuum, and Res is your reserve tank. If you put your petcock to the On position, you should be able to disconnect the fuel lines without gas draining out of the tank. A bit will dribble out when you first disconnect it, but it shouldn't be flowing out of the tank.

[telefunkin]

Got the carbs off and cleaned today, also had to replace one of the plugs, overall it's running pretty good.

Starts with no trouble, idles good and not one backfire. I took it out on the highway and the pickup is much better in the higher gears. I't's now topping out at 120kph, instead of 110kph. I never drive faster than that, so that'll be ok. However, it should be going much higher than this, if anyone has any thoughts on a possible cause, please speak up. If it helps, I did notice that at full throttle it only pushes 110kph, when i drop it back slightly, I get up to 120kph.

Also, it doesn't seem to be burning nearly as much fuel as it was. After topping off the tank, I put about 50kms on it. I can still see the fuel when I look in the tank, so I might have burned 1/4 of it. Big improvement there.

[BuzZz]

You still have fuel delivery problems.

Backing off the throttle and gaining power is a sign that the air/fuel mixture is off at full throttle. It's probably getting too much air for the amount of fuel it can deliver, so cutting the amount of air by closing the throttle brings the mixture closer to where it oughta be.

It is possible it is just pouring fuel at full throttle, so backing off limits that and also brings the mixture back closer to normal. But your economy is better, so I am guessing it's too lean.

Re-clean your jets, and make sure the needle clips are in the right groove, it could be something as simple as that leaning you out.

110 at full throttle may be acceptable to you, but it ain't right. And you will get even better economy if you don't have to hold the throttle wide open at all times, eh.