lean mixture on one cylinder

Hi

My first thread here...

I have a kz650 B2 1978.

The bike runs fine, but cylinder #2 get to lean mixture, so I thought that I might try to adjust the air screw. I've understood that on my model there is only an air adjusting screw, right?

According to Kawasakis parts diagram, the number 42 adjusting screw have have two names:
SCREW,PILOT ADJUSTING and
SCREW,AIR ADJUSTING

What's the difference? In the parts diagram it says that the first one is newer and the second older.

Is this adjusting screw the right one to adjust the mixture? How do I use it? Do I turn it in to richen the mixture and out to lean it even more?

Would be happy if anynone could shed some light over this matter.

/Martin

Sure Martin, first of all I gotta say.... NICE looking bike! Don't recall what year they switched from pilot screw to air screw but the pilot screw located on the bottom of the carb controls "gas", so turning in leans out and turning out richens up. The "air" screw located on the side of the carb controls air, now it's the opposite. Turning in reduces the air which richens up and turning out allows more air which leans out the carb. Both accomplish the same thing at idle...

Thanks!

This is how my carbs look like. From your excellent explanation, the marked screw should be the air adjusting screw, right?

M

And this is the bottom om them...

Could the marked area be the gas adjustment screw, then? Couldn't see if it had a screw or not.

M

Your bike's carburetor assembly is equipped with air screws and not pilot fuel mixture screws. Turn your air mixture screws in (close them) for a richer PILOT air/fuel mixture.

Marp68, the factory adjustment is 2 +/- 1/4 turns out. How are you determining that #2 cyl is running lean?

OK, great, I'll try that. Thanks.

After buying it last year I noticed that it is a bit difficult to start smooth and nice on all cylinders. Sometimes #2 had some problems. After a few minutes all cylinders run. When riding the bike it works well. No misfiring or so.

I had a look at the sparkplugs after a ride and saw that #2 looked overheated. To little gas. The other plugs look ok. I also took it to a mecanic who said the same thing, but that I could run it anyway, since it at least got gas and run well when warm. It's an old bike he said ...

I have thought of measuring the valves, but didn't want to take anything of the engine apart this year, since it runs well. I will also run som gas system cleaner (similar to Sea Foam) to clean out the whole system.

Is there any danger with richen the mixture by adjusting the air screw to much, if the air is not the problem? I will set it within factory adjustment limit. Since a lean mixture is not good for the engine, I want to try and fix it. But since the bike runs well, when it is warm, maybe it's not really a big issue. I just like to take care of the bike ...

Before I run a newer bike, a Ducati Monster 900. It also has the classic look, so thats why i'm into these REAL classics. The Kawasaki really has a personality... I like it.

/Martin

The rain is pooring down every day, so no biking at the moment ...

I checked the air adjusting screw. It was set to about 3 turns out. Since the factory settings is 2 +/- 1/4 turns out, I now adjusted it to 1 and 3/4 turns out.

Will let you know of the results

/M

There are many posts on this very topic of mixture difference on one cylinder. I hope the Sea-foam type stuff does the trick.

Many of us have re-built and cleaned the fuel system and carbs from tank to tail to amend such problems. Seems to be a bit of an Achilles heel for the old bikes.

3 turns is quite a bit, should make a difference how you set it. How were the other screws adjusted?

Jippie!!! Snow is gone!

I went for a ride today. After warming the bike up, I tested to adjust the air screws. On #3 and #4 I noticed small changes when adjusting the srews. When I turned one of them completely in, the rpm dropped and the bike died eventually. But when doing the same to #1 and # 2, nothing happened, just a tiny change. But the engine continued to run almost perfect.

Couldn't this indicate that I have an air leak around these two? The rubber ports between the cylinders and carbs have cracks, but have been fiexed once with some sort of silicon gasket thing. Maybe there is a leak still.

It also seems that the bike starts easier, when setting the petcock to PRI before starting it. So maybe when starting the bike, not sufficient vakuum is being created.


The first time I took the bike out this season, I also had some trouble with leaking T-connection between middle carbs. But moving it around a bit and tapping the bowl seems to have done it. After a while even the malfunctioning petcock started working correctly.

I'm happy. And tomorrow is going to be nice as well, so I intend to go for a longer day ride.

Thanks for all advices!


/Martin

New carb holders can make all the difference in the world! Small cracks indicate trouble, even old ones that look good can and most likley are leaking. This is the main connection between engine and carbs, after 30 years they are done.