Strange carb issues

Just when you think your carbs are clean.....they're not! The ONLY way to get them clean is to completely disassemble them and clean them by hand and visually inspect every passage. Many times if you don't remove them from the rack and clean the pipes between the carbs, junk can hide in the pipes and flow right back into a "clean" carb. Think of it like this, would you change oil and not the oil filter? As soon as you start the engine the oil goes into the dirty filter and picks up trash. Same theory applies here. Trust me, I had my carbs off of my 650 almost every day for the first year.

After they are really clean, make sure you check your float levels. You may also want to take apart the fuel valve and clean/rebuild/replace as needed. Trash will hide in there and flow into the carbs as soon as the fuel is turned on.

Seems like a good thought.

I'm off to get som carb cleaner today and get to it in the afternoon.

Is it possible to see if a passage is blocked and that all passages is okej after cleaning them?

Many thanks again for information, perspectives, recommendations, ideas, etc.

This helps me feel more secure both that it really is blocked passages and to start dismantling the carbs. Before I have only done everything except dismantling an engine and carbs (though I have changed the clutch on a Ducati I had before).

I'll let you know how it goes.
/M

No luck! #-o :sigh:

One thing I've discovered is that my Haynes manual does'nt cover my modell, only B1 (i've B2). So the carbs are differently constructed. My carb has combinated air/gas-mixture screws on the outside of the carbs. In this manual it looks like the pilot mixture screw are found in the float bowls.

However, I drained all carbs, then dissmantled the bridge with all carbs (quite easy), then opened the float bowl (one at the time) and removed all parts that the could be removed:
-main jet+air bleed tube
-starter jet (adjecent to main jet)
-float+float needle seat+needle+pivot pin
I also unscrewed the air/petrol-mixture screw completely (remembering the positions)
I also checked the throttle valve and needle, which work and look okej.

The float bowl and around all parts looked very clean and all removed parts were okej. All holes visible and functioning. When I sprayed carb cleaning gas in all holes, both from within the float bowl, through the air/gas-mixture screw hole on the outside and from air inlet and air/fuel outlet (towards the cylinders), the cleaner always squirted out somewhere else. So, they "seemed" okej.

One thing though, when reading about how the carb works, I understands it that when starting from cold, the petrol works its way only through the starter jet. And the choke lets more air mix itself with the petrol. The other jets etc. are only working when started and using the throttle.
-So, shouldn't there be something wrong only with the starteing process/operating parts?
-Could the parts involvded during the starting process be blocked?
-Or could there be a vacuum problem, so that no petrol is sucked further to the cylinders. I however put the tap on PRI, so the vacuum function in the tap is not operating, right? But there is the vacuum tube from the carb to the tap. Can this make something go wrong?

After my not so thourough cleaning, I put everything back again (also quite easy). Nothing happens. Petrol reaches the bowls, but not the cylinders.

Does anyone have drawing of tha Mikuni carbs on my model (Kz650, B2 - 78)?

I still don't buy that all carbs just suddenly stop working, when everything woked great before storing the bike. :iconthinking:

Unhappy Martin

According to kawasaki.com, oem carbs are same on 1977 KZ650-B1, 1978 KZ650-B2 and 1979 KZ6750-B3.

When cranking cold engine, choke should be full ON, and throttle not touched (i.e., carb slides left closed in their all the way down position).

Hoping the fuel is fresh and not stale.

Has starter fluid (ether) been sprayed into carb air intakes while attempting to start the engine?

What are fuel levels in float bowls as shown by the clear tube test?

Good Fortune!

[Click on image to enhance view.]

Mine looks more like the one with the pilot "air" screw on the outside. Maybe it's just a pilot air screw then, but on the outside.

The Haynes manual I have says it covers B1 1976 on. My carbs looks differently tha the one in the manual. I don't have the pilot mixture screw on the inside, like shown in the manual (sharp end and with a spring on it), only the pilot jet, adjacent to the main jet. And in the manual there is only a plug, where I have a pilot screw on the outside of the carb (sharp end and with a spring on it).

I was thinking that someone in the building may have changed the idle/throttle screw. It looked okej, though. Inside the carb the throttle is almost fully closed, just a tiny hole at the bottom, like almost closed. I think that's okej, or should it be fully closed or more open? Or may someone have changed the choke function? It doesn't appear so, though.

I do use the choke and no throttle. It is strange that something that worked okej last year, now suddenly not works at all. Not a single sign of fireing. And it seems that no fuel reaches tha cylinder, so either all carbs are blocked or no suction pressure is created. could there be too much air or to little to create these problems?



/M

Don't confuse internally located pilot jet (accessible only when float bowl is removed) with externally accessible pilot adjustment screw which may be side-located air screw or bottom--located mixture screw.

Good Fortune!

Here's an example of side-located pilot air screw.

[Click on image to enhance view.]

I understand that some oem KZ650 carbs have both side-located and bottom located pilot screws.

There is only one idle adjuster thumb screw that simultaneously regulates position of throttle slides on all four carbs.

Some carb designs have the idle thumb screw accessible from the top of carbs.

Other carb designs have the idle thumb screw accessible from the bottom of carbs.

Good Fortune!

Have you pulled the fuel tap off the tank and cleaned all the screens? Since you said you did not winterize last year before you put her away it could be a tankful of stuff clogging it up. Clean carbs should have a clean fuel source or problems will arise.

Marp68 wrote:

...Petrol reaches the bowls, but not the cylinders....

Marp68 wrote:

...And it seems that no fuel reaches the cylinder....

What are fuel levels in the float bowls as determined by the clear tube test?

Where fuel level is too low, the mixture is usually too lean, and there may be insufficient fuel in pilot circuit, resulting in little or no fuel mixture being sucked from the carb into the combustion chamber.

Good Fortune!

:lol: :woohoo:

It started!

I thought that it must be something that effects all carbs. Even though I don't remember changing it during the winter (why should I), I had a look at the throttle stop screw. I thought that maybe it should be more closed or open at start. I changed the throttle stop screw a bit and suddenly the engine at least fired off a little. With some help of starter gas the engine started and idled on choke. But not so fast like it normally do. I had to use the throttle. So I changed the throttle stop screw a bit more so the choke could do its work. Like it should do. After a few minutes, I could lower the choke and let the engine idle as normal.

I've never experienced these problems before. I don't know if some asshole in my building that knows how it works changed it as some sort of practical joke....

Anyway, big thanks to you all for being a great support. One feels a bit lonely in the garage without anyone to ask or discuss it with.

Today it was sunny weather, so I've been out for a ride in the afternoon. Felt great!

Have a nice bike season

/Martin

Marp68 wrote:

...seems that no fuel reaches the cylinder....

Perhaps a clogged enrichener (choke) circuit.

[Click to enhance view.]

Good Fortune!

[Click on image to enhance view.]