TOPIC:

Hi KZ guru's.
I have a 1981 KZ440 C1(?) that has been in the garage for a few years. Been working on it off and on over that time, but after an extended hiatus, I am now spending more time on it.

When I got it, it was completely in parts and the parts were unlabeled, but hey, we all like a challenge right?

So at this point in time, I have a problem with the carburetors.

Just over a year ago, I sent them off to a local Kawasaki repair shop to have them cleaned up / inspected. They needed new diaphragms, but it seems no cleaning was done. The shop, strangely, wouldn't fit aftermarket diaphragms because of the risk of tearing them during installation, so I took the risk and I replaced them myself. No rips and compressed air into the carb's shows the diaphragms lifting the sliders as expected.

The carbs were in one piece when I got the bike, so had presumed that all the internal components were there.

After finally rectifying some electrical issues, I turned the bike over but ended up taking the carbs off again because fuel was just squirting out the overflow's. A quick tear down of the bowls and an inspection showed me that the float needles were gunked up, so a good clean and polish later, carbs back on the bike and no more gas coming out the overflow. Cool! However, also no fuel to the engine. But this, I think, was a pre-existing condition.

• Fuel is getting to the carbs so I don't think the petcock is faulty.
• The engine fires up OK if I squirt CRC engine start directly into the carbs, so nothing wrong with the spark from the plugs.
• The spark plugs are not wet and there is no smell of fuel in the cylinders.
• Battery is new.

So, carbs back off again, and it was while I was stripping them down that I noticed one of the needle jets was missing from one of the carbs.
These just don't fall out right? Ref part: www.partzilla.com/product/kawasaki/16017-1059



I'm assuming it is an important part as I think they are there to ensure that the correct amount of fuel is released into the body when the throttle is twisted?

Anyhoo, my other question is (while waiting for a new needle jet to arrive), is:
Would this missing component prevent fuel from getting through the carbs to the engine? In my mind, and not necessarily logically speaking , I would again assume that with no needle jet, the fuel flow would be unrestricted.

PS, I started this low-on-detail, nondescript blog when I started the bike to keep the old man up to date on progress of the rebuild.
stuconzblog.wordpress.com

I think the answer to your question is no. When starting the engine there isn't enough air pressure differential (between the carb throat and the bowl) to draw fuel up the main jet. The throttle needs to be opened up to about one quarter before the jet needle/needle jet becomes the main fuel control.

Your starting problem is likely due to a blockage in the choke circuit or in the pilot circuit.

Thanks for your advice. Will strip the carbs again this weekend and give them a real good soaking and clean.

After you're done cleaning the carbs, take a bristle from a nylon (not steel) brush and poke it through the small jet holes to ensure they're open.

The small holes are the most easily blocked and the hardest to see. A nylon bristle will allow you to remove crud but won't scratch or otherwise damage the brass.

Good luck!

My advise typically falls on deaf ears but in my experience the only way to properly clean a set of carbs is full disassembly and soaking the hard parts in carb dip. That includes unganging them, removing the pilot screws, pilot jets, bleed pipes, etc. Don't dip anything with rubber or plastic on it of course. Once everything is clean get all new O-rings and maybe new float needles and put them back together again. The fuel Tee O-rings are the ones that are typically the most deteriorated and the only way to replace them is after unganging. Use loctite on the choke plate butterfly screws and consider making a tool to upset the end of the screw and flare it out just like the factory tool for the same work. If you need more info PM me. I've rebuilt lots of sets of KZ750 Keihin's which are basically same, just twice as many.

I agree with Nessism on how to clean carbs. I would add that you should blow some compressed air into each orifice to see if it's clear before reassembling. If you don't have a compressor you can buy a can of compressed air at any electronics counter.

I've pulled the carbs and stripped them completely (sans the idle jets) and everything is spotlessly clean now. I was able to source a new replacement needle jet as well (ironically from the same shop I mentioned earlier...). The carbs are all back together, back on the bike, and the bowls are filling up with gas OK, but engine still not firing unless I squirt engine-start into the carbs.

I have not replaced any jet needles or o-rings at this stage. The problem with living down-under, is parts can take weeks to arrive, and rather than farting around with one part at a time, I'm making a big ol' shopping list and will try to do most of it at once. Or at least in batches...

A couple of other things.
I did refer to this earlier, but again, the needle jets just fall out when you turn the carbs upside down. Should they do that?

And, when I was testing the diaphragm / vacuum piston was functioning OK with compressed air, the original needle jet unseated from the carb body when the vacuum piston / jet needle went up, but didn't seat properly when they came down again. The new needle jet did not do that...(I wonder if the jet needle itself is bent?) It looked OK on inspection. I might just go ahead and switch them around and see if it does it with the other needle...

Here's a vid of the issue.


I swapped the needle jets around, still the same issue in the left carburettor.
Swapped the jet needles around and still the same issue in the left carburettor.
So I think I can rule out those two components as being the cause.

Any other suggestions? (otherwise I might have to wave the white flag and send it off to a pro... )

When you removed the pilot jets and bleed pipes did you use a wire through them to make sure the orifice is open? Hold them up to a light to check for a clear passage? Before dipping did you remove the pilot screws to assure the cleaning sauce makes it through the passages? How many turns open are the pilot screws?

First the slide must come down on it's own. You may have it installed wrong making it bind. I'd try turning the diaphragm slightly until it does. It should go in only one way. After you get it to drop on it's own do the thumb test by raising the slide putting your thumb over the large vent seeing if the slide drops fast or slow. If fast you have a leak. With one slide stuck you will have a rich condition flooding that cylinder. With those carbs the starting circuit is the main jet. With the butterflies closed air/fuel is drawn through the main circuit causing a "Choke" effect. With the slides raised you are drowning the engine and it can't fire.
Steve

The idle circuit is still clogged. Clean the carburetor.

SWest wrote: First the slide must come down on it's own. You may have it installed wrong making it bind. I'd try turning the diaphragm slightly until it does. It should go in only one way. After you get it to drop on it's own do the thumb test by raising the slide putting your thumb over the large vent seeing if the slide drops fast or slow. If fast you have a leak. With one slide stuck you will have a rich condition flooding that cylinder. With those carbs the starting circuit is the main jet. With the butterflies closed air/fuel is drawn through the main circuit causing a "Choke" effect. With the slides raised you are drowning the engine and it can't fire.
Steve

CV carb slides get falsely blamed for a lot of ills. They rarely cause issues unless the diaphragm's are torn. Visually inspect the slides and if no tears install them. Once installed lift them with a finger and release. They should move down with a damped motion and then thunk closed. If they do you are done. Don't spend a second longer worrying about them.