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It was a harbor freight one, time to got get a nice one!

My apologies I was calling the feeler gauge the shim, still new at this.

It does rev, with hard acceleration, have yet to try and redline it. If I creep up by a thousand rpms at a time, between 3500 - 4000 I will loose increasing power, and I can turn the throttle probably a quarter of a turn with no change, before it jumps up to five six and so on.

zachsnacks wrote: Update - Valves are shimmed.

Note - when doing that valves and the valve is on the downswing about to go up, the manual notes it should be a quarter turn to the timing mark, though mine was a half turn.

Still miss firing at 3500-4000.

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When anyone checks and sets valve lash on the KZ400/440.
I suggest the engine be at TDC on the compression stroke and set lash at the high side of adjustment [ .007 ].
This because of how these cams wear over time. I have indexed the profiles of these cams and they have excessively
long opening and closing ramps from .000 to .005 lobe lift. This can promote carbon buildup on the valve seats.


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Would you consider it a red flag if TDC of the valves and the timing mark of the advancer is not the same spot?

If you can get past the hesitation and get to 5000 and 6000 RPM, then the ignition is probably ok and not the source of the hesitation. The advancer is most likely fine too. When the advancer won't advance, the engine won't rev up under load no matter what.

Not sure what you mean by TDC of the valves. The valves don't really have a TDC position that is part of the valve timing procedure. TDC usually refers to the pistons.

Both pistons should be physically at their top dead center position when the advancer's T-mark line is lined up with the pointer. If not, then the advancer must be corrected to the pistons. It's hard to identify the pistons TDC directly. I use a feeler rod of some sort through the spark plug hole. Then I use a visegrip on the crank to rock the crank back and forth when the piston is at TDC. Look where the visegrip is when the piston just starts to move in either direction. Then the center point between the two positions is the crank/piston true TDC. The timing mark on the advancer is usually within 1 or 2 degrees of the real TDC, and that is usually close enough for a streetbike to run without any issues at all.

I suspect your hesitation in that midrange RPM is a jetting issue or carb condition or maybe even a vacuum leak.

zachsnacks wrote: Would you consider it a red flag if TDC of the valves and the timing mark of the advancer is not the same spot?

There is no such thing as TDC of the valves.
The KZ400/440s pistons rise and fall together.
When they are at TDC one will be on the compression stroke
and the other will be on overlap.


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Alright the only thing left is a new set of jets, which I plan to order but have not done it yet.

Video attached, you will see right at the 4000 mark it falls. I hold the throttle completely still and you see it fail, then after about 5 seconds I start to turn the throttle more, about 4 seconds of nothing, then it jumps up and kicks over four, but it sounds bloody awful.

Any guesses?

Wow, I can't believe I was able to download that video and get it to work!

That was not under load, but it did finally rev up past 4000, so the ignition is probably ok, at least functional even if not exactly right.

So it will take some carburetor investigation to find out why it doesn't rev smoother.

First thing I would check is the diaphragms to make sure they don't have pinholes. The pinholes are sometimes hidden right where the rubber meets the slide.

Yeah, the upload process was a little clunky, I wish I knew a better way. I had to open it in a new tab to make it work.

Someone suggested inspecting the needle and the needle plug.

If the diaphragms are torn, there is place called JBM industries that makes new ones. I think they might have some for the Kz440, maybe.

Usually it means breaking the plastic clamping rings to get the old ones off. The new diaphragms don't use the clamping rings.

Needle plug is not a correct term.
Which needle are you referring to?
Is it the needle and seat or the needle jet and jet needle?
The needle and seat could be dirty and leaking.
The needle jet and jet needle if stock are non adjustable.


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