TOPIC:

So, I seem to have the inverse problem of a lot of folks, which makes looking for information really difficult there's about a million threads talking about issues with the bike running unless the choke is on, but very few about my problem, which is that the bike will not run with the choke ON. I would expect poor power and stalling with the choke on, especially at speed, but I would also expect the bike to be able to run with the choke applied, especially when the engine is cold and the bike is being started for the first time that day.

As it stands right now, the bike will start up with the choke applied, run for a second or so, then stumble and die. If the choke is immediately cracked after starting it, it will idle and you can feather with the choke lever to keep the idle between 1500-2000 RPM, with the lever moving down/off somewhat gradually as the bike warms up. But at any time, if the choke lever is fully applied, regardless of throttle, the bike will die pretty much immediately.

This is a stock 1980 KZ440-A1 LTD, with the stock airbox, exhaust, jets, and carbs. They're Keihin CV34 carbs, so they have a flap choke and not an enrichener.

It runs really nicely once the bike is warm, and it still starts up really easily even cold. It's just hard to keep it running when it's cold and needs the rich mixture.

That does not seem all that odd.
First, do not touch the throttle when starting.
Secondly, this time of year, full choke may not be needed, depending on where you are.
Threely, opening he choke a little at a time as the engine warms up is normal.

That being said, well, written, if the fuel level in the carbs is too high, the mixture may be too rich with the chokes closed. It is fairly easy to check using the clear tube method described in the factory shop manual.

That's normal for a properly jetted carb.

I definitely don't normally touch the throttle while starting. It's good to know this isn't an entirely unexpected behaviour.

The fuel level in the bowls (as measured with a clear tube) is about correct. I'll recheck, as the last time I did was quite a while ago and the carbs have come off the bike several times since then. I wouldn't see any reason for the fuel level to change a lot, since they have sealed rubber floats, but it certainly doesn't hurt to be doubly sure.

I do know that I generally cannot start the bike without using the choke, unless the engine is warm from having been ridden recently. My understanding is this is normal and desirable.

The stock carbs are actually 36mm.


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Nebr_Rex wrote: The stock carbs are actually 36mm.

I haven't measured them, but I do know they are stock carbs for the 440. So they must be CV36's.