Runs perfect when warm, but cold starts require a lot of cranking

Hello all, I ride a 1982 KZ440. The bike is darn near close to stock, including stock airbox, carbs and automatic vacuum fuel petcock. The bike is tuned pretty well and I have no big issues with how it runs. However, when I am cold starting (ambient temp ~around 60 degrees for example) it always turns the engine over for longer than I think it should before firing. After it fires up I feather the choke to get a comfortable fast idle going, take my time putting my gear on, do a quick inspection, and hit the road with the choke off--works every time.

Attaching a YouTube video below... let me know if you think it turns over for longer than usual, and how to fix this problem to fire up with as few cranks as possible from cold.

Video

Sounds and looks like your carburetor bowls are empty from a cold start. When you start cranking the motor the vacuum line begins to fill bowls up. To confirm this is the issue unplug the gas line and see if the gas flow freely when the petcock is set to primary. I am not familiar with your bike setup. Just make sure the gas flows freely from the gas tank. Its better to remove the gas tank from the bike. If the gas flows freely, then your carb will need to be clean most likely.

Its old because when you park the bike after riding there is still gas in the bowls. It shouldn't be disappearing.

How long since the last time it was started?
Have you tried putting the fuel selector switch on prime first?

ThatGPzGuy wrote: Have you tried putting the fuel selector switch on prime first?

+1

I have no experience with vacuum controlled pet cocks but I think It needs to be on prime for cold starts

The only time PRI is needed is when the carbs have been drained or when the bike has been unridden long enough for the fuel to evaporate from the carb bowls.

When the engine has been running and then shut off, the carb bowls should be full, or nearly so. As long as the bike does not sit unstarted for a bunch of weeks, or a few days in the hot desert sun, there will be plenty of fuel in the bowls for starting. As soon as the engine starts, the intake vacuum will open the petcock and fill the carbs.
The Prime position can also be used to insure the bowls are full when measuring fuel level in each carburetor.

When the engine idling and you switch on the choke, what happens? Instant kill the engine?

Might not be fuel tap related at all. If the seals in the choke circuit are old and shrunken it will have difficulty sucking in sufficient fuel to enrichen properly for cold start. Continual engine cranking will slowly build the amount of fuel in the chamber until its rich enough to fire.
I know bugger all about cv carbs but if the enricher circuit is the same as vm carbs it would show the symptoms described by astrosail.

Warren3200gt wrote: Might not be fuel tap related at all. {/quote]
Yes, but he should try the easiest simplest solutions first. I suspect the enricher circuit as well... but I know mine will take a while to start if it has been a few weeks or months since I started it last. If that is the case I usually try to prime for a minute and then hit the starter.

But if its hard to start from cold after only a day or two of standing the float bowls will still be pretty much full. They wont have had time to empty from evoporation unless you live in death valley. Thats why I doubt the tap.
If the seals are worn or shrunken in the enricher circuit it will allow air to get sucked in along with the fuel and thus not providing an enrichened mixture with the consequential hard start symptoms.
One of my 650's had this issue even though the seals were all new. Finally tracked it down to the new o ring were not thick enough cross section so were not sealing adequately. Replaced with thicker ones and even after standing for a week it'll fire straight up. Admittedy with a gravity tap.

Warren3200gt wrote: But if its hard to start from cold after only a day or two of standing the float bowls will still be pretty much full.

I agree completely. If this was a daily thing I would be looking hard at the enricher circuit.

Hello I had this problem on my kz bike with bs34 carbs it has no overflow so what caused these hard starts was the the petcock was leaking and was flooding the bike which caused the hard starts. Maybe double check that your petcock isn't leaking and not flooding the bike I don't know what carbs you have and if it has overflow protection

While the bike on the center stand check your float levels with a clear tube when your engine is cold before your start the bike.
After the bike is started shut off and check the level again. Have a fire extinguisher nearby.
Also, pull your plugs before you start it to see if you're flooded like Kz700a1user said.