Kz1100 will not start despite all signs normal

I acquired an under-10k-miles 1984 Kz1100 (LTD version).

It has spark, the starter works fine, the bike looks brand new.
But it would not start. I loosened the float bowl drain screws and found no gas flowing from the tank to the carbs. So I pulled the carbs -- all four float valves were stuck closed. I removed all the removables -- pilot jet, main jet, float valve from each carb and cleaned them thoroughly and made sure they were clear.

I then used carb cleaner and verified the pilot and main jet passageways inside the carbs were clear -- sprayed carb cleaner in the pilot jet, it came out the other end; same with the main jet.

It's important to note here that I did *not* soak the carb bodies overnight in Berryman's Carb Cleaner.

That being said, I have owned several bikes that, *even if the pilot jet* is completely blocked, you can get the engine running with the choke on.

I put the carbs back together and on the bike.

I verified that now, indeed, fresh gas is getting to the float bowls -- I loosened the float bowl drain screws and presto, fresh gas is flowing fine.

The bike still will not start even with the choke on!

So I got a can of spray starter fluid. Bike starts right up then dies.

So why won't the engine start with the choke fully on?

Have you done a compression test? Have you replaced the air filter? Does air come out of the exhaust (squirrels may have been hiding nuts in there for 20 years...). Are the rubber carb holders all cracked and dry rotted? When you had the carbs apart, did you confirm that the jet and needle numbers matched the stock setup?

Pic of the bike? Have you adjusted the valves? Sitting?
Steve

jackleberry wrote: Have you done a compression test? Have you replaced the air filter? Does air come out of the exhaust (squirrels may have been hiding nuts in there for 20 years...). Are the rubber carb holders all cracked and dry rotted? When you had the carbs apart, did you confirm that the jet and needle numbers matched the stock setup?

Actually, the engine once started with starter fluid sounds fine. No oil out the exhaust, but with under 10k miles and being the garage queen that it is (I bought it from the original owner, he kept it indoors), I wasn't surprised about the motor sounding fine, when it started.

No valve adjustments done, bone stock bike.

Here are some photos:





I pulled the spark plugs to smell for any gas, check for fouling. No gas at all, Despite having the choke on, and then having the choke off but throttle wide open, the cylinders are not getting gas.

I thought "hey, maybe the idle's out of adjustment" but it would still start with the choke on, wouldn't it.

I'm kinda wondering if the particular carbs on this model have some type of quirk that would explain why not even having the choke on will get it to suck gas out of the carbs.

Is it possible that the (vacuum operated?) fuel petcock may need to be rebuilt or replaced?

daveo wrote: Is it possible that the (vacuum operated?) fuel petcock may need to be rebuilt or replaced?

I considered it. If for example, the petcock diaphragm wasn't allowing fuel to flow out of the bottom of the gas tank, that would explain everything. But I checked it by doing the following:

1) upon finding the engine wouldn't start, I checked for spark: no problem, sparking fine.
2) loosen the carb bowl drain plugs one at a time -- is the fresh gas I put in the gas tank making it into the carb float bowls? NO. None of the float bowls were getting fresh gas.
3) I got lucky with this bike's petcock -- it has a 'Prime' selector on the petcock! I love those. Put it on prime, is gas coming out of the petcock? Yes.
4) I then using the red straw on the can filled up the gas supply hose from the tank to the carbs with carb cleaner, 'maybe the float valves just need some carb cleaner coaxing'. Check the float bowls a little while later, "any carb cleaner coming out of the float bowl drain plugs?" Nope. And the gas supply line was still pretty full of carb cleaner.

With the 'Prime' setting selected on the petcock, the cool thing is you can at least temporary take the petcock diaphragm out of the equation.
I left the petcock in 'Prime' and the bike would not start, and the float bowls were not getting fresh gas.

I pretty much knew some sort of blockage was in the gas supply line to the carbs so I pulled 'em. Sure enough, all 4 float valves were stuck.

After the carb clean and re-install, I left the petcock in the "Prime" position to take the petcock's diaphragm out of the equation.

And that's where I'm at, carb float bowls now successfully getting fresh gas, but NONE reaches the cylinder, even with the choke on.

And there's no air leak from the rubber intake manifolds, they're not cracked/dryed out/broken, the bike's always been in a garage, and this is California so our garages don't get cold. The rubber bits on the bike are in near-new condition, including the seat.

If you haven't already done so, you may want to perform a "clear tube" test to see if the fuel in the carbs is rising to the correct level. Ed

650ed wrote: If you haven't already done so, you may want to perform a "clear tube" test to see if the fuel in the carbs is rising to the correct level. Ed

Good suggestion, I have a tool I bought years ago with tube + fittings to screw into the drain outlet, haven't thought to use it yet.

My reason for not using it yet is twofold:
1) when I pulled the carbs to clean them, I didn't change the float-height adjustment tab on any of the floats. Since the bike is all stock and very low miles, I made an assumption the float height is unchanged from its original condition. While not conclusive, it's a safe bet that the float height's okay.

2) AND -- I may be leaning too hard on my expectation of what the choke should do, but unless the float height and fuel level are WAY low, which I sincerely doubt, it's been my belief that the choke cuts off so much intake air that the engine intake vacuum has no other avenue but to pull fuel out of the bowl.

So with this in mind -- assuming the float level/fuel height are okay -- and I'd wager 99 to 1 that they are -- is there some condition in the carb, like something else clogged up, that would stop the fuel being sucked out by engine vacuum, while the choke is on cutting off airflow from the airbox?

It just doesn't make sense to me how, with the choke on thus shutting off airflow from the air filter that the engine vacuum wouldn't suck the gas right out of the bowl.

Thus my weakness here is this: on this particular carb type, a CV type of carb that may have some peculiarity I'm unaware of on this model -- I guess I don't get how this model of carb flows gas into the cylinder when the choke is on.

Because it's my belief that it *should* and it clearly is not.

I'm gonna bust out my fuel level gauge tomorrow. My guess right now is, on this model carb, even with the choke full on the bike will not start if X is a present condition, but I don't know what X is, yet.

My most recent experience with completely clogged pilot and main jets was a Kawasaki 750 Vulcan. This model also has CV carbs. Pull on the choke, bike would start fine. Open the throttle to 3/4+ to bring on the main jets, sputtering.
Leave the bike idling with the choke on. Then turn the choke off. Engine dies. I pulled the carbs -- pilots and mains were blocked.

But the damn Vulcan at least would start up with the choke on.

newOld_kz1000 wrote:

650ed wrote: If you haven't already done so, you may want to perform a "clear tube" test to see if the fuel in the carbs is rising to the correct level. Ed

Good suggestion, I have a tool I bought years ago with tube + fittings to screw into the drain outlet, haven't thought to use it yet.

My reason for not using it yet is twofold:
1) when I pulled the carbs to clean them, I didn't change the float-height adjustment tab on any of the floats. Since the bike is all stock and very low miles, I made an assumption the float height is unchanged from its original condition. While not conclusive, it's a safe bet that the float height's okay.

2) AND -- I may be leaning to hard on my expectation of what the choke should do, but unless the float height and fuel level are WAY low, which I sincerely doubt, it's been my belief that the choke cuts off so much intake air that the engine intake vacuum has no other avenue but to pull fuel out of the bowl.

So with this in mind -- assuming the float level/fuel height are okay -- and I'd wager 99 to 1 that they are -- is there some condition in the carb, like something else clogged up, that would stop the fuel being sucked out by engine vacuum, while the choke is on cutting off airflow from the airbox?

It just doesn't make sense to me how, with the choke on thus shutting off airflow from the air filter that the engine vacuum wouldn't suck the gas right out of the bowl.

Thus my weakness here is this: on this particular carb type, a CV type of carb that may have some peculiarity I'm unaware of on this model -- I guess I don't get how this model of carb flows gas into the cylinder when the choke is on.

Because it's my belief that it *should* and it clearly is not.

It's not really a choke, it's an enricher. It adds fuel.

CV carb's? Not reading the whole thread but are you sure the diaphragms are fullly intact!?

With a fixed amount of vacuum created by the engine, a 'choke' normally reduces the amount of air allowed to enter so that the *ratio* of fuel rises in the fuel/air mixture. I don't think you meant "it adds fuel", I think you meant "it enrichens the fuel/air mixture, achieving this by reducing the amount of air in that mixture, by reducing the amount of air allowed in from the airbox, thus increasing the percentage of fuel in the fuel/air mixture."

So I'm back to "why is there no enrichment happening when I reduce air from the airbox, why doesn't the percentage of gas in the fuel/air mixture rise."

Then again, I'm missing something about this carb model. I don't have a shop manual for the bike, and the parts list I have doesn't give a model identifier.

missionkz wrote: CV carb's? Not reading the whole thread but are you sure the diaphragms are fullly intact!?

I've had the carbs apart, yes the diaphragms are fine. When reassembling the diaphragm there is a small 'bump' on the outer topmost perimeter rubber rim of the diaphragm that must be aligned to fit into an identically-shaped groove in the top metal body of the carb top -- where the top of the diaphragm sits just under the carb cap. You know if you get that wrong because the metal slide attached to and beneath the rubber diaphragm will not have its arc facing the engine intake side and the airbox side of the carb body.