KZ550 no start *Updated*

Well I have more trouble with my bike, KZ550C3.

Just like last fall, it is very hard to start. When it does start, it revs to 5000 rpm, then
dies. I can keep it running with the throttle.

This spring I have replaced many parts, related to the engine.

Valve lash checked and adjusted.

Cam timing checked.

Carbs torn down and rebuilt with K&L kits. Carb passages blown out with carb cleaner
and compressed air. Float levels checked and adjusted. Choke flaps glued in place.
Carbs bench synced, and fast idle set according to FSM.

New carb holders and airbox holders.

Clean air system removed.

Vacuum caps on carb holders. New carb vent hoses. New vacuum line to petcock.

New fuel line with in line fuse.

New NGK spark plugs. New copper core ignition wires.


I have no idea what else to do. This feels like a vacuum leak but I done see how
that is possible with all the new rubber.

If you have the flaps glued shut, you have to make sure the choke is closed all the way before starting, but then open it as you hit the starter. Eventually you will find the right combination.

Also, the relationship between the high-speed idle setting and the choke becomes more important when the flaps are glued. The high-speed adjustment screw can only be reached with the tank off, so it's inconvenient.

Here's a way to make it much easier to get to:
home.comcast.net/~loudgpz/GPZweb/TK22mai...astIdleScrewMod.html

With the carbs on and airbox installed, you can't see the choke plate position, but you need to set them carefully when the choke flaps are glued. You can set them equally without removing the carbs: Take the tank off, remove all four carb tops, loosen the screws for the choke plate arms, then close the choke most of the way and make sure all four choke plates are seted all the way down. Then tighten the screws. This is essentially "synchronizing" the choke plates, since they will effectively act like throttle plates while the choke is on.

Now, all of this assumes there is no other big problems like a vacuum leak, as you said you suspected. Apbling ran his bike with flaps glued shut and had success, but said it takes a lot longer before you can ride the bike.

I'm trying to get some flaps made to sell, but it's probably going to be awhile.

Just curious, why did you replace the vent hoses? They usually never go bad.

Did you do a compression test? What were the numbers (hot)?

I haven't done a compression test. I can't keep this thing running long enough to warm it up.

The carb vent lines were replaced because they were hard.

And the carb slides are set with the choke lever up at the detent the slides are all the way down.

Do all four plugs look the same?

The old plugs, Champion resistor plugs, all looked the same, and looked pretty good.

I didn't pull the new NGKs. Had to quit for the night. Wife and a job limits my time.

Do the choke plates need to be set differently?

I have also been thinking the ignition advancer is stuck. The screws holding it in are stripped out thought.

4-3-2-1 left to right in picture.

These are brand new NGK plugs, after a few minutes of running at approx. 5000 rpm. Gapped at .020 in.

The_Proletariat wrote: ...KZ550C3...very hard to start. When it does start, it revs to 5000 rpm, then dies. I can keep it running with the throttle...Carb passages blown out with carb cleaner and compressed air. Float levels checked and adjusted...fast idle set according to FSM...feels like a vacuum leak but I done see how that is possible with all the new rubber.

The_Proletariat wrote: I haven't done a compression test. I can't keep this thing running long enough to warm it up....

The_Proletariat wrote: I have also been thinking the ignition advancer is stuck. The screws holding it in are stripped out thought.

Perhaps there is some mechanical issue preventing the slides from fully closing when the throttle grip is released, such as kinked or binding or frayed cable, insufficient cable slack, etc. Or the idle screw needs adjusting to further lower the slides toward reducing idle rpm.

It might be possible to lube the advancer weight arm pivots by access through the timing inspection window.

The advancer is secured by a single bolt screwed into the end of the crankshaft.
Removal of the round plate holding the pickup coils (three screws), plus removal of the single bolt, should allow the advancer to be removed for inspection cleaning, lube, and possible repair. Perhaps the springs have become stretched, being thereby unable to adequately pull the advancer closed as they are supposed to do.

Would also assure that all four clamps are tightened that hold the carbs onto the carb holders.

Good Fortune!

#2 definitely looks different,so there may be an issue there. Maybe float levels or a vacuum leak.

But, things should be checked in order.

The first step is a compression test.

Then check the ignition for reliable spark, and timing.

Then move on to the carbs.

If the chokes slides are just removed and re-installed, without checking the position, some may be more closed than others. They should all be set basically the same.

The_Proletariat wrote:

4-3-2-1 left to right in picture.

These are brand new NGK plugs, after a few minutes of running at approx. 5000 rpm. Gapped at .020 in.

Thinkin the gap should be .028 to .032 instead of .020. I shoot for .030 to .031 myself. Probaly not the problem fixer though.

Tore down the carbs again, verified a clean pilot circuit. Observed cleaner spray into throttle bore.

Removed the ignition advancer, it was not stuck in the advanced position.

Re checked float levels with a clear hose.

Re tightened all carb holder clamps.

The throttle cables are new and properly adjusted.

The throttle slide heights were set with a drill bit as a feeler gauge. The throttle slide adjustment screws are near the middle of the range to allow for a vacuum adjustment if this bike ever runs.

Picked up a multimeter and will start probing the ignition system next weekend.

This may be going to the shop soon if I cannot figure this out.

The_Proletariat wrote: I have also been thinking the ignition advancer is stuck. The screws holding it in are stripped out thought.

What screws are stripped?

Good Fortune!