Will not restart when hot

Ok I have a 83 KZ550M1 with 24xxx miles on it. When it is cold it starts right up and idles fine. I take it for a 10 min ride turn it off and try to restart it and nothing. The motor spins fine but will not kick over. If I let it sit for 10 mins it will start right up. Any help would be great.


Matt
Mantua, New Jersey

Before getting into possible theories of what may be the cause....

Once started and during a ride, are you noticing any difference in performance such as acceleration, back fire or exhaust popping during deceleration, lack of power, flat spot/lining on power, running sluggish etc....

Or coming to an intersection, pinging noises, have to keep on the throttle to keep it running, slow take off's from dead start or does it sluggish then all of a sudden run like a raped ape etc....

When you say hot, normal temps or are you noticing more than normal heat build ups?

On cold or hot start up, smoke out the exhaust?

Ignition timing good?

Valve clearances good?

Spark Plugs look good?

Battery voltage good?

Proper voltage @ coils?

etc....

OMR

Several places to check:

1. Valve clearances,metal expands when hot,possibly a valve or two partially open letting compression out.

2. Sparkplug wires and caps age and loose conductivity.Replace and try again.

3. Ignition coil(s) fail when hot. Where the coils are mounted can heat stress them causing failures.

4. Check all heavy duty battery connections for tightness and traces of corrosion. All must be clean and tight.

There is no difference in performance. The bike does back fire realy bad during deceleration. It is a little sluggish on take offs then it will just pull the wheel off the ground. It does it at norm temps of riding. I do not know how to ckeck the timing plus I need to get the specs on the valve clearances, and the plus are new and gapped right.

MFolks wrote:

Several places to check:

1. Valve clearances,metal expands when hot,possibly a valve or two partially open letting compression out.

2. Sparkplug wires and caps age and loose conductivity.Replace and try again.

3. Ignition coil(s) fail when hot. Where the coils are mounted can heat stress them causing failures.

4. Check all heavy duty battery connections for tightness and traces of corrosion. All must be clean and tight.

All wire and plugs checked and ground wire replaced.

"The bike does back fire really bad during deceleration. It is a little sluggish on take offs then it will just pull the wheel off the ground."...


Assuming all other mentioned items are within specification (please insure you measure/adjust to specifications) before going after your carbs... Best guess at this time is carburetor issues...

Most likely running lean thus over heating engine...
Either main/needle jets not the right size or gunked up etc...

I don't know your carbs (someone here should) so if the needle jets are the clip version, you need to richen it up by changing the clip position. If all is working, you should hear a difference in the exhaust popping...

Again, assuming they're the correct jet but just wrong clip position...

What do the insulators and end of thread base look like on your spark plugs?

OMR

EgoCrusher wrote:

There is no difference in performance. The bike does back fire realy bad during deceleration. It is a little sluggish on take offs then it will just pull the wheel off the ground. It does it at norm temps of riding.

That sounds like a very lean pilot jet, needle set too lean, or a vacuum leak. Either will make it hard starting. The easy start cold is probably because you can use the choke which riches it up.

Does the bike have aftermarket pipes and/or pod air filters?

bountyhunter wrote:

EgoCrusher wrote:

There is no difference in performance. The bike does back fire realy bad during deceleration. It is a little sluggish on take offs then it will just pull the wheel off the ground. It does it at norm temps of riding.

That sounds like a very lean pilot jet, needle set too lean, or a vacuum leak. Either will make it hard starting. The easy start cold is probably because you can use the choke which riches it up.

Does the bike have aftermarket pipes and/or pod air filters?

is the pilot jet the one that is on the top of the carb motor side? The pipe have been gutted by the last owner and it has the stock air box.

Old Man Rock wrote:

"The bike does back fire really bad during deceleration. It is a little sluggish on take offs then it will just pull the wheel off the ground."...


Assuming all other mentioned items are within specification (please insure you measure/adjust to specifications) before going after your carbs... Best guess at this time is carburetor issues...

Most likely running lean thus over heating engine...
Either main/needle jets not the right size or gunked up etc...

I don't know your carbs (someone here should) so if the needle jets are the clip version, you need to richen it up by changing the clip position. If all is working, you should hear a difference in the exhaust popping...

Again, assuming they're the correct jet but just wrong clip position...

What do the insulators and end of thread base look like on your spark plugs?

OMR

the jets are120. And I need to buy a book for the bike unless someone has a PDF file they would like to share.

EgoCrusher wrote:

bountyhunter wrote:

EgoCrusher wrote:

There is no difference in performance. The bike does back fire realy bad during deceleration. It is a little sluggish on take offs then it will just pull the wheel off the ground. It does it at norm temps of riding.

That sounds like a very lean pilot jet, needle set too lean, or a vacuum leak. Either will make it hard starting. The easy start cold is probably because you can use the choke which riches it up.

Does the bike have aftermarket pipes and/or pod air filters?

is the pilot jet the one that is on the top of the carb motor side? The pipe have been gutted by the last owner and it has the stock air box.

Not sure where they are on yours. You can look up the carb diagram on babbittsonline.com and it lists all the parts.

If the baffle is out of the pipe, it could be running very lean.

EgoCrusher wrote:
And I need to buy a book for the bike unless someone has a PDF file they would like to share.

Here is a manual link courtesy of loudhvx.
home.comcast.net/~loudgpz/KZ5mnl.pdf

I'm betting you have one or both coils going bad. I had problems with a bike years ago that would run like a scalded dog from one place to the next but when you shut her down and it cooled off it would not start. A mechanic told me the coils were "breaking down" and needed to be replaced. After replacing the coils it ran great after that. Check your coils and see if thats the problem. Good luck. Tom