Very very annoying problem with my KZ750

Just check all your clearances first. Often you can swap a large gap for a tight one, and they will fall back into spec.

You don't have to make a gasket at all. Use permatex "form a gasket #2" liquid gasket. The stuff works fantastic, and all you have to do is smear a thin film with your finger on both the surfaces. Clean the surfaces first by wiping them with some brake cleaner or similar de-greaser that leaves no residue.

This stuff is designed to be easily removed, if necessary you can just pluck it off with your fingers.

Anyways... before all that stuff... have you tried to set your mixture screws by ear yet (via the Honda method)?

With the bike idling, turn all of the mixture screws (out or in) 1/4 turn. If you hear the idle speed increase then turn them all out another 1/4.
Do this until there is no audible increase in rpm (find the high rpm spot).

This is a ballpark method for tuning the mixture screws, that doesnt require a sensitive/accurate tach or vac guage, and actually works quite well if your carbs are all clean/timing is good/engine good/nice clean spark and plugs.

Try it, might just solve your problem... especially with a K&N droppped in there.
...and yeah, there are no overflows on those carbs. if they're over flowing is goes right into the engine/air box.
Check your float levels after the bike has sat overnight (via the clear tube method). and always turn gas off.

GL!

Just a quick reply,

here's the valve clearance (double checked)



looks very good...


i will reply later today when i will have a lot more time


thanks and take a look at the picture,


regards,
laurent

Yup, they look good. Sorry to send you down that road, but at least you can eliminate that from the troubleshooting.

Anyways... before all that stuff... have you tried to set your mixture screws by ear yet (via the Honda method)?

With the bike idling, turn all of the mixture screws (out or in) 1/4 turn. If you hear the idle speed increase then turn them all out another 1/4.
Do this until there is no audible increase in rpm (find the high rpm spot).

If i understood correctly... i reset the carbs to the factory screw turns then after that i find the high rpm spot until the rpm doesn't increase anymore then i just calibrate the idle rpm adjustment.

This method look nice because i can test it live.

BTW, is the valvetrain clicking noise coming from the valve who has the most clearance ... like the one who has 0.17mm of clearance?

thank you very much!

laurent

Yup, they look good. Sorry to send you down that road, but at least you can eliminate that from the troubleshooting.

Hey no problem, now at least i know that everything is fine and i got a bonus with that...

My gasket making art skill are now improved! :silly:

Took me 2 hours to make..its the hardest gasket i had to do in my life! All those curves/holes damn it !

I have to show it

Hurray it's finished, perfect fit and no leaks.... yet !




regards,
laurent

ELCouz wrote:

Hurray it's finished, perfect fit and no leaks.... yet !

regards,
laurent

That's awesome! In my opinion, that is better than any artwork I've seen in a long time.

I have a buddy at Felpro, maybe he can get you a job there, but I don't think they cut them out by hand there.

ELCouz wrote:

If i understood correctly... i reset the carbs to the factory screw turns then after that i find the high rpm spot until the rpm doesn't increase anymore then i just calibrate the idle rpm adjustment.

This method look nice because i can test it live.

yes, thats correct. Turn them all quickly 1/4 turn and listen...

BTW, is the valvetrain clicking noise coming from the valve who has the most clearance ... like the one who has 0.17mm of clearance?

More than likely
If you ride for 30+ minutes with some good higher speeds, then that clicking will diminish considerably as the engine starts to reach full temp.
These big old air cooled beasts are very efficient at cooling, and take a LONG time to get real hot.

Check for leaks at the carb boots. Leaks will become increasingly worse as temps rise. Also did you have problem prior to carb sync? Should have air screws at factory specs prior to syncing. No expert here but have been through a few kz carb problems. hope this helps.

Hi,

After cleaning & rebuilding the whole carb rack and rejetting to the correct pilot jet (#40 instead of 37.5) everything is number one in the mixture (no flat spot during moving or bogging) except that when i wait 5-10 minutes without moving the idle gradually want to stall. I must always blip the throttle...

This maybe indicate that the mixture is still too rich but heck... each time i screw in the mixture screw half turn it's harder to start when cold !!!!

Everything is perfect when i check the engine with the colortune plug (orangist blue flame) but when i have a prolonged stop everything is different....

Do i am hitting the carburetor design limits (i'm more a fuel injection type of guy) ?
I mean it cannot adapt to condition and the mixture is always changing if engine temperature is going hotter or colder... ???!!!

thank you,
laurent

Also did you have problem prior to carb sync?

Yes the problem always there since i've purchased it.

Sync or not synched it's still there...

Check for leaks at the carb boots. Leaks will become increasingly worse as temps rise.

wouldn't that make the mixture leaner ? I guess my problem with the idle that start bogging then stall is a rich one.
Lean idle the rpm stick right ?


EDIT:

Ok i think i've found the problem but not the solution yet!

After riding in the city traffic for a while for testing... i came to a long test stop ... bang start to rattle and want to stall when the symptom occured. I've headed back to home and quickly changed the spark plug to my colortune one. The idle mixture is too lean when very hot... if i raise the rpm idle screw it will idle ok at 1100 rpm but then when it will be cold the rpm will go to 1500-1600 rpm for idle!!!

There's something wrong with the mixture that i cannot change.... !!

regards,
laurent

spray some wd40 around the intake boots while idling,and listen for a change of sound.
it is posible for a crack in a boot to increase in size and lean out the mix.