KZ400 idle issues, running rich.

[doc_rot]

I have a 1978 KZ400 deluxe. It has an erratic idle once it gets hot and wont come down below 2000. It rides pretty good, but a bit of hesitation in the midrange. #2 cylinder is slightly rich, #1 looks perfect. There is some weirdness going on with the timing, I dont think its part of the problem, i only mention it to cover all bases. I set the timing per the FSM using a ohm meter to determine when the points are opening. However when i check it with a timing light it is advanced. I set it by idling the bike and turning the points plate until the marks line up. not sure why it does this.

Here is a list of the things i have done;

adjusted valves,
cleaned and lubed advancer.
set point gap
set timing
cleaned carbs THROUGHLY
carbs completely rebuilt, with OEM pilot jets
new diapraghms in carbs
replaced jet needle holders with used good condition ones off ebay
carb floats set with tube
carbs synced
new carb holders
Air box boots are hard but appear to be in OK condition, doesn't seem to be any leaks.
New OEM air filter
compression is good 150PSI on both
tested spark plug wires - good
new spark plug caps
new spark plugs
stock exhaust with new gaskets, no leaks.

I am at my wits end here, i don't know how to proceed.. heeellllppppp!

 

[2_DONE_THE_TON]

Did you try to spray some brake cleaner beside the hard carb boots to see if its really now leaking?you should see it in the rpm when its running when it sucks air.
had this issue with my kz with the boots touch connect the motor with the carbs.

 

[Armaundk]

You'd be surprised how difficult points are to set just right, so try turning the timing plate while the bike is running and with a timing light so you can see the effect in real time.

Also, try using an unlit propane torch around your airbox and intake manifolds to check for air leaks. I think that's probably safer than using brake cleaner around rubber parts (no disrespect to Mr. Stecken.)

 

[2_DONE_THE_TON]

You'd be surprised how difficult points are to set just right, so try turning the timing plate while the bike is running and with a timing light so you can see the effect in real time.

Also, try using an unlit propane torch around your airbox and intake manifolds to check for air leaks. I think that's probably safer than using brake cleaner around rubber parts (no disrespect to Mr. Stecken.)

You can also use WD40 doesnt really matter.brake cleaner is bad for your paint

 

[doc_rot]

You'd be surprised how difficult points are to set just right, so try turning the timing plate while the bike is running and with a timing light so you can see the effect in real time.

Also, try using an unlit propane torch around your airbox and intake manifolds to check for air leaks. I think that's probably safer than using brake cleaner around rubber parts (no disrespect to Mr. Stecken.)

This is how i set the timing because the ohm meter method wasn't working. timing appears to be set OK. Also i tried the WD40 method, no change in idle.

 

[barnett468]

.
1. use FLAMMABLE brake cleaner with the long nozzle . . do NOT use wd40 or non flammable brake cleaner.

2. the timing lit does not lie . . your advance springs may be weak . . your timing MUST be correct to proceed PROPERLY.

3. try adjusting the fuel mix screw.

4. back the idle speed screws out all the way . . if it still idles, you have an air leak, its that simple.

 

[doc_rot]

triple checked for air leaks with carb cleaner, none apparent. This bike has a pilot circuit and no mixture screw. Timing is spot on, checked again.

the throttle butterflys seemed to not quite be closing all the way, leaving the pilot circuit bypass slightly open so i readjusted and reinstalled. IDLE ISSUE GONE!!! however it still was hesitating at the middle of the power-band, and rich in #2.

I then switched the slides and needles in the carbs and it drastically reduced the hesitation. It will rev all the way to redline now under load. A very slight hesitation remains, and it still was a bit rich in #2 though. I have bought some OEM needles off ebay (dont trust K&L). The spark plug wire for #2 seems a bit fiddly at the coil connection so Im going to order a new coil and wires just for peace of mind.

suggestions?

 

[barnett468]

.
post photos of the plugs.

if one plug is moist, it is burning oil.