KZ400 project - baby steps (what's next)

Hi all,

I've tinkered around a little with that 1978 KZ400 i picked up from a friend.

Let me update you on what i have done thus far and then ask a couple questions.


- replaced plugs (gapped as per old ones as i do not yet have my hands on an owners manual - one is coming in the mail)

- replaced oil

- drained gas tank (and one carb bowl - could not unscrew drain screw for second); also took of petcock and cleaned it up with 10W40)

- bought/installed new battery (and tested electrical items: starter*, horn, right blinkers = OK; rest are questionable); *has a kick started too

- I also tested the plugs against the engine block (right one gave good blue spark and left one gave a "whitish" spark)


Today i attempted to start the bike...

- the engine DOES start, but does NOT idle (no matter what I do - played with the idle screw a little)

- I can get the bike to keep running* (for a couple mins) if I HOLD the start button down and work the throlttle, but the moment I release either (starter button or throttle), it stalls (*as if that is "running"!)

- while the engine is on, I hear a slight "screeching" sound (but I'm 99% sure that the noise is associated with continuously holding the start button - yes, of course that is not GOOD to do)

- the engine does rev a little higher/stronger (without holding down start button) if I spray some carb cleaner in.... (note: the tech does not work)

- I did mistakenly (but good in the end) start the bike in gear (it was on center stand!) and the back wheel started spinning! so, at least power is transferred to the chain/wheel...

- the most disturbing thing was that when the engine was running GAS was dripping out of some of the overflow tubes (not sure which one/ones or WHY the HECK that was happening - had a fire extinguisher in hand!)


Question:

- Can anyone explain why gas would flow from an overlfow tube ONLY when the engine is ON?


My next step:

I'm planning on taking the carbs off/out and giving them a good cleaning. I'll pop them back in and see if this helps.

Is there anything else i might want to try at the same time to get the bike to idle?

Yes, this bike is in SAD shape, but it might have some potential (beyond being parted out!), so i'm willing to give it a try....

are there other parts i should try and clean up to help the bike idle better? or simply try the carb thing first?

Anyway, if i can get the bike to hold an idle, i'll "commit" to starting other tasks (master cylander/front brakes need work and the electrical system needs LOTS of care - i suspect there are many shorts as the bike sat outside for a while).

I also wonder if any shorts in the electrical system be interferring with a good idle?

anyway, below is a pic (i think) of what my son (6yrs) and i have named "Frankin-bike"!

- prime

primemover wrote:

Question:

- Can anyone explain why gas would flow from an overlfow tube ONLY when the engine is ON?


My next step:

I'm planning on taking the carbs off/out and giving them a good cleaning. I'll pop them back in and see if this helps.

You must have a vacuum-style petcock, and a poorly adjusted float. That's my guess. When the engine is running, the vacuum is pulling fuel into the carb. Because your floats are stuck or misadjusted, the fuel is overflowing.

Your "next step" is the correct one. A good carb cleaning and adjustment.

Good luck!

i had a similar problems with my 76 when i first got it.
first thing i did was new plugs. b8es ngk or w24es denso's (these are the mids. you can go a step up or down depending on weather you want top or bottom end)
plug gap is 0.7 - 0.8 try to find the shim style gap tool,should be in your trunk.
after that i used injector carb cleaner.and im not gonne lie. my bike was hittin about 45mph at half throttle and thats all i could get.
when the cleaner kicked in i was about half throttle and i bout fell off the back when it "cleaned out"in
3rd gear.(my closest call yet)
now my bike does 98mph with no other engine mods.

to me it sounds like your firing one plug and one partially
sounds like you need a new coil. but others would know more about this than i.

wired george seems to be the resident go to guy about carbs.
and from what ive read he's legit.

i can only offer my advice on the subject because there is 2 years difference between our bikes and i do not know enough about the differances between years and models yet.

Post edited by: mykznme, at: 2006/01/10 00:19

All sounds great!

i'll work on carbs and see where that gets me....

if i can get the bike to idle, i'll prop it up on a jack stand i've got and start to work on brakes/lights...

thanks...

- prime

Your weak spark can be due to corrosion on the electrical connections in that circuit. Check to see how much voltage you have at the coil. Should be 12v but probably is not.

Buy some Electric Contact cleaner, sandpaper, steel wool or whatever it takes to clean those connections. Pull them apart one at a time, after they are clean apply Di-Electric grease (tune up grease)on all of them, put them back together.

On that weak cylinder, pull the spark plug cap from the wire and check for corrosion there. Snip off the corroded part, about a 1/4" will do it. Replace the cap and check the spark again.

Check and adjust your valves.

Go here and rejoice. www.kz400.com

Kent

will do...

thanks...

wow, sounds like you stole my bike lol. Mine was exactly like that when I got it. Every conection corroded, and had it held wide open just to keep it idling. Turned out that from sitting for so long the sliders in the carb were slightly seized and the vacuum couldn't pull them open. Tapped on the sides of both carbs and they broke loose, it reved up no problem.

hey there....

would love to hear more of your "troubles" as i move forward with this one....

i was able to get the carbs apart (piston too), but letting rubber parts sit in carb clean is, i guess, not a GOOD IDEA!

the o-rings and even one of teh diaphrams are in pretty bad shape! (good thing i have an extra carb for my KZ305 sitting around - some of the parts are the same)...

- prime