Kz400 gets hot after 1 min of idle,white smoke

Good evening gentleman,
I have some issues and I dont lnow where to start looking.

Took apart cilinder head to fix low compression. Changed:
1.first two piston rings-the second,scraper ring,was different from the original,it did not had that "lip",it was not tapered,it was a normal straight one.
2.changed valve stem gaskets
3.cleaned valves
4.changed head gasket
5.cleaned the carb

Now,when I started the engine a lot of white smoke came out,it setteled,but now it appears only when I rev the engine.
Also after 1 minute of idle,the engine gets so hot that i cannot toutch it( dunno if its normal)

I am a bit affraid to ride it as I dont want to cause any damage if it gets hot.
Any ideeas where to look?

Spark plugs are looking wet and a bit black.
I can see traces of oil in the cylinder as well.When I remove the spark plugs there is white smoke coming out of the cylinder.
Although top part of the engine gets hot,oil pipe that provides oil to the top part is cold-ish.

Sorry for posting several thing in one topic but they seem linked.
Any advice?
Thanks

Your withe smoke can be unburned fuel or oil.
You changed valve stem gaskets,are you sure you do it right??
You can easily damage the sealing lip #4 if you not use a special tube to prevent the sealing lip
scratched by the valve stem grove for the valve keepers.





The tubes were put on the valve stem to prevent any damage of the sealing lip of the valve stem gasket (little o-rings)
The valve stem seals are sensitive by sharp edges and can destroy easily.
This then cause the with smoke by unburned oil that is leaking through the valve stem guide into the combustion chamber.
These tubes are normally in every set of valve stem seals.

Michael

Is your cam timing right? Being off a tooth could cause the heating symptoms.

Sharky wrote: Now,when I started the engine a lot of white smoke came out,it setteled,but now it appears only when I rev the engine.
Also after 1 minute of idle,the engine gets so hot that i cannot toutch it( dunno if its normal)

A hot engine will be too hot to touch with bare skin, especially if it's stationary (air cooled engines require air movement - conveniently they tend to have more air movement when they're being worked). A water cooled engine will typically sit around the 90 degree mark, depending on what thermostat is used. Air cooled can get a bit hotter. And near the exhaust outlet of the head it can get very, very hot, several hundred degrees C.

White smoke is usually water, but if you've just dismantled everything it's probably everything else. Any degreaser, lubricant or even the oil in your hands can smoke off, and it can take a while for that to burn off.

It could be oil, but that tends to burn more of a blue colour.

Agree with Irish. thinking on it a air cooled motor would be hot to the touch after a minute of run time.

Update. Found out what was the problem after taking the engine apart.
Both of the oil piston rings were broken in 2... The problem now is that i have 2 small scrapes on the wall of the cylinder...any thoughts?!

Sharky wrote: When I remove the spark plugs there is white smoke coming out of the cylinder.

Are you sure it's smoke? It sounds like it may be fuel vapor. If you shut the engine down and remove a plug, there may be unburned fuel evaporating inside the cylinder or off of the spark plug. You did say the plugs look kind of wet, so it may be running too rich.

If you perform that test again, see if you can (carefully!) determine the smell of the vapor. If it is fuel, you will know. Oil smoke has a distinctive smell, too.

Although top part of the engine gets hot,oil pipe that provides oil to the top part is cold-ish.

That pipe is unlikely to get very warm until all of the oil in the engine is warm; this will not happen with only a minute of running, so it does not sound like a problem right now.

If you have the engine fully up to temperature - say, after ten minutes of running - and that pipe is still cool to the touch you may want to investigate.

Good luck!

Funny... I was going to say you have a broken oil ring... LOL...

Anyhow... if the scratch is not absurd, gently smooth the burs off the scratch(s), vertically, with 360 wet-dry paper.
Get a cylinder hone, slip it in and out, just a few times with light pressure. You are only trying to reestablish something for the new rings to wear into.
Clean the bores with cheap automatic transmission fluid and clean cloth rag.
CHECK ALL your new piston ring's end gaps now.
Of course, use all new rings and do not over lubricate the cylinders, rings, pistons and lands when assembling!
A very thin light coat of oil is right.
You want the rings to "break into" the honing easily....

Catches finger nail.

Sharky wrote: Catches finger nail.

That's a general indication that the damage is too much for a hone and more machine work will be required. D'oh.