white smoke when cold

when cold starting my 77 kz650b i have recently been seeing white smoke from the exhaust. after the engine is warm the exhaust clears and the smoke is gone. this has only become apparent after i rode in a really hard rain. the oil doesnt seem to have gas in it, could there be water in the crank case or in the fuel? or do i have a ring/valve seal problem? the bike runs strong and the smoke is the only symptom of this problem. any ideas?

thanks,
david

Rubber valve stem seals (aka valve seals) gradually harden with age in a hot oil enviornment.

With a cold engine, particularly on older bikes, the seals are at their hardest and with less sealing ability.

When the cold engine is first started, some oil in the top end seeps past the cold hard seals, down along the valve stem into the combustion chamber, which burns and smokes out through the exhaust. It usually doesn't harm anything, nor does it consume much oil. Just looks bad, and maybe kills a few mosquitoes.

The smoking is often temporary until the engine reaches normal operating temperature, where the heat softens the seals, which then resume better sealing, and eliminates the smoking exhaust.

Whenever the head is removed for some other reason, imo then is usually a good time to also consider renewing the valve stem seals.

Good Luck!

If unsure, next time it's off consider both valve guides and seals. I have made that mistake once before.

Well I had the same occurance only 1 time.

It was after I started the bike after I got caught in a downpour.

No worries. I keep the bike indoors and out of the rain.

I do not know if it was residual water that turned to steam and pulled some disolved crud out the exhaust.

Small potatoes.

KR

I realize this may be a different situation then yours but here goes anyways....

My KZ is doing the same and this is after a complete head valve, seal, guide, springs and P&P job....

I thought WTF, check my valve clearances, timing components, ignition, carbs you name it.... Then I came across this....

If replacing valve seals, stick with Kawi OEM Seals for after market seals have a tendency to do this...

Just a thought in case you just had work done in your head....

OMR

Old Man Rock wrote:

If replacing valve seals, stick with Kawi OEM Seals for after market seals have a tendency to do this...

If they are available, Kawi hasn't sold the seals for the twins in a long time.

FYI: get Viton seals if you can, they last a lot longer than butyl rubber seals and seal a lot better.

Patton wrote:

...enviornment....

Edit Once upon a time knew how to spell .environment :laugh: :laugh:

Patton wrote:

Patton wrote:

...enviornment....

Edit Once upon a time knew how to spell .environment :laugh: :laugh:

It's funny, I never realized I was a little dyslexic until I started posting and typing a lot. I flip letter pairs like that all the time, sometimes I flip two letter sets in one word. I usually notice when I proofread the post, not always.

Someday, they will invent something that let's us go back and change a post if it has mistakes in it..... what a day that will be.:laugh:

Is the smoke white or blue. oil tends to make it smoke blue. not sure about white smoke form a air cooled bike.

This is copied out of my KZ900 Shop Manual... Should be exact or close to your KZ650 as well....

White smoke after any rain,,,,,,,,
I would think condensation,
If it happens more then twice after the bike has been warmed up.
Check your air filter/filters to make sure there is no water sucked into it/them.

White smoke is actually steam, You'll see it on cooler days especially if the humidity is high.

Oil, as was previously stated, tends to have a bluish tint to it, and will have a distinctive odor. Burn some motor oil if you want to know what it smells like, or ride behind a two-stroke.