smokey on start up but not when running

[kevin nx650]

Hi All
Any suggestions,
I have a 1991 Dominator which does not smoke whilst running or seem to be burning a lot of oil but once it has been left over night it smokes for under a minute after start up, no odd noises or anything changed.

[Simon WS]

Is you crankcase ventilation system standard Kevin? If it is partially blocked on start up things will get rather smokey. I'm not too sure why a partial blockage would clear after running, but it's the first thing that came into my head (and therefore probably not the answer!)

Simon

[steved1969]

By 'On Startup' do you mean with the choke one ?

Assuming it's dark smoke (and we aren't talking plumes of the stuff) that clears up after about 30 secs then it's probably just the engine running rich when you start it. Could be worth changing the plugs as a weak spark could be the cause if it isn't limited to when the choke is on.

[sbikerbud]

if the smoke is light grey/white then its oil smoke.

Black would indicate over fueling

sure its not just steam from the zorst?

If it is just whilst starting i always thought that meant valve stem oil seals.
Oil seeps past over night, smokey when started (oil sitting on top of valves), gradually clears up (washed clean by incoming fuel/air mix), not noticable when running (due to the small amounts involved).

[kevin nx650]

Hi Guys

Thanks for the replys, the smoke is light grey and I had wondered about the valve stem seals but thought others may know more, I will check the breather system and plug this weekend as it is an easier job first, if anyone has more info please offer it, thanks again all.

Regards Kevin

[joch]

a good way to tell if the valve stem seals are faulty is if it smokes when engine braking. it might take a few seconds for the smoke to show.

[steved1969]

Sorry officer, I'm just trying to see if the engine smokes under engine braking

[BIGROG]

Stick a tractor zorst on the bike... you can monitor it as you drive, might sound good too

[joch]

or adjust your mirror...