Oil smoke at cold startup

[relic-rider]

Well, since I got my carbs fixed from leaking down into my crankcase, now I get a fair amount of oil smoke at cold startup. The smoke comes out of both pipes equally. This only happens after the bike sits overnight. When it sits for 4hrs it doesn't do it. It goes away right after it warms up. Could this be valve stem seal leakage? Did running it a short while with some gas in the oil cause them to start leaking? Or did my changing oil to Castrol Syntec have something to do with it? It starts great, even when cold. Usually only one short tap on the starter and shes going. Or could it be excess oil getting into the carbs through the vent tube from the cam cover to the airbox. Seems to me that the carb slides seemed to have a little oil residue on them when I took them off. Whats up here?

[kalessin]

Is the smoke plain white, as in water-vapor white (condensation collecting in your exhaust)? Or is it a bit bluish in strong light, as oil would be? Is there a huge lot of it when you do a cold startup?

[relic-rider]

It is oil smoke and it has a slight blue tinge to it. It kind of hangs around in the garage a while. And it smells of oil. I'm a vintage snowmobile freak(10 of em), so I know oil smoke! Did it again this morning, left a big old fog cloud floating over to the neighbors. This is kind of embarrassing, dontcha think.

[tfb]

Yep it does get a bit embarrassing. Like the time I filled an entire huge car park with smoke from my old z400...

Sounds like it is indeed leaking down the valve stems. If it doesn't smoke on a warmed-up engine under load (eg. when accelerating), then I'd assume the oil is indeed getting down the valves stems and into the combustion chambers while it's parked up.

Might as well do the lot while you have it apart: valve stem seals, perhaps replace the valve guides if they are really worn, and pop a fresh set of piston rings in with a light hone (assuming pistons & bores are within tolerance). Then it'll all be right for another 20 years!

Mike.

[JHawkins]

It is oil smoke and it has a slight blue tinge to it. It kind of hangs around in the garage a while. And it smells of oil. I'm a vintage snowmobile freak(10 of em), so I know oil smoke! Did it again this morning, left a big old fog cloud floating over to the neighbors. This is kind of embarrassing, dontcha think.

It sure sounds like valve seals since it goes away when warm.

I had an old Nissan Sentra with bad valve seals. I used to go start it then walk away until it warmed up so nobody would see me with the huge cloud of smoke! Hehehe.

[carlosjc401]

yes I agree with the others it's seals

[Road_Clam]

Well, since I got my carbs fixed from leaking down into my crankcase, now I get a fair amount of oil smoke at cold startup. The smoke comes out of both pipes equally. This only happens after the bike sits overnight. When it sits for 4hrs it doesn't do it. It goes away right after it warms up. Could this be valve stem seal leakage? Did running it a short while with some gas in the oil cause them to start leaking? Or did my changing oil to Castrol Syntec have something to do with it? It starts great, even when cold. Usually only one short tap on the starter and shes going. Or could it be excess oil getting into the carbs through the vent tube from the cam cover to the airbox. Seems to me that the carb slides seemed to have a little oil residue on them when I took them off. Whats up here?

My bike behaved in the exact same manner (see my post about tearing down a GS top end). In hindsight, I had a weeping h/g, and all four intake valves seals were junk. My bike sat dormant for 4 years, and after re-awakeining, I trashed all the 24 year old gaskets and seals. Its very common knowledge that the demise of most older bikes, is not high milage, but extended periods of NO milage.

[scotty]

yes I agree with the others it's seals

yep seals :-D

[relic-rider]

Ok, thanks all. I'll plan on taking it down this fall. I can live with it now and will wait to give the top end a rebuild. A couple of exhaust bolts were broke off by the previous owner and the holes were cobbled up with a drill, so I can fix those then. The guy I got it from did let it sit for about 5 years before I got it. I put on 125 miles this past weekend up in Northern Wi. I'm going to take the motorcycle BRC later this spring, so I need to get a little practice in.

[rckrzy1]

I hope none of the mains or cam bearing got wore out with gas oil mixture, I think they would be damaged as well. If you have roller's on the mains then you might be ok.