Oil

[Sev]

Idling around all the time will promote carbon build up. But so long as you rev it out afterwards you should burn off the carbon. Which isn't to say "test the rev limiter." It is to say take it up to highway speeds.

Besides, why on earth would you want to sit there and "wait for it to warm up?" Get it choked, once you can run without the choke on and not have it bog down as you apply throttle then go. That's pretty much warm enough to ride at that point anyways.

Don't choke overlong, and don't idle overlong if you can avoid it.

[ofblong]

Actually, you get condensation in the cylinder... not on the crankshaft.

What happens is the engine warms up a little, but there's still moist humid air inside if you only allow it to idle for a short time. So as the engine cools down, condensation forms on the cylinder walls. This condensation can cause rust, as there is usually little oil in this area (the second oil control ring having scraped it off the side of the wall).

Rust is obviously very bad for the engine.

The best thing you can do to prevent this is get the engine up to operating temperature every time you run it. And running it longer is better then running it for a short time.

If you're getting condensation on the crankshaft there is no oil in the engine.

well I was told this by many auto mechanics who had been doing auto work for YEARS and most of them are either friends of my fathers or ones I have talked to while they work on my vehicles.

[Sev]

You could be right... but I fail to see how condensation can form on something that is submerged/coated in oil. And if it were to do so... like if it were to form around the crankshaft, wouldn't gravity and the relative density of oil vs water cause the water to settle to the bottom of the sump?

And come to think of it, where is the water coming from that condenses on the crankshaft? The bottom end of the engine is basically sealed (you get a TINY amount of combustion product that blows past the rings), how could you get enough air in there to have water condense? Actually, in a rollerbearing engine that's vented to atmosphere you could get the air in there, but not a plain bearing (more and more bikes are becoming plain bearing).

Also, wouldn't it make more sense that it would condense on the sides of the aluminum engine case that cools off much faster then the steel crankshaft? It's cool objects that cause condensation, not warm ones.

Finally, why is it freezing? Or, are we talking about over-winter storage?

I know that rust rings where pistons have sat for a substantial (off season) amount of time is a big problem because the condensation pools around the rings and rusts the iron cylinders.

*edit* or are we talking about 2 strokes where there is no oil in the bottom end? Then I could see something like that happening... but even then, there should be an oil film coating the crankshaft from the oil injection through the carb.

[niterider]

The man said that the moisture is condensing in the cylinder not the cranshaft. He corrected himself. Also the crankshaft does not run submerged in the oil. It is lubricated by the oil pump pumping oil through oil galleries drilled through out the engine. The oil pan is there to hold the oil. The inside of the engine is not like a washing machine. the oil just sits at the bottom and is pumped not splashed. I hope this makes sense.

[Sev]

Check again, he said crankshaft. I said cylinder. and a fair bit of the crankshaft rotates through the oil in the sump. The bearing surfaces have oil pumped into them to prevent contact between the crank and the case.

[niterider]

Sev are you motorcycle mechanic? I deal in automobile engines and I know that the crank does not run in the oil in them. And if the PCV valve is bad it will form water in the engine.
I can understand how moisture can form on the cylinder wall, because on the big trucks, in winter time the brakes will sweat after use, and if set they will freeze to the brake drum over night.

[scan]

Greater point to be made here.... Condesation will not occur if you follow the rule of getting the engine to operating temp, which means don't just idle the engine and then shut it down. It needs to be operated for a 15 or 20 minutes beyond idle to avoid this problem. Letting your bike idle before you ride is not required on some bikes, but I know mine doesn't like to go smooth unless I let it runs for a minute or two before I ride.

Now where the condestaion occurs, the crankshaft seems unlikely. It does not heat up to a great extent, compared to the piston or cylinder walls, and even with water on it, it seems unlikely in the crank journals, where the connecting rod contacts the crank, that any water could work its way in. The tolerance is very tight in the rod bearing. So I say condensation on a crank would mean nothing. On the cylinder walls, that could be a problem - regarding rust as Sev mentioned.

There are my 2 cents.

[SilentComposer]

Well now I have a different problem. It seems even when I do get the engine warmed up and all. When I go to stop and am in first gear if I let it idle it usually stalls... Any reason why this could be happening? And yes I do have the clutch pulled in

Also could anyone recommend what the tire pressure should be at for a 2000 EXNinja 250? I still don't have the service manual yet.

Thanks in advance.

[ANDS!]

Get a fuel inject bike. Idle wackiness solved.

[ofblong]

Well now I have a different problem. It seems even when I do get the engine warmed up and all. When I go to stop and am in first gear if I let it idle it usually stalls... Any reason why this could be happening? And yes I do have the clutch pulled in

Also could anyone recommend what the tire pressure should be at for a 2000 EXNinja 250? I still don't have the service manual yet.

Thanks in advance.

I could be wrong but I thought all bikes had the recommended tire pressure on the swing arm???