Burning Oil?

[Kat-A-Tonic]

Hi All,

I was looking at my oil level on the Kat this morning and I've noticed that the oil level is slightly down from the previous oil change. We're talking about 4 ounces of oil. Currently, I've clocked over 4000km since the last oil change.

I haven't seen any blue smoke from the exhaust. My personal take is that a small amount of oil will be consumed naturally over the course of it's life within a motorcycle engine. Is this, however, something I should be concerned about?

Any input would be appreciated.

[DreKat]

Have you noticed an oil on the ground, I noticed that I had oil leaking from the oil cooling lines that run from the engine to the rad. so I replaced the copper washers and it fixed the problem. You are right that the engine will eat up some oil.

[The CyberPoet]

Re: Burning Oil?

I tried to reply to this last night right after you posted, but KR started acting up again.

1 ounce per 1000km is well within the reasonable limit of oil consumption, especially if the engine has been run particularly hot (such as while syncing carbs or otherwise not moving).

If I recall, Suzuki's guidelines are a half liter per 1000 miles (1500 km) to be classified as defective.

I suggest you open your air box drain tube cap (engine off) and let it drain for several minutes... If you find more than an ounce in there, then it may be reasonable to go looking for reasons IMHO.

Finally, a lot of it also depends on what oil you are running. JASO-MA oils have very tight tolerances on evaporative loss, but just plain API SF/SG oils don't.

Cheers
=-= The CyberPoet

[Kat-A-Tonic]

Re: Burning Oil?

Finally, a lot of it also depends on what oil you are running. JASO-MA oils have very tight tolerances on evaporative loss, but just plain API SF/SG oils don't.

Cheers
=-= The CyberPoet

I'm using Castrol's Grand Prix motorcycle oil, which appears to be JASO-MA certified (they're on the list provided by JASO). However, there doesn't seem there is a lot of oil loss. We're talking a quarter of a quart so it tells me the problem isn't out of line with significant use.

Thanks again CP.

[Kat-A-Tonic]

Have you noticed an oil on the ground, I noticed that I had oil leaking from the oil cooling lines that run from the engine to the rad. so I replaced the copper washers and it fixed the problem. You are right that the engine will eat up some oil.

There's no oil on the ground or anywhere that I can see. I took a good look around to be sure. I just want to make sure I'm not seeing an engine problem starting to evolve.

Thanks for the suggestion.

[The CyberPoet]

Let's see if I can clarify this a tad bit more:

There are two times that your oil burns off normally (i.e. - without specific mechanical failure):

(1) When your piston comes up to compress the fuel-air mix, oil is being sprayed up against the underside of the piston and coating the cylinder walls. When the piston gets forced back down by the detonation, the oil wiper ring gets most of the excess oil off, but some of it stays (to lube the rings) and some oil will be stuck on the walls of the cylinder. The stuff on the wall gets a double-whammy: first it gets hit by a fuel mixture (which immediately begins ripping the exposed oil apart chemically), then it gets hit by the detonation temp/pressure/flame. When the detonation flame hits this exposed oil (at temps of 1200 - 1500 C), the oil on the exposed part of the walls immediately flashes and goes out the exhaust pipe as a vapor/smoke mix.

(2) When the upper engine gets particularly hot (such as highway driving followed by a traffic jam), oil running over the exhaust valves and the area directly above the cylinder may reach the flash temp of the oil as well, in which case, the vapors are drawn through the top of the valve covers out through the tube to the airbox (by vacuum) to be recirculated with the next inbound fuel-air charge going into a cylinder. The same thing happens with any fuel that gets past the rings (it vaporizes and gets drawn back to the airbox as well). As long as the oil vaporization level is within reason, the stuff won't condense out of the air before getting sucked back in to the carbs to be reburned normally (perhaps a few drops per thousand km will condense out).

When you run into serious problems (bent or burnt valve, excessively worn rings), the volume of vaporized stuff being sucked back into the airbox is sufficient that you get a lot of condensation of those vapors going on and the airbox fills up with fluids (which run down the drain tube until it fills up all the way, then starts filling the airbox itself).

Draining the airbox drain tube will normally tell you if there is something going on that you need to be concerned about -- based solely on how much fluid is recovered from the drain (standard procedure is to drain it at each oil-change interval).

Cheers,
=-= The CyberPoet

[Kat-A-Tonic]

Draining the airbox drain tube will normally tell you if there is something going on that you need to be concerned about -- based solely on how much fluid is recovered from the drain (standard procedure is to drain it at each oil-change interval).

Cheers,
=-= The CyberPoet

Ah...OK then. I'll take a look at the airbox drain tube and see what's going on. Thanks again!