Please help - high oil consumption

[RedRupert]

Originally Posted by Orange Toaster

A hard ridden bike with 90.000 km's on the clock that still only uses 0.3 l per 1000 kms is nothing to worry about at all. Good, actually.
Especially as KTM states that it is normal.

Are you using 10W-50 oil like the manual says? If you only use 40 oil, change to 50 which is thicker and will probably reduce oil consumption.

OT

I'm using 10W60. I started using it before the engine rebuild, and continued after, in order to try to cut down on oil consumption. I like it because the motor seems quieter during high (35 - 45 C) ambient temperatures. I never ride in temps below about 10 C.

I would agree with you if it was a bike built with 1980's technology, but 90,000 km is nothing for a conservative modern motor (normal power for a 950 twin and not particularly high revs/piston speeds). The Nikasil bore showed no signs of wear - I could not feel a step between the area where the rings had made contact and where they had not. The surface colour was a little different, but the original honed surface was still very much visible. The Nikasil is very, very hard - really much better than previous common bore materials.

The piston-ring end gaps were/are well within the service limit (was 0.30. limit 0.50 mm).

The bores had the original finish, then the honed finish, but oil consumption was the same in both cases.

My leak-down test suggested a good seal, but as I have not experience re leakage tests, I'm not sure of the conclusions that can be drawn from them.

For these reasons I find it hard to believe that bore/piston/ring condition is responsible for the high oil consumption. But I don't know enough to be sure.

Thanks for your input - it helps me think it trough.

[RedRupert]

Originally Posted by azcagiva

If it were me I would try running some non syn. I have access to break in oil, you might be able to find some. The zinc and phos do help the rings seat(this is waht the guys at total seal rings have told me). It sounds like your top rings are seated maybe the dino oil will help the oil rings. Won't hurt to try.

-John

Point taken. I should have used lawn-mower oil (or similar) after the rebuilt, if only to rule out the too slippery oil theory. I'm certainly not saying that I don't agree with you. Here in the Soviet Union, I expect it'll be hard to find proper running-in oil... maybe I should drain it out of a new Yamaha!

Looking at my leak-down results, do you think that ring seating could be the problem?

Thanks.

[charlie264]

Compression is good. Did you change the oil rings. What’s the filter like?

[RedRupert]

This is my rear plug. Removed after around 5000 km, during high oil consumption:



Is it a plug from a cylinder that's burning too much oil (0.34 litres/1000 km)?

I think the dry black soot around the outside is completely normal. And the rest looks pretty good - maybe it shows the fuel/air ratio to be a bit weak?

But there's a lot of oil on the sealing ring! I've just noticed it. Is it oil? It looks like it.

Maybe the pressurised oil from the cam-bridge is getting past the bottom spark-plug-tube O-ring? Once in the spark-plug tube/chamber, the oil may evaporate, or drain out of the drain hole to the outside of the motor.

[RedRupert]

Originally Posted by charlie264

Compression is good. Did you change the oil rings. What’s the filter like?

Do you mean compression as shown by the compression test, or the leak-down test, or both? I understand the principal of the leak-down test, but don't know enough to know what it really means i.e. what changes when the engine's actually running etc.

Yes, I did change the oil rings.

Which filter?

The air filter - I always replace at the beginning of each season - every 12 - 14,000 km. So it's been old and new over the high oil consumption period.

The oil filter - I change twice a season - every 6 - 7,000 km.

Thanks.

[RedRupert]

Originally Posted by pdxmotorhead

MY humble opinion,, based on my background...

You can't hone Nicasil liners with any tools available to mere mortals.. Usually it ruins the cylinder...

Break in oil should be standard oil, no synthetics at all, preferably a high zinc sulfur break in oil if new cams are involved...

I did the same thing with a motor I built 2 years ago. Started on semi synthetic, and the rings would not seat. I ran straight 30 weight for about 3 days then put the semi back in and voila,, no more oil consumption. (Iron cylinder walls though.. ) But the old Nic barrels on porsches used to wear out two or three sets of pistons and rings before they needed any attention..

Check the vacuum level in the crank case.. It should be close to neutral,, very light suction.

You did valve seals, but how were the guides? Intake valve guides can allow a lot of oil even with a new seal if they are loose.

Just thoughts on it not necessarily answers.. :)

Dave

Thanks. I will answer so that there is a record of what I've done etc.:

I used a Flex-Hone to hone the bores in accordance with the manufacturer's recommendations and instructions. I used the 240 grade Aluminium Oxide version, which produced a nice light and even cross-hatched surface. I used WD40 to lubricate, and ran the tool through the bore with quick strokes for only 20 seconds. It does not look as if I've ruined the cylinder - remember that it drank oil before I honed, as well as after. Flex-Hones should not be used in two-strokes because of the ports.



This is the result:

[charlie264]

Originally Posted by RedRupert

Do you mean compression as shown by the compression test, or the leak-down test, or both? I understand the principal of the leak-down test, but don't know enough to know what it really means i.e. what changes when the engine's actually running etc.

Yes, I did changed the oil rings.

Which filter?

The air filter - I always replace at the beginning of each season - every 12 - 14,000 km. So it's been old and new over the high oil consumption period.

The oil filter - I change twice a season - every 6 - 7,000 km.

Thanks.

Good on both, the compression test is showing 16 bar. I think the lc8 is rated at 11.5:1.

Is there oil on air filter, if you’re not loosing oil down the guides and seals and no oil is being blown on the filter, I would say due to your resent top build its just burning the oil. My lc8 burnt oil till 9k miles, then stopped.

Plug looks fine, not oily and just looks like the engine is running a little rich.

[WRW9751]

Originally Posted by pdxmotorhead

MY humble opinion,, based on my background...

You can't hone Nicasil liners with any tools available to mere mortals.. Usually it ruins the cylinder...

Break in oil should be standard oil, no synthetics at all, preferably a high zinc sulfur break in oil if new cams are involved...

I did the same thing with a motor I built 2 years ago. Started on semi synthetic, and the rings would not seat. I ran straight 30 weight for about 3 days then put the semi back in and voila,, no more oil consumption. (Iron cylinder walls though.. ) But the old Nic barrels on porsches used to wear out two or three sets of pistons and rings before they needed any attention..

Check the vacuum level in the crank case.. It should be close to neutral,, very light suction.

You did valve seals, but how were the guides? Intake valve guides can allow a lot of oil even with a new seal if they are loose.

Just thoughts on it not necessarily answers.. :)

Dave

I'm with Dave he's spot on!

[ragtoplvr]

The leakdown is too high.

You need to run the leak down and listen at the crankcase vent, if it is going by the rings you will hear the air escaping.

Sometimes you have too much blowby and overheat rings, they lose temper. 30 % is too high. When this happens you have to install new ones. You oil will turn black very fast if this is true

Sometimes rings crack, this can be from installation or from excess piston groove wear. Rings can also be put on upside down

Rod

[Boatman]

Originally Posted by WRW9751

I'm with Dave he's spot on!

I agree also. What the OP may have accomplished is makeing the bore even smoother in the end. Thus the same or worse than before.

[Orange Toaster]

Originally Posted by RedRupert

This is my rear plug. Removed after around 5000 km, during high oil consumption:



Is it a plug from a cylinder that's burning too much oil (0.34 litres/1000 km)?

I think the dry black soot around the outside is completely normal. And the rest looks pretty good - maybe it shows the fuel/air ratio to be a bit weak?

But there's a lot of oil on the sealing ring! I've just noticed it. Is it oil? It looks like it.

Maybe the pressurised oil from the cam-bridge is getting past the bottom spark-plug-tube O-ring? Once in the spark-plug tube/chamber, the oil may evaporate, or drain out of the drain hole to the outside of the motor.

Looks pretty normal to me.

/OT

[baloneyskin daddy]

If you think using thicker oil is the answer you're ass backwards as it is harder for the rings to wipe off the thicker oil. Try going to a lighter oil it takes less power to circulate and may even improve gas mileage a little.

[pdxmotorhead]

Yea,, it does not take very long at all to seat rings when everything is right.. 30 weight non detergent oil can be found at marine suppliers sometimes in my country.. as hard and sharp aas nicasil is I'd expect less than 100 miles ot bed the rings, sometimes some mild lugging for 2 or three minutes will help..

On a engine with forged piston and aluminum bore the leakdown needs to be done as soon after stopping as possible, you need the motor warm. The forged pistons loosen way up when cold.. The cosworth I mentioned would go from 30% cold to 5% hot.. :)

Cheers

Dave

[Racer111v]

I can't report on KTM 9xx pistons, but I have seen worn 1st/2nd ring lands causing oil consumption in automotive and motorcycle engines. They also had good compression and moderate leak down.

[walstibsf]

excess crankcase pressure or poor/improper venting can contribute exponentially to oil consumption. As before, you sound like you've got your shit together....but something to consider......


Good luck and laters.....