Please help - high oil consumption

I wonder if anyone can help diagnose my high(?) oil consumption.

My bike is a 2004 950 with 90,000 km (about 56,000 miles).

During it's early life, oil consumption was acceptable - I mean, it needed topping up with <1 litre between 6-7000 km oil changes. So about 2 litres per 14,000 km (8700 mile) season. (0.14 litres/1000 km).

Over time the oil consumption became worse: 4 litres over 12,000 km, so 1 litre/3000 km (0.34 litres/1000 km).

At 74,000 km, I had to strip the engine in order to replace the selector drum. While the engine was apart I replaced the (serviceable) piston rings and honed the bores lightly. After honing the ring end-gaps were all around <0.32 mm (limit 0.5 mm). I did not have the correct tools to measure the bore and piston accurately.

I also changed the oil seal in the ignition casing (the balancer shaft oil seal).

I ran-in on semi-synthetic oil for over 1500 km on twisty roads not being too gentle - using plenty of acceleration and engine breaking - but oil consumption remains high.

16,000 km after the rebuild, I measured compression and found 16.5 BAR (240 PSI). And carried out a leak-down test and found around 30% leakage, front and rear.

KTM state:
0.3 - 0.6 litres/1000 km: normal.
>1.0 litres/1000 km: there MUST be a serious technical defect!

My bike is ridden hard, but 0.34 litres/1000 km does seem a bit steep! Is it, despite what KTM say?

Looking at the leak-down and compression test results, could it be that the bore/piston/rings are at fault, or should I be look for another reason for the oil loss?

Any info will be gratefully received.

Thank you.

Do you have oil in your front carb? The balance shaft seal on the left side if the bike is a known culprit.

Yes, I did that - see 6th paragraph in my first post.

Compression seems ok. Maybe you need some more time with non syn oil to get the oil rings to take a set.

How are the valve seals, any smoke?

You are on the lower end of acceptable oil use. KTM might be using a light tension oil control ring???

-John

I've covered a further 12,000-odd km using fully synthetic oil since the post rebuild 1500 on semi synthetic. Maybe it's a bit late to go back to semi or non-synthetic?

I replaced the valve-stem oil seals when I rebuilt the engine.

Sometimes I'm told there's a puff of smoke on overrun. But could that be enough to burn so much oil?

Thanks.

In my opinion (I am no expert) you should be looking at valve guides and seats.

I lapped the valves when I rebuilt the engine, also they were not leaking when I carried out the leak-down test.

The valve guides were checked and were OK when I rebuilt the engine.

If you no longer have an oily front carb, you know the valves are good, and she is not leaving a puddle when stopped, you are kind of down to cylinder walls and ring seating in my mind. I know that Pyndon had a delamination of nicacil in a cylinder on his bike that he wrote about in his My KTM 950 Story thread. That's all I can think of. You might PM Pyndon to see if he has any other thoughts.

When I rebuilt the engine, I checked the Nikasil surface of the cylinders, and found it to be in very good condition.

The breather pipe from the balancer shaft, I have lead into a catch-bottle so that I can monitor oil exhaled. There is nothing to speak of in the bottle.

Well, no valve leak per your thoughts, and no balancer shaft seal issues, and nothing leaking on the ground. I'm assuming it's not pumping oil out of the radiator overflow.

Then you are down to ring seating, right? Maybe your symptoms relate to the honing. Dunno. Here's a related discussion: http://www.thumpertalk.com/topic/294800-honing-nikasil/

The coolant is clean and there is no abnormal activity concerning the cooling system.

My symptoms were present before the new rings and honing - it's why I installed new rings and honed.

I can't say that my oil consumption is down to ring seating - it's why I'm posting. To me it looks not, as the leak-down test looks normal.

There may be a cause that is pretty unique to this engine - like the balancer shaft seal, for example.

Thanks for the link.

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

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

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

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.

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.

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

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.

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.