Oil Consumption issue

My 850 has decided to burn oil at a pretty good rate. I think it's come on gradually in the last 300-400 miles, but it has developed into laying down nice blue smoke trails.

Some background: A full re-build was completed 1000 miles ago. The bike runs perfectly and has good compression. It has a PCV valve installed in the breather line.

But, I have noted a recent oil leak near the tach drive that seems odd. It's a new leak.

Just wondering if crankcase pressure gets high enough, could that cause the oil consumption?

If the PCV valve was plugged for any reason, could that cause the pressure issue?

Otherwise the head & jugs are coming off shortly for a look-see.
Cheers!
Stephen

1. You should be able to feel the air at the breather tube in side the oil tank at the neck where the line comes in.

2. Drain your sump to see how much oil you have in there before AND after a ride.

3. On the other side of the neck you should see oil returning to the tank under that deflector flap over the return orifice.

4. Make sure the seals are in place over the intake valve guides.

5. Get a screw in cylinder pressure gauge and check cylinder pressure. Harbor Freight. Pull the opposite plug holding the throttle open and kicking it over hard and fast 6 to 8 times.

Is it one side or both sides blowing smoke?

Main reason for using oil after a rebuild is cylinders getting glazed, and oil being able to make its way past the oil control rings. Glazing comes about due either to inappropriate oil being used, or not enough load being put on the rebuilt motor soon enough.

If the problem is to do with glazed cylinders, then generally the smoke will be worse when accelerating. On the other hand if it smokes on a closed throttle, then in most cases problem will be related to valves or guides.

There are ways to overcome glazed cylinders without strip down, but strip down and honing affected cylinders and rebuilding with new rings will generally be required.

If the bike ran clean up to about 1,000 miles it doesn't sound like glazed cylinders.
If smoke only on one side I'd look at intake valve seal.
I finally figured out my smoke on right side. A split oil valve stem oil seal on that side intake valve.
I too initially thought I'd not prepped or broke in rings properly.
I'll find out for sure tomorrow since I'm just putting head back on.

Bob

I've had the intake valve seal come off twice. Both times it put out serious smoke on one side only when opening the throttle after decelleration or idling a minute or two (I have a video which I'll try and post a link to). Others have suggested this is due to a vaccuum being drawn on the intake when the throttles shut, which makes sense to me.

I've also had a serious problem with oil migrating to the primary if the bike wet sumps *at all*. I'm getting ready to tear into the primary to check out the crank seal and possibly apply locktite or some other sealant to the studs. If you have some serious oil loss may be worth checking if your primary is overfull... only takes a few seconds...

What sort of PCV do you have fitted? My ball check 'motormite' style quit after about 100-200 miles. Very obvious it quit because oil leaks showed up *everywhere*. Replaced with the XS style reed valve, much happier with that and a great $20 upgrade. It squeaks when I kick the bike over, so if every plugged it would be obvious.

Ludwig and others contribute a good discussion on possible causes of oil consumption and smoking in this thread, and ways to troubleshoot the cause:

post51269.html?hilit=ludwig oil head#p51269

Ludwig also provided an excellent tutorial on replacing an inlet valve seal (if you determine that to be the culprit) without removing the head here:

post76177.html?hilit=ludwig oil head#p76177

Cheers,

- HJ

Here is the video of my bike smoking out the left exhaust for people to compare to. Root cause was a intake valve seal that had come loose and was riding on the shaft of the valve.

http://www.youtube.com/watch?v=IKtaS3ofDZo

Cheers,

- HJ

Hungry J0e said:

Here is the video of my bike smoking out the left exhaust for people to compare to. Root cause was a intake valve seal that had come loose and was riding on the shaft of the valve.

[video]http://www.youtube.com/watch?v=IKtaS3ofDZo[/video]

Cheers,

- HJ

Click to expand...

Mine smokes just a tiny bit on warmup. But nothing like that.

- HJ[/quote]

Mine smokes just a tiny bit on warmup. But nothing like that.[/quote]

Dave

I did run my bike today and the new valve seal has stopped smoke from right side.
However my bike previuosly had to be warmed before it happened.

If yours smokes during warmup its symptoms don't match what mine were.

Bob

Here is an update on my oil burning issue: Keep in mind this re-build had 800 miles on it.

I pulled the head & jugs to discover the 2 compression rings have acquired sharp edges, much like burnishing a woodworking scraper. This must have come from rubbing against the equally hard surface of the cylinder. My guess is the rings purchased from Britcycle are aftermarket (I did not know this), as compared to UK made rings. I never questioned it but the were $50 a set compared to Walridge $99 a set.

The right side was worse than the left. I believe the rolled edge the rigs acquired prevented them from turning in the ring lands of the piston. The result was a scratching in the right cylinder that permitted oil consumption. The right piston had a lot of carbon residue on top.

Anyway, I have honed out the scratches and we're replacing the rings with UK quality rings from Walridge. I shall update you later on this.

Stephen

Stephen

Take care to ensure that the two compression rings have enough end gap when squared in the cylinder with a piston and measured at the top, middle and bottom of the stroke--if the ring ends abut the entire ring will rapidly abrade and never seat satisfactorily--good luck


Tim Kraakevik
kraakevik@voyager.net

kraakevik said:

Stephen

Take care to ensure that the two compression rings have enough end gap when squared in the cylinder with a piston and measured at the top, middle and bottom of the stroke--if the ring ends abut the entire ring will rapidly abrade and never seat satisfactorily--good luck


Tim Kraakevik
kraakevik@voyager.net

Click to expand...

Sounds like this may have been the issue in the first place. Lesson? Ring gap, not enough is much worse than a little too much.

pvisseriii said:

kraakevik said:

Stephen

Take care to ensure that the two compression rings have enough end gap when squared in the cylinder with a piston and measured at the top, middle and bottom of the stroke--if the ring ends abut the entire ring will rapidly abrade and never seat satisfactorily--good luck


Tim Kraakevik
kraakevik@voyager.net

Click to expand...

Sounds like this may have been the issue in the first place. Lesson? Ring gap, not enough is much worse than a little too much.

Click to expand...

I agree with this. Having said which, I set mine at the very bottom of the acceptable range (as small as possible) and never have had any issues.

Edit: Per my notes, 10 thou gap on the upper ring, 12 thou on the second ring. Failed to note what I set the oil ring gap at.

All rings are after market, so any good brand shouldn't make any differrence.
Are the ends of the rings shiny ? ,no end gap.
Does your air cleaner seal ?
Fuel wash will burnish rings real quick leaving a raised razor sharp edge.
## I honed the scratches out## to coarse honing followed by insufficent cleaning is a very common cause.
If thoose terrible rubber valve stem seals come off they act like a pump forcing oil down the guides.
Good luck

Folks,
What about dust getting into the cylinders? Would that cause the slight wear in the bore enough to create significant oil consumption?

I have never oiled the foam element in the air filter box. Was over a 3-4 mile section of dirt road, not that long before I began to notice oil smoke.

What do you think? Could that be enough to do it?
Stephen

I have to ride on a gravel road for 1 mile to get to the paved road, so that's 2 miles every trip. Unless you are really stirring up a lot of dust, I don't think it would be an issue. I haven't had any smoking or oil burning that I know of since my rebuild last fall, but so far only 200 miles on it.

Dave
69S

If you live on dry dusty gravle roads , and run no air cleaners lik many bikes did in the 60s ,
20 to maybe 25.000 mile life with hard use from dust inhilation . Fancy air filtration will
double or triple cylinder wear time yo overhaul . Easy .

Putting a finger in the carb intake after a ride will show why .Fin dust overlay on everything
outsid too . . .

I really did not think one 5 mile run on a dirt section would do much damage.