Stihl KM85 Kombi engine troubles

[chrisj]

A few days ago my KM85 Kombi engine started leaking dark sticky oil. Then near the end of the job yesterday it started making a horrible noise. Sort of roaring. It reminded me of when the exhaust breaks off on the car.

I've stripped it down and can't find where the oil is coming from, the oil had been thrown all over, although it was pretty filthy and horrible behind the flywheel. The 2 issues could be unrelated but it seems a real co-incidence that both came together. Has anyone come across similar before or got any ideas. The machine is 9 years old and doesn't owe me anything. I'll be getting a replacement but if I could fix it to keep as a spare it would be great.

[spudulike]

A few days ago my KM85 Kombi engine started leaking dark sticky oil. Then near the end of the job yesterday it started making a horrible noise. Sort of roaring. It reminded me of when the exhaust breaks off on the car.

I've stripped it down and can't find where the oil is coming from, the oil had been thrown all over, although it was pretty filthy and horrible behind the flywheel. The 2 issues could be unrelated but it seems a real co-incidence that both came together. Has anyone come across similar before or got any ideas. The machine is 9 years old and doesn't owe me anything. I'll be getting a replacement but if I could fix it to keep as a spare it would be great.

 

It is possible the bearing/seal has failed on the flywheel side and the oil is in fact petrol/oil mix coming out of the crankcase.

[chrisj]

That makes sense and is what I suspected. The seal looks ok visually, is there a way of checking it? I've got it on the bench all stripped down with the flywheel off. Also is it an easy fix?

[chrisj]

If it's leaking mix out, is it possible it's leaking air in, accounting for the high / weird reving?

[spudulike]

A pressure check will tell you if it is shot. Other than that, block the inlet and exhaust port, put a plug in and pump air in the impulse line (hopefully it is a separate pipe) and put soapy water around the seal to see if it bubbles.

 

If the impulse is integral to the inlet manifold, you will need to block it and adapt a spark plug.

 

You could fill the crankcase with fuel and see if it leaks out!

[chrisj]

Thanks Spud. I'll have an investigate tomorrow.

[spudulike]

The other thing to leak black oily gunge will be the exhaust if it is running a bit rich or perhaps the upper shaft if it has been greased heavily but if it is coming from behind the flywheel, it sounds like bearings/seal.

 

A bad crank bearing generally makes a rumbling hollow sound and can rattle on a slow idle - pushing the flywheel up and down and side to side should reveal a bit of play if it is shot!

[chrisj]

My first thought was the upper shaft leaking grease but when I dismantled it that side of the flywheel was clean as was the end of the shaft. So I had thought it was likely the seal. The noise it was making was a bit like when it's running low on fuel and revs up, but loads worse, and was a bit intermittent. I checked the H and L screws setting and they're where they should be so it isn't just the tune gone out.

[chrisj]

Oh and I checked the shaft for play while I was dismantling it and there was no sign of any movement what so ever.

[GardenKit]

Oily discharge can only come from unburnt 2 stroke oil. Some after burning of oil takes place in the exhaust before the exhaust gas leaves the machine, but if the exhaust becomes loose or broken the oily residue escapes between the exhaust and the cylinder and can then get pulled around the fan casing by the flywheel. A loose exhaust will of course make a nice throaty roar.

 

So, is the exhaust loose?

Has the mix, or the oil type changed?