Smokey 582

[Spurwing]

On my last flight - 4.5 hours I noticed that my oil useage seemed high and saw a lot of smoke as I accelerated after a fairly long idling descent - thought it was simply a build up of oil on the descent and did not pay any real atytention as all the operating parameters and temperatures were correct. Now after trailering my trike home and starting it I get a very heavy blue smoke.

This smoke continued for some time and did not diminish so I switched engine off concerned that continued operation could do some real damage.
Engine sounds fine but the smoke is not normal.

Any suggestions as to what the cause could be and how to check it - engine is a grey top with about 280 hours.

Thanks

[ZU-CDW - Shark]

Hi Spurwing,
The only reason why a 2 stroke would smoke excessively and continuously while all the parameters e.g. EGT and Water temp is fine and sounds healthy is that the oil mixture is to rich. If you have an auto oil lube system it could be that it is faulty. Remove it and pre-mix your fuel 1:50 and check it out.
If you already use pre-mix and all sounds well and all parameters are fine then I have no other advise. Also ensure that the choke is off.

I have a Rotax 618 and use pre-mix and it only has visible smoke during warm-up.

Hope you are successful in the fault finding mission.

Regards

[Morph]

Do you have EGT gauges? if yes were you running very cool on the long decent?

I have had a situation where I have had extended decent, 8500ft to 1500ft in the Franschoek Valley. On landing back at my airfield I took the plugs out and they were pretty gunged up. I ran very rich over the decent. You can see it on your EGT's. if cool, very rich. Move the throttle a bit and try find an rpm not too rich and not lean either.

Try testing with premix, but I think check your plugs, clean or replace, then clean your carbs out. You might have sticking needles, blocked jets etc

[justin.schoeman]

Not sure of the crankcase construction on the Rotax engines. On some 2 strokes, with the throttle closed, it generates a very low pressure in the crank case, and can suck oil in through the crank seals from the gearbox.

If it is sucking oil through the crank seals, it often means the crank main bearings are on their way out.

[AndyG]

I go with Morph on this one. Sounds like it ran quite rich on your long descent. Do the checks and if no joy then do a premix test as suggested.

Let us know of the outcome. Will be interesting to know.

Cheers,

[Miskiet]

Rotax connot suck oil from gearbox - there is an air space with a rubber damper in between....

Is your waterpump/rotary valve oil reservoir keeping it's level? If its not this is where the oil may come from. (Highly unlikely that the crank seals are leaking so much oil....)

Far more likely is that you are running a little too much oil due to a failure of the autolube pump cable/connections (cable adjuster came loose or is not properly adjusted). I'm not that familiar with the system as we all believe pre-mixing is best - If the cable fails does the pump revert to 50:1 ratio or richer? The extra oil is probably accumulating in the engine and being burned at high revs.

[Spurwing]

Hi guys

Thanks for the info - i am suprised that no one has mentioned rings going as that is what I thought of straight away and is the reason why I am hesitant to continue running the engine- am I on the wrong track here completely or could that also be a possible cause

[justin.schoeman]

The crank case of a 2 stroke does not contain oil. Bad rings make (virtually) no difference to the smoke out of a 2 stroke...

[Morph]

Hi guys

Thanks for the info - i am suprised that no one has mentioned rings going as that is what I thought of straight away and is the reason why I am hesitant to continue running the engine- am I on the wrong track here completely or could that also be a possible cause

Take the exhaust manifold off and have a look. The sleeves should be nice and smooth with a cross-hatching (i.e. diamond) shape pattern on it. If there are any vertical grooves, deep scratches etc then you have serious problems. Look at the pistons. Expect the top of the piston to be black and there will be two rings near the top. Use a piece of wood like a chopstick or the plastic handle of a screw driver and push against the rings. There should be movement, very little, but movement. If you cant see any movement look carefully at the rings and look for oil pushing out from in between them as you push against them. If there is none look at the sides of the piston walls. If they are burned black below the rings then you are getting blow-by, caused by sticky rings. This will require a decoke. And that is another story

[BOATCH]

Hi I do not agree with miskiet ,i had a 503 that also started smoking and i thought it was the mixture and all sorts of other things. One morning i had a noise on the engine and walla the gearbox locked up , once on the ground i checked the oil in the gearbox and it was bone dry.The oil seal between the gearbox and the engine had gone and the oil seaped out on no1 cyl and it burns the oil and you do not see any oil leaks on the outside. MONITOR THE GEARBOX OIL .

[Miskiet]

Sorry Boatch - i assumed he had an E-box

[SoLo]

Burning Oil = Blue Smoke
Rich Mixture = Black Smoke

[BOATCH]

Have the motor running till it is hot and then switch off the motor and remove the plugs and see if they burn the same. Blue smoke is oil burning.