smoky 2 stroke

[norsa]

Acquired a husky hedge trimmer last year with a smashed gearbox casing. Rebuilt it and had a do with it today. More blue smoke on full chat than my strimmer and chain saws, knock at full chat (only) and black oil from exhaust. 50:1 mix....Ring??
Nick.

 

[pedrobedro]

Oil in crankcase probably? Is it knocking on full chat or running rich and four stroking ?

 

[norsa]

I'm a bodywork man not a mechanic. 4 stroking?

 

[Jim_gsxr1000]

You would be surprised at the amount of idiots that think 50:1 is 50MLof oil to 1L of petrol

 

[norsa]

Charmed im sure. I know how to mix 2 stroke.

 

[Jim_gsxr1000]

I wasent having a go mate, just assumed it was full of old fuel from the previous owner, I had the same issue with a jetski, was smokey as hell on the first tank previous owner had been mixing the fuel and oil way too rich!

 

[the snooper]

first thing is does it smell like 2 stroke oil being burnt ?
don't know how its built could gearbox oil be getting into crank case

 

[PTvor]

Air filter? If it's really grotty, that can upset the mixture.

Carburettor completely out of adjustment, because the previous owner fiddled with it? Modern carbs tend to be set and sealed at the factory.

 

[normspanners]

most hedge trimmers have greased gear boxes so not likely to be that but I have known some bikes, the oil seals are fitted the wrong way intentionally, so that it stops the oil been drawn in from the gearbox, my crosser for one I had to do that coz it was burning the gearbox oil but I would doubt it was on this as it is probably greased. it sounds to me like an incorrect mix for some reason coz where else can the oil come from?

 

[the snooper]

I agree that's why I mentioned the gearbox oil, if its grease in the box then the oil can only be in the fuel

 

[norsa]

Jim. I accept badly worded mate. No it was on my chainsaw mix. Snooper. Smells like 2 but rich. Direct drive to g,box at the cutting head. PT. Didn't check filter but it fires up readilly from cold and needs choke. I'll have a fiddle with the fast jet. Norm. Exactly, how can oil emit from the exhaust when its a dry crankcase. So not ring(s)?

 

[the snooper]

it wont be the carb setting either, a rich mixture gives black smoke and would probably run bad, also the fact it needs choke suggests its not that rich

 

[norsa]

Don't suppose it would object to being used 90' from upright would it?

 

[the snooper]

with a 2 stroke unless it has oil other then 2 stroke seeping in then it has to be in the petrol, its it really bad ? and it wont do any damage you could try a fresh mix just incase you made a mistake when mixing and didn't realise

 

[PTvor]

It should run in any position because it has a dry crankcase and diaphragm carburetor.

Oil in the crankcase could be from the previous owner mixing the 2 stroke at 16:1 like he used to for his BSA Bantam, except the oil he was using was supposed to be mixed at 50:1 and it's now got 1/2" depth of two stroke oil in there.

One of my neighbours has a hedge trimmer which churns out blue smoke because regardless what it says on the bottle, he mixes at 25:1.

I agree with Snooper, if you are having to use choke it sounds as if the mixture screws are set too lean if anything.

I can't see why bad rings would cause this.

 

[the snooper]

bad rings would only lose compression not burn oil, there is non to burn

 

[Lawnmowerboy]

There is only so much oil going in so that is all that can be burnt. Could be carbon in the exhaust burning off?

 

[the snooper]

There is only so much oil going in so that is all that can be burnt. Could be carbon in the exhaust burning off?

the exhaust could be full of oil burning off

 

[normspanners]

yeh good thinking on the carboned oil already in the exhaust can take a lot of burning off a little oil goes a lonnnng way!

 

[normspanners]

Norsa I now realise that you are not quite aware of how a two stroke works, when you asked about the rings.
they work by drawing the air ,fuel and oil mix into the crankcase first, where the oil is freed from the the fuel and lubricates the crankshaft and the cylinder under the piston, where it is then, as the piston is driven down by the last power stroke, it is compressed and forced up into the combustion chamber, ie on top of the piston by ports in the cylinder that are uncovered by the piston , it sort of turbo charges its self but it is called two stroke because it only uses two strokes of the piston instead of most petrols or diesels that are four strokes but have a sump full of oil under the piston. to lubricate things.