Which Chainsaw for Forestry

[Stubby]

2 minutes ago, Joe Newton said:

 Well yeah, that's kind of my point. It wasn't an accusation!

Ah . Understood Joe .  Big sorry ?

[stihlmadasever]

It was decifering the accusitory tone from your statement joe ?

 

[The Technician]

You have missed the point. All 2 strokes have seals. The way it has been done for years was you had the crankshaft, 2 bearings and 2 individual seals. The space between the seals and the bearings was usually 5mm. This 5mm was for cooling. In the 500 series, they put the seal in the bearing. This is why they don't last. I had one last week. A 555. Pulled off the exhaust and score marks. Pulled off the clutch and the seal spring was wrapped around the crankshaft.  It's usually the chain (PTO) side that goes as the shavings and oil get in it and the seal let's go.

[peatff]

2 hours ago, The Technician said:

It's usually the chain (PTO) side that goes as the shavings and oil get in it and the seal let's go.

If the seal is working how do they get in, does it only seal from the inside ? I don't understand that bit.

[The Technician]

The seal is rubber and it touches the crankshaft it also has a coil spring around it. If you get heat from the crankcase or shavings that get to the seal to tear it, you will get an air leak. In the engine, the fuel, oil and air is in an atomised and pressure state. If a seal goes, air gets in and this state collapses, causing lack of lubrication around the piston, rings and cylinder.

[adw]

So the might of Husqvarna have been getting wrong all these years, i will be sure to tell them, should get a laugh.

[spudulike]

I don't know much about two strokes but thought that the scavenging bit happened on the downward stroke and is the releasing of the exhaust gases caused by combustion just after the piston clears the top of the exhaust port and completed by the lowering piston releasing combustion chamber pressure and producing positive pressure in the lower crankcase pushing fuel and air through the transfers and scavenging the exhaust out of the exhaust port!

The heat in the crankcase is surely transferred heat from the piston and cylinder and not the exhaust gases - the only reason you would have exhaust gasses in the crankcase would be blow-by from the rings and piston leaking at combustion.

 

[Ratman]

So the might of Husqvarna have been getting wrong all these years, i will be sure to tell them, should get a laugh.

[emoji51]

[spudulike]

Just now, adw said:

So the might of Husqvarna have been getting wrong all these years, i will be sure to tell them, should get a laugh.

Erm....the last MS260, MS460 and MS660 I did had new seals fitted and .....well I thought they had the seal pushed in to the bearing!

[Joe Newton]

16 minutes ago, spudulike said:

I don't know much about two strokes.

 

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