Question about HT 101/131

Apocalypsse

This will probably sound like a stupid question, but my mechanical knowledge ain't so flash and I haven't found something to truely confirm it. Are the HT101 & 131 polesaws 4 stroke or 2 stroke?

Eric Frei

2 stroke

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redmower

2 stroke

few ways to check.

Four strokes nearly always have an oilcap and a sump for engine lube oil. 2/strokes use oil mixed in their fuel to lube the engine.

if you look in thru the carby or muffler in some motors and see the piston/cylinder then you have a two stroke. The air intake is 'direct' to the combustion chamber in two strokes and likewise the burnt gasses come directly out of the ports on the exhaust side of the cylinder. Four strokes use valves to control intake and outlet gasses and have to hold and release at different strokes (up and down) of the piston.

generally two strokes can usually be used at all sorts of positions upside down etc. where as four strokes tend to like flat and level operating conditions so the sump oil stays where the pump can get at it. Honda now have a few small 4 stroke motors in blowers and whipper-snippers that work at angles.

No oil cap is often the fastest clue when you find yourself about to use a new machine, if it isn't already written somewhere on the machine.

Wish more people asked questions like this. Like the bloke who put straight unleaded in my big saw a few weeks ago. (I rather not talk about it anymore because my attitude isn't positive considering the impending cost of the outcome)



R.

Eric Frei

One other key fact is if you run a 4 stroke on 2 stroke .... big deal, but the other way around.

Once my petrol car ran out of fuel, it ran fine on 2 stroke saw gas I had in the back.

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Apocalypsse

Yea I thought so. I've seen the Honda 4 strokes and have seen the sump on them but they aren't on the Stihls. Kept getting confused when some people keep calling it a 4 stroke, maybe they are getting confused because its advertised as '4 cycle'.

Rob Chace

almost all "handheld" petrol equipment is two stroke. or two stroke 4mix etc (still 2stroke)

Apocalypsse

What exactly is '4mix'/'4 cycle', like that big sticker all over the HT101s/131s @ Stihl shops? Some sort of optimisation for 2 stroke engines?

Eric Frei

Here's the low down on it.

STIHL Power tools

Engine has valves, is a 4 stroke but as above it is lubricated by the oil in the fuel.

I still prefer to use my HT75 over any of the other pole saws.

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Apocalypsse

So it is a 4 stroke, but runs on 2 stroke fuel for lubrication. Then what would happen if you run it on straight petrol then? Same result as with 2 strokes?

Eric Frei

Yep, scored bore/piston, stuffed.

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Rob Chace

...thats a bit missleading. You're right that it is 4Stroke, not because it has valves though. but yeah it is fuel lubricated (oil mix) and is 4 stroke - but because it goes:
suck, squeeze, bang, blow (4 stroke you sickos)

some two strokes have valve - power valves/reed valves/rotary power valves etc.


....anyway my explanation isnt any better so here is a video of it (4 cycles and cranckcase lubricated)/fuel lubricated.

I hope that makes sense.

Apocalypsse

It makes perfect sense, just can't resist using that picture. So if you have both fuel and oil lubricating the piston, does it have any effect on the lifespan with petrol added into the lubrication mix? Or do 2 strokes lubricate the same way as in that animation?

EDIT: Just found the '2 Mix' version of the animation, is the blue and green both supposed to be 2 stroke?!

Attached Thumbnails

 

Rob Chace

yes its two stroke.

the colour etc has nothing to do with it.
2 stroke means the piston performs two strokes per fire and 4 stroke is 4 per fire. (i wont say spark, because you can have 2 stroke diesels)

piston move up and down and u get a bang = 2T
piston moves up, down, up and down and you get a bang = 4T



....oh yeah, nice "Daft Wader" pic