Stihl MS170...won't start?

[wisecobandit]

I've not seen those e.bay carbs before. They are copy parts, not Zama. Are they any good?

 

Scarily they are not bad and hold tune etc very well as well as giving you the option to tune the saw using h and l screws unlike the o.e carb. Ive got one on my 170 use for hedge laying etc and never had to retune it.

 

The biggest issue tho is obviously as the oe carb doesn't have l or h screws the air filter gets in the way of tuning the aftermarket one so needs a bit of a mod to get a screwdriver in (and drill a hole in the top cover) or bolt the carb on leaving the airfilter off and tune then refit airfilter albeit you may have to take the filter off a couple times to get it 100%

They are a copy as you say but the diaphragms etc are interchangeable.

[Dan Forsh]

I'm no pro by any means but, two strokes are simple creatures. Does it have compression? You said it has spark. That only leaves fuel. Assuming it does have compression and, It does not need to have the amount of compression it had when it come from the factory but if when you pull on it there is little to no resistance... junk it. After that its just reed valves and carb. If it has the first two compression and spark I normally just drop some fuel in it. If it fires I know my carb is bad or clogged. If it don't its the reeds that simple...

 

I know you lads regard yourselves as A team p*** takers, but I've got to agree that there's a certain misplaced cockiness about this post that deserved it.

[spudulike]

I know you lads regard yourselves as A team p*** takers, but I've got to agree that there's a certain misplaced cockiness about this post that deserved it.

 

It has to be done and just hope the poster has the good humour to laugh with us and take the piss back!

 

Something tells me he grew up on 1970/80s motorbikes - FS1e and RD200/250 etc probably - chainsaw problems can be simple but can also often be very involved and defy comprehension - gotta be pretty smart to call everything easy - only Rich is that smart:001_tt2::lol:

[GardenKit]

Sorry if my comment may have been construed as p**s taking. It was not really aimed at jgreene, just making a bit of humour. Our 'grade A' pisstaking is normally aimed only at the frequent posters we know well

 

Anyway, welcome to the forum mr jgreene33, good advice is always welcome and there is a lot to be learned here, by all of us.

 

It is however important to only offer factual and relevant advice.

[Rich2484]

It has to be done and just hope the poster has the good humour to laugh with us and take the piss back!

 

Something tells me he grew up on 1970/80s motorbikes - FS1e and RD200/250 etc probably - chainsaw problems can be simple but can also often be very involved and defy comprehension - gotta be pretty smart to call everything easy - only Rich is that smart:001_tt2::lol:

 

Thanks spud. I've been called many many many things in the past. Smart is going in the book tho. :lol::lol::lol:

 

Sorry but as it seems with most threads on the tech side of things I'm going to do a slight derail.

 

Mate has a two stroke motorbike, it floods very easily and starting is a bugger, I did read about the reed valves but I'm unsure to be honest. Anyway what do you know about two stroke bikes with reed valves, sorry will get the make and model and let you know what it actually is, just fishing to see what you know spud?

 

Yeah two strokes can be very easy but can really mess you up. I got this first hand with what has to be the most finicky, confusing, smallest, and excellent saw of all time. Can anyone guess the saw??? Spud you are not allowed to answer this question :001_tt2:

[spudulike]

Thanks spud. I've been called many many many things in the past. Smart is going in the book tho. :lol::lol::lol:

 

Sorry but as it seems with most threads on the tech side of things I'm going to do a slight derail.

 

Mate has a two stroke motorbike, it floods very easily and starting is a bugger, I did read about the reed valves but I'm unsure to be honest. Anyway what do you know about two stroke bikes with reed valves, sorry will get the make and model and let you know what it actually is, just fishing to see what you know spud?

 

Yeah two strokes can be very easy but can really mess you up. I got this first hand with what has to be the most finicky, confusing, smallest, and excellent saw of all time. Can anyone guess the saw??? Spud you are not allowed to answer this question :001_tt2:

 

With reed valves, the carb is attached to the crankcase and not the cylinder, it relies on the flexing of the reeds to pull fuel vapour in to the crankcase and the reeds to seal the crankcase under crank pressure.

 

The other common method of controlling the inlet fuel air vapour was rotary valve as previously mentioned - this was quite a neat solution of having a rotary disk with an inlet cut out that rotates in time with the crank.

 

On our modern saws, the inlet of fuel vapour and air is controled by the piston and the inlet port giving uninterfered inlet but has limited duration.

 

The advantages of reed valves are that they are not dependant on port timing so opening duration isn't an issue however the reeds do block the inlet port and therefore are not as efficient as port timing - a reed valve machine will rev a lot lower and make full power at lower revs than it's piston ported counterpart.

 

Issues - forming a good seal and the reeds cracking - check this first!

 

If the carb is running rich then in a slide valve carb that most bikes would have, you would lower the slide needle by moving the circlip on the needle up a notch toward the fat end and not the needle end.

 

You should check this but not deviate from the manufacturers spec.

 

One last thing to check - the float height in the carb and if the needle valve (like our saws needle valve) NOT the throttle needle is sealing properly as if it leaks, fuel will raise in the carb and eventually flood the engine.

 

 

Any good:thumbup:

[Rich2484]

Cheers spud. I havnt looked into it yet. But after trying to start a very strong smell of petrol from exhaust. The bike hates choke.

 

But also need high revs to get the power to pull away. It's only a small engine. But sonds very strange to me. Well get the make and model.

[Dan Forsh]

Sorry if my comment may have been construed as p**s taking. It was not really aimed at jgreene, just making a bit of humour.

 

My comment wasn't really aimed at you either; yours was milder than Spud's, but both were deserved IMO.

 

Yeah two strokes can be very easy but can really mess you up. I got this first hand with what has to be the most finicky, confusing, smallest, and excellent saw of all time. Can anyone guess the saw??? Spud you are not allowed to answer this question :001_tt2:

 

I'm gonna guess at the MS200T based only on my limited experience of them:001_smile:

[Stubby]

Mmm 1929 Scott squirrell 600cc 2 stroke with acetylene lamps ..Oh no its a saw . Err Stihl contra ?

[spudulike]

Mmm 1929 Scott squirrell 600cc 2 stroke with acetylene lamps ..Oh no its a saw . Err Stihl contra ?

 

Scott, now there's a bike ahead of its time