MS170 Coil pack issue maybe

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MS170 will not start.
It would run for a short while then die & unable to start.
I fitted a chinese equivalent but same issue.
I then bought a repair kit for the Stihl carb that was on it & fine for years.
Just fitted the carb but still no joy.

Sprayed carb cleaner in plug hole but still nothing.
Fitted new plug just in case but no change.
Unable to see if spark was present in the daylight.

I then removed this wire from the coil & first pull it fired / tried to run but died, havent set up carb but i hear it fire as if it wants to go where as before it was just being pulled over & a novice could tell it isnt going to start.

What should i be looking to do now with this wire.
I see the wire removed must be the cut out which when the lever is put to off the metal shroud in that plastic holder then makes contact with the spring piece of wire & kills the engine.
You would think that wire is trapped & making it short out but i dont see it trapped anywhere.

I then though faulty coil but seems to be same issue with the coil i changed it for


My understanding was like this.
Before it would start from cold then when it got hot say 10 minutes of cutting it would die, wait 10 minutes & start it again.
Coil i assumed.

Now coil is fitted im no better off but maybe the coil fitted is just faulty.

How can i now check to confirm my thoughts please
 

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Last edited:
There is a possibility that the HT lead is breaking down between coil and plug when hot. If it's the original plug lead it might be worth renewing it. Other than that and without the 2-stroke in front of me, I'm all out of suggestions.
 
New coil that i replaced is fitted with a new HT lead. So does that rule that out ?
 
The stage im at is black wire off.
Choke is on & ive undone the mixture / tick over screw 1 1/2 turns.
Seems to want to start but no.
So i try with chocke off but the same.

I continue like this by turning screw 1/2 a turn then do the same.

Im currently at 5 turns
 
Unless ignition side is faulty & im wondering how for sure do i rule it out
 
@Scally-Ho
Even though i was seeing no spark i then took your advice.
I started from scratch & removed the newly fitted fuel filter in the tank & first pull it started.

Ive screwed the tick over / mixture screw all the way home & then out 2 turns.
It no starts & runs for say 10 seconds & dies.

Now your advice please.
Do i keep turning the screw 1/2 turn & see if it will run ?

I await your reply Thanks

THIS CARB HAS 1 SCREW & IS LEFT HAND THREAD
 
I'd advise consulting your machine's hand book for setting the correct fuel-air mixture. Run it too lean and you could damage the engine and too rich will cause lumpy running and/or sooting. For continuous smooth running, the correct mixture is critical as is the correct petrol/oil mixture to prevent a 2-stroke seizure or coking up.
 
I understand that, i have no manual.
Im now able to start it & tick over but sometimes when operating the throttle lever it bogs / stalls
 
There is no L / H screw.
It has 1 tick over a few & it’s left hand thread.

It starts & can tick over.
 
I didn't mean the L/H screws this time - just the single Left Hand threaded one.
If I remember correctly it should be screwed right in?
What happens when the machine is ticking over, and you adjust this screw?
John :)
 
Ah ok.
I read it as L & H but LH means tick over.

Seems to tick over ok but i then pull trigger & then it stalls

Yes left hand thread so i screw it clockwise to make it richer / more fuel correct

Turning the screw i see it run fast / slow depending on which way but pulling trigger stalls it.

So this is where im at so not sure how i proceed from scratch to get trigger to not stall it.
 
The original standard MS170 carburettor isn't adjustable, other than the idling RPM.
It's known for being troublesome.......I'd recommend an adjustable carb from an MS270 - or another Amazon replacement.
John :)
 

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