I am having issues with my Carburetor and would really appreciate some advice. The initial symptoms were that as I reved the chainsaw, it would bog down. I tried to adjust it, but, as the trigger was pulled, it would bog down. I took it to my local repair specialist who sonic cleaned the carburetor and said that it ran OK. I went to use it and agree that it ran. As soon as it was put under load, it bogged down. At this point, I thought it might need a new Carburetor. The genunine one is over £100 which is near the cost of a new machine. I ordered a cheap one and fitted it. I have tried adjusting it and it actually runs better. I cannot get the adjustment correct. Looking at a number of videos, I have followed the instructions. Both screws fully wound in and then released by one whole turn. The chainsaw starts and revs incredibly fast. At this point, do I release the H or L screw? If running too fast, is it receiving too much fuel from the H screw? Where should the LA screw be in the start up process? I have tried all methods and eventually the chainsaw stops and will not start again. I return the screw to the position it was before it started and again, will not start. By putting the choke on, the chainsaw will start. I am therefore back to where I was before I changed the carb. I have also changed the air filter, fuel filter and spark plug. Is anyone able to offer advice? This is driving me crazy!!
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If you think it's running to fast turn the H screw out whilst holding in the trottle in until you are happy with the speed then adjust the tickover screw so it ticks over ok, the L screw is for throttle response from tick over you should have instant response from the throttle when you flick the trigger turn it in to get desired response.
Your initial symptoms where you said it bogged down would indicate a new fuel filter needed i see you have changed that now, have you changed the gasket for the carb you might have an air leak but as you said you brought a "cheap" carb some would say "what did you exspect a Sthil carb".
If all els fails and you still have original carb buy a repair kit very easy to fit just take pics to guide you
also check the spark arrester gorse in the exhaust exit is clear they can get carboned up and block the exit
Does the 181 have a spark arrester? I was told they didn't and when looked, couldn't see one. Although, I do think it is strange not to have one.
Google 'Steve's small engine saloon' he has a video on carb adjustment.
Link below is also useful
https://www.sgs-engineering.com/help-advice/how-to-tune-a-2-stroke-...
I wonder if it really is the carb thats causing the problem as you've tried another one? When the first carb was "sonic cleaned", was it completely stripped or just dropped in the tank. It should have been completely dismantled, the diaphragm, metering valve membrane etc replaced Blow through the whole carb body with carb cleaner and then ideally, compressed air.
Also worth checking out Stihl chainsaw blog on E10 petrol .
Now only using my Petrol Stihl gear occasionally and feel their advice on not storing fuel containing E10 petrol for more than 30 days is relevant on manual adjustable carbs .
Changing fuel mix is the simplest starting point .