Mt trusty saw has decided to start playing up. It started bogging when I opened the throttle on it so naturally assumed it had started to run a bit rich or possibly lean (I find it hard to tell the difference between a rich bog and a lean bog).

So bought a new plug (old one wasn’t too bad – not rich, decent tan colour) and stripped and cleaned the carb. All looked okay in there but it had picked up some crap so completely cleaned it, checked fuel lines etc. Re-built it and still the same. Idles reasonably ok but as soon as I touch the throttle it bogs and I have to carefully try and get it through the mid-range of its revs until its on the very top end where it seems to run ok in the very top of its revs.

Genrally speaking though, it’s very temperamental now. Hard to start, difficult to keep on tickover and near impossible to get it into some power.

Thoughts?

you dont say what saw is it ….

although the plug looks good – what colour spark you getting ?

look at the lead to the plug that and tha air filter would be my first call

next would be an engine rebuild with new rings

Is the choke stuck on ?

Ive had this on my MS230.
Never really found the solution so took it into a local specialist and he seems to have the magic touch tuning it again. But although he cleaned the carb, he said that the needles can get worn over time (and mine is fairly old) so maybe time for a new carb.

will it rev better if you leave choke on nearly fully closed? had this with a strimmer & as stoner says the needles wear after time, bought a carb rebuild kit off ebay stripped & replaced all gaskets & main needle job sorted.also the butterfly diaphram in the carb can split so it doesnt pull fuel into carb correctly & that can cause start/run probs.

could be base gasket, if it’s a diaphram carb,which unless it’s ancient it will be..the drop in vacuum stops the fuel from being pumped in the correct quantity.of course,it could be one of the crank oil seals,giving the same symptoms.
have you messed with the high rev limit screw ? this will also give same symptoms…
etc… 😉

My cheap as chips hedge trimmer was like this. Fresh fuel (Shell V-power for its cleaning additives) and 10 minutes idling sorted it. Still not as good a motor as my Stihl brushcutter…

Check the basics first – new batch of fuel that has been correctly mixed, clean the air filter and new plug.
If it’s still duff see if you can find the basic carb settings on t’interweb and adjust it to that.
If still no good then the carb needs a clean as fuel can go off and gum up the jets. You can either do this yourself or take it to a specialist.
For example I got my trials bike out on Saturday after not riding it for about 4 months but it would only run on choke. Removed the carb, blew out all the jets and one of them was gummed up – needed a bit of wire from a wire brush to clean it out. Reassembled and was immediately fixed.

My cheapie strimmer got like that. Would only run on part choke and throttling was a bit wooly. A good dose of carb cleaner and a bit of fiddling and it’s back to normal now.