Stihl Hedge Trimmer Problem

[Steven P]

Good evening, and appologies if this has all been asked before recently

 

I got a second hand Stihl Hedgetrimmer (HS61, if it makes much difference - the advice I am looking for will be the same I guess for all 2 stroke engines)

 

Came as sold as seen, and they couldn't get it working after it had been sat in the garage for a while. Silly me reckons I can do better and failing that my local dealer will take a look for a few ££. So far I can't do better.

 

So:

- The spark plug sparks OK and looks new (it might have been replaced recently)

- There is fuel in it (ruling out the obvious, and the fuel is fairly new, my chainsaw works well with it still)

- Trying to start the engine and it makes the purring noise as it moves (not sure if that is the technical name for the noise it should make?) - nothing unusual. A decent amount of resistance to the pull cord so I guess compression in the cyclinder is OK

- After turning the engine over the spark plug is wetted with petrol so I guess the fuel lines are OK and the carb isn't blocked?

- The choke works OK, opens and closes

 

 

- The mesh over the exhaust outlet was pretty black when I got it, I've cleaned that up

- I need new air filters, trying to start the engine with no air filter (in a clean environment) and nothing

- After a while pulling to start it, petrol comes out of the exhaust, guessing the engine is flooded by then?

- The cutting blade is off ther machine (just in case that and the clutch was jammed)(Oh, clutch isn't jammed on)

- It has run on twice, once at 11:00 last night, and I turned it off after a couple of seconds thinking better - The Boss and The Boys were in bed upstairs (OK, I know I should have been in the garage but I had a film and the fire on in the living room). And again for a couple of seconds today before it died

 

So as far as I can tell, fuel is getting into the cylinder, the piston moves freely, air is getting in, there is a spark, and some compression.

 

Where am I going wrong? Not thinking it is too serious to fix

 

 

thanks in advance for any help

[Stubby]

Are you sure its sparking under compression ? Sometimes if the coil is tired it will spark in fresh air but not under compression . Is the fly wheel gap to the coil correct ? Is the flywheel key sheered putting it out of time ? How good is that bit of compression ? might not be enough . Check piston through exhaust port for scoring . Just a few things to look at .

[Steven P]

Thanks Stubby,

 

So tonight I'll have a look at the piston / cylinder - that looks easy to check for scoring, half a dozen bolts. Can check to see if the rest looks in tact as well while I have the spanners out again

 

Flywheel - I'll assume for now that the flywheel gap to the coil hasn't altered and should be correct?

 

So - and this is where I have to admit my lack of knowledge - checking the spark while the plug is in the cylinder - I guess there would be a meter to do that and I guess that you cannot do it with a bog stadard multimeter - is there a DIY way of doing this? (lets assume that I have just been watching the fireworks and the shops are closed now to buy new gadgets)

 

Similarly - and again a lack of knowledge, is there a DIY way to check compression?

 

 

Thanks - got some more things to look at tonight

[Steven P]

Just a quick update...

So tonight I had the exhaust assemble off and looked in the cylinder - all looks good, smooth, and as it should be (while I was in there the exhaust got a good clean too). So I guess the piston and cylinder is OK. Turning the engine over and the piston moves smoothly and no sticking poiints. All good there.

 

Took the starter assembly off and some of the housing to see the flywheel - again all looked good, looks to turn as it should, no wobbles etc

 

Also took the air intake housing off to clean lots of tree out from behind it

 

So put a bit of fuel in the direct cylinder (saw than on another site), with the exhaust and air intake cover (and filters) off, a few pulls and it coughed - which I didn't expect. Tried again, skinned my finger (see my next post, first aid for daft sods playing with hdgetrimmers), few pulls and a cough.

 

Did the same by pouring fuel direct in through the carb. again, a few pulls then a single cough

 

So thats where I got to...

 

I guess it is sparking under compression (at least some of the time) and there is some compression there some of the time.

 

Coughing - it took a few pulls and didn;t do it every time

 

So any other clues? I am thinking that the fuel line might need some attention but not sure what else to look for still

 

thanks again for any advice

[farmer rod]

you seem to have a good grasp on what to look out for, and Im hesitant to suggest the very obvious, but if a Stihl fires , then it is time to move the lever to the choke off position, and pull again. Appologies if you know this already

[Stubby]

Still could be that the flywheel key has sheered . The fly wheel will still spin and make a spark but it may have shifted on the shaft putting it out of time . It will still be " stuck " on the taper but in the wrong position slightly . Not saying it is this for sure but you need to pull it off and check .

[Steven P]

Not made a schoolboy error yet and forgot to change choke - the trimmer only fires once - usually it would fire a few times before I would want to do that, thanks for the suggestion.

 

 

Back to the flywheel - I'll have a look at that, thanks. I didn' get chance to look at it today. It needs a bit more dismantelling to get at that but will give it a go. Just a bit sceptiocal - I know its an older model but it can't really have had a tough life so I am dubious if parts could ahve sheered -but gues since you menti0on it it must happen fairly often.

[Steven P]

A quick update -I got the engine running this morning. I think it was the carb, had that off and cleaned up, had the diaphragm cover off to check that moved OK, and set the high, low and idle screws to 1 1/2 turns from being fully closed. Somethin I should have done when I got it. Thanks again for the advice

[Stubby]

A quick update -I got the engine running this morning. I think it was the carb, had that off and cleaned up, had the diaphragm cover off to check that moved OK, and set the high, low and idle screws to 1 1/2 turns from being fully closed. Somethin I should have done when I got it. Thanks again for the advice

 

Nice one . Well done .