Strimmer question - what to do next?

[CelticRambler]

A couple of months ago, my strimmer suddenly decided it didn't like hard work. It'd start OK, run happily at "idle" for as long as I let it, but would cut out when revved to full strimming speed. This happened in the middle of an otherwise unexceptional session.

So I stripped down the carb, cleaned it, replaced some of the fuel line (which had cracked), reassembled everything. No difference.

Was pressed for time, so ordered a new carb, which didn't arrive quick enough for me to do the replacement myself, but SonNo.1 fitted it and reported that the problem was fixed. He used the machine for a full day, ran it dry at the end of the work, and put it away.

I went to use it on Friday - same problem as before. Thought it might have been the fuel (two-month-old SP95-E10) so got some fresh SP98 and made up a perfect 2% mixture. Better, but still not right. I was able to do the yesterday's strimming with the trigger locked in the "start-up" position, but this was only light work (little more than brushing fallen leaves off the grass); and when I tried a full rev at the end of the session, I got a few seconds of high speed, then sputtering and cut out.

Having replaced the carb and the fuel, what's the next thing to look at?

[490808]

My diagnosis would be that the carb isn't providing enough fuel. I had the same issue with a cheap strimmer and a new carb off Amazon fixed it.

I'd check the high (H) screw and open it out a bit, most would 3/4 to 1 3/4 of a turn out from being gently seated. Although as I'm sure you know its not always that simple and the low (L) screw may also need adjustment. I tend to get max revs then open out the high screw a little more till the revs drop slightly so it gets more fuel (and lubricant) rather than running really lean (iirc that info used to be in the Stihl manuals for most of their 2 Strokes).

BUT I've just been persevering with a chainsaw behaving somewhat similarly and a new plug fixed the main problem but also needed a slight retune. A plug can work OK at low revs but fail at high, same with the ht lead.

Other seemingly unfixable problems I've had in the past have been due to intermittently grounding ht lead and excessive gap between the coil and the flywheel magnet.

[isha]

Wish I could help but my fallback technological response to my strimmer acting up is to blame my husband for running it badly and this may not assist you.

[765489]

My 20 year old strimmer is fcked aswell. It's like a gear for turning the head is broken, hit the throttle, head not turning. Will be giving it to the local repair man to see if he can fix it for me.

[CelticRambler]

My diagnosis would be that the carb isn't providing enough fuel. I had the same issue with a cheap strimmer and a new carb off Amazon fixed it.

I'd check the high (H) screw and open it out a bit, most would 3/4 to 1 3/4 of a turn out from being gently seated. Although as I'm sure you know its not always that simple and the low (L) screw may also need adjustment.

This machine, this carb, doesn't have a "high" or "low" screw, or at least not of the usual adjustable kind. Well, there is a "low" screw that acts as a backstop for the throttle, but that's not the problem end. In any case, I started it up again this afternoon without any adjustment of anything, other than a squirt of WD40 over the cover of the HT lead/spark plug connector (coz why not ...) ; same story - quite happy to run at low and mid revs for as long as I wanted, but after a token whizz at high revs, it walked off the job.

Until I was ready to walk off the job (having done everything I wanted to do) - then, when I decided to run it at max to use up the last of the fuel in the tank, it ran at max speed without complaint until I'd run out of garden to tidy up! This time, I gave up before it did ...

Will find some part of the neighbourhood to strim in the next few days and see if it's back to normal, and if it is, then maybe I'll re-fit the old carb and see what happens.

[490808]

Picture of carb?

Can't remember whose the regulations are (certainly Califonia's) that prevent new 2 Stroke carburetors having any user adjustment.

If you have two domed heads with indentations of some sort then they could the the H & L Screws only you need a special tool to fit them. I bought I set on Amazon as I had yet another similar problem with my brand new Husqvarna hedge trimmer.

[CelticRambler]

Can't remember whose the regulations are (certainly Califonia's) that prevent new 2 Stroke carburetors having any user adjustment.

If you have two domed heads with indentations of some sort then they could the the H & L Screws only you need a special tool to fit them. I bought I set on Amazon as I had yet another similar problem with my brand new Husqvarna hedge trimmer.

Ahhhh, it'll be that funny black doobery above the fuel intake point, then? (Visible in the third picture on this page [can't directly link the image])

[490808]

Not so sure as there should be two if there is both an H & L screw?

Thats the right side of the carb to be looking as they are normally on the same side as the throttle cable screw which you have mentioned.

[490808]

Check the 5th picture in the Amazon link for some possible jet adjustment points I've not noticed before.

[CelticRambler]

The throttle "backstop" screw is another "pacman" type head, so I'd assume it's the L for this particular carburettor model. I've added that set of tools to my Amazon wishlist, so will play around with the settings in due course. Today's bit of work was a bit tedious but ultimately satisfactory and sets me up for an entirely different project, so I have time to figure things out slowly.

[490808]

nah, there should be a H & L mix screw along with the backstop screw for adjusting the throttle trigger position.

L provides the fuel on idle but the H is the mix adjustment that controls the amount of petrol going into the carb as you open up the throttle.

But that all seems to have changed in some newer carburetors.