Stihl FS200

[pycoed]

Son just brought home a Stihl fs200 strimmer bought as a non runner.

Spark OK

Stripped carb & all looks fine diaphragms intact & look newish, needle valve OK, blew through jets, minimal fuel staining etc.

Tank filter OK, fuel pipes fine, primer bulb good.

End result : will fire & run for a second then stops.

Carb is a Zama CQ with a single adjustment screw which has a left hand thread & a square end, rather than a tapered metering end. This was positioned 5 1/2 turns out from fully in.

Does anyone know the correct setting for this? or does anyone know what the problem is likely to be?

[Gnome]

You could check the spark plug boot for any damage. I had an issue with the boot being in loose contact with the ignition cable. Would work sometimes but the vibrations from the engine would work it loose. It's on the to do list!!!

 

Hope that helps.

[spudulike]

The screw is to adjust the low speed and does so by bypassing the throttle valve - it is a similar carb as fitted on MS181/018/017 chainsaws.

 

You would normally get the machine running and simply adjust this screw until you have an even idle.

 

Your issue is probably the carb, it is probably some crap in it and checking the gauze filter in the pumping section is worth doing, also checking the metering arm height that sits above the diaphragm is also well worth doing - I believe it should be level to the carb body - where the diaphragm sits.

 

If you get the machine running - you will need to define whether it fails to idle at low revs or fails to rev out at the top end - the carb has two sections to meter fuel and this analysis will tell you which area is at fault.

 

It is worth trying another plug - they do play up now and then.

 

Check the fuel lines are OK and that the filter is clean and in place, try running it with the fuel cap loose and see if this helps.

[Ray1]

You mention everything you should be looking at apart from the compression. Had a Fs450 with exactly same issue and the piston was goosed.

[pycoed]

Ta for replies -

1. The plug boot is missing, but there is a ring terminal crimped to the plug lead & held to the plug top with a small nut - looks iffy but seems to work - there IS a spark.

2. Pulled the exhaust which was clear - the exhaust port had a bit of crap but not too bad & the piston looked lovely, with no visible scores at all.

3. I didn't check the metering arm height - I'll pull the carb & dismantle it again to do that. Diaphragms looked fine & carb seemed quite clean inside too, but I didn't use an airline, just looked & blew.

4. My missus has an ultrasonic cleaner which I reckon this carb would fit into - presumably its a complete stripdown then carb body in the US cleaner - what liquid should I use?

6. Assuming wife never finds out about the cleaner - I'll keep you posted.

[spudulike]

Ta for replies -

1. The plug boot is missing, but there is a ring terminal crimped to the plug lead & held to the plug top with a small nut - looks iffy but seems to work - there IS a spark.

2. Pulled the exhaust which was clear - the exhaust port had a bit of crap but not too bad & the piston looked lovely, with no visible scores at all.

3. I didn't check the metering arm height - I'll pull the carb & dismantle it again to do that. Diaphragms looked fine & carb seemed quite clean inside too, but I didn't use an airline, just looked & blew.

4. My missus has an ultrasonic cleaner which I reckon this carb would fit into - presumably its a complete stripdown then carb body in the US cleaner - what liquid should I use?

6. Assuming wife never finds out about the cleaner - I'll keep you posted.

 

I personlly use a water based carb cleaner in my US cleaner but if it is a low powered non heating unit then white spriit will do the job but make sure it doesn't get too hot:blushing:

[pycoed]

Right - feeling like a tit now- I'm back at square 1!

Checked compression - OK at 140 psi after 4 pulls. Pulse hole is clear, pulled all fuel lines & rechecked - all OK.

Stripped carb & gave it an hour in US cleaner with water at 60 deg & detergent. It is now clean with a capital C. All passages & jets are clear.

Reassembled carb after reinspecting pumping & metering diaphragms. Also rechecked metering arm - just level with carb body.

Primed it & exactly the same - it'll fire more often than not, but run only for a second, so I assume it's running only on the excess fuel the primer pulls up?

Although the diaphragms & needle valve look fine to me - even under a magnifying glass, I've sent for a carb kit & I'll fit new needle, gaskets & diaphragms.

Bad week for machinery last week - my diesel mixer (circa 1960 vintage) seized on the second mix of the week too & had to mix tons with a poxy little electric thing.

[mikerecike]

Son just brought home a Stihl fs200 strimmer bought as a non runner.

Spark OK

Stripped carb & all looks fine diaphragms intact & look newish, needle valve OK, blew through jets, minimal fuel staining etc.

Tank filter OK, fuel pipes fine, primer bulb good.

End result : will fire & run for a second then stops.

Carb is a Zama CQ with a single adjustment screw which has a left hand thread & a square end, rather than a tapered metering end. This was positioned 5 1/2 turns out from fully in.

Does anyone know the correct setting for this? or does anyone know what the problem is likely to be?

 

what's your idea of tank filter ok? i've found the slightest bit of resistance when i blow or suck in it directly is a red light - unless you've fitted a brand new one I'd double check

[lakeyboy]

I was lucky enough to pull two of these strimmers in bits out of a skip haha made one good one out of the parts if you need any parts give me a pm ill try and help

 

 

Sent using Arbtalk Mobile App

[pycoed]

Update from earlier posts:

Spoke to son & decided to go for new carb. Whilst waiting for this I compared the spark with an old ( Echo? ) strimmer & the spark was weaker on the Stihl. Dug out my old Danarm with a Kawasaki engine (bought new in 1979 & still works OK) & the Stihl spark was much weaker than that old banger. Hmmm, removed ring terminal & found enough slack in the plug lead to JUST manage to get a proper plug cap fitted. Spark now stronger, carb arrived, fitted & Bingo, starts first pull. Job's a good 'un - well - for son anyway. Me? I'm just perplexed because I STILL can't find anything wrong with the old carb... maybe I'll look for an old FS200 or MS181/018/017 just to see! Many thanks for the info down the line.