Stihl chainsaw not starting

[the snooper]

its a little strange you were using it then it wouldn't start again, that's quite a sudden breakdown I would have expected some bad performance or hard starting if the carb parts were deteriorating, with no fuel in the saw you should be able to squirt a little into the carb and get it to fire up, years ago I acquired a stihl with the same problems, turned out that the rings were stuck

 

[rich r]

Yes, I still don't understand why it was fine in the morning (started as normal, ran fine whilst I cut down a couple of dead willow trees and made a pile of logs for the boiler), but it wouldn't start at all in the afternoon. Yet I can't see anything obviously wrong other than it's chucking petrol in and not igniting it. I might measure the compression and see if it seems reasonable.

 

[octo0072000]

try the old fashioned way either a new plug
or warm the old plug up over a gas stove till it's hot and burnt all the old petrol off etc refit the plug as hot as possible see if it starts

 

[rich r]

Got the carb kit today, so after another failed try at starting, I removed the carb again. Changed the diaphragms, gaskets, and needle valve and it's lever. Reassembled the saw, and it started on the first pull of the cord Blew out a bit of smoke on startup (I guess the oil that was left in the crankcase and exhaust muffler), but then idled nicely.

It now bogs down at high rpm - would I be correct in thinking I just need to lean off the H needle screw a little? Probably because the new metering lever is sitting slightly higher than the old one (I checked with a steel rule that it was flush with the body, but I suspect the old one was maybe slightly lower). Or should I take the carb top off again and bend the lever down a little?

I'm at least happy that it now starts and runs, and you guys were spot on that it was a carb issue

 

[shenion]

Depends on how it bogs down. If it starts 4-stroking, it is too rich.

Try adjusting the high speed either way, a little bit at a time. I prefer to keep it a bit rich, just where it sputters a bit unloaded (runs cooler and more oil.)

I have had the same issue with new carb kits. Seems the newer diaphragms are a bit different.

 

[rich r]

The new metering diaphragm is a lot softer and more floppy than the old one, this is true. Whether that's because the old one has hardened with age and exposure to petrol, or because the new one is made of a different type of rubber I don't know.

I'll turn the H screw 1/4 of a turn one way and see what happens, then try it the other way if it makes the problem worse.

 

[Julian_P]

The new metering diaphragm is a lot softer and more floppy than the old one, this is true. Whether that's because the old one has hardened with age and exposure to petrol, or because the new one is made of a different type of rubber I don't know.

.

The old one will have been destroyed most likely by the ethanol in this ****e petrol we get at the pumps nowadays.

The last time I was at a chainsaw place buying some new chain they were recommending this petrol for small engines:

http://www.aspenfuel.co.uk/

Julian

 

[normspanners]

I didnt know that was available on the blurb bit shows a stihl so they must endorse it, how expensive is it?

The old one will have been destroyed most likely by the ethanol in this ****e petrol we get at the pumps nowadays.

quite agree petrol is not designed for carb vehicles nowadays, and diesel isnt designed for diesels !! well not for them to last anyway.

 

[Julian_P]

and diesel isnt designed for diesels !! well not for them to last anyway.

Indeed, the extra refining processes to remove sulphur I believe strip the fuel of its lubricity and I don't think the oil companies add sufficient additives to compensate.

For my old Astra van with 1.7cdti engine I've taken to putting about 1/2 pint of regular engine lube oil into every tankful of Diesel in the hope that it will prolong the life of the high pressure fuel pump.

I'd be careful of doing this with anything modern with the daft particle traps though.

Julian

 

[Keith 66]

i just read this thread with interest as father in law has a stihl saw that refuses to start, he spent hours the other day trying with no joy. sounds like a carby service kit to me!

 

[jordan1]

Is there a spark?, I had a similar problem with a saw, turned out to be the coil.

 

[normspanners]

Is there a spark?, I had a similar problem with a saw, turned out to be the coil.

read the first post!!

 

[rich r]

Um, does the C1Q-S57A carb in the MS180 have L and H mixture screws? They look blanked off.

In which case, I guess I'll have to bend the needle valve lever arm down slightly to make it less rich.

 

[Wendelspanswick]

Are they blanked off or do they have those irritating Pacman screws like the Ryobi stuff?
My father in law has a Ryobi leaf blower and its a PITA to tune, the proper tool is £18 but I managed with a plastic insulating sleeve from a crimp connector jammed over the screw.

 

[rich r]

They're just holes in the carb body, with what looks like an aluminium plug at the bottom, not far from where the channel would be from the metering chamber.

 

[rich r]

OK, so carb off again. There are definitely no H or L screws on this carb. They have brass plugs at the end. I tried bending the needle valve lever down a bit so there's a slight gap between it and the top of the carb, rather than being flush. No real change. I've tried increasing and decreasing the idle speed - still bogs down and stalls at anything much over 3/4 throttle. Choke is definitely going fully open when it should do too. I've made sure the exhaust isn't blocked (no spark arrester mesh on this model anyway), and the air filter isn't clogged (tried it with no filter).

Not sure what to look at next...

 

[Omniata]

The CBE's should have electroning management of the carb so no adjustment to be done

Might be worth pulling the contacts apart and cleaning with contact cleaner then putting back together in case a contacts gotten dirty, there should be two or three behind the flywheel...

 

[rich r]

Are you sure? Carb is a conventional Zama C1Q with fixed jets. No electronics in the saw other than the magneto. But I'm willing to give anything a go.

 

[Omniata]

Apologies confused it with the "M" features of the other saws

Try checking all the contacts though, I've got an MS460W that I added the heated handles too and a better carb, then took the plunge and upgraded from a 52mm to 54mm cylinder...
Doesn't sound much but it went from stock 76cc to 84cc...
Had to upgrade the carb too from a limited one , does race a little but as long as the chainbrake isn't on for more than a minute, or two, it's fine...

After doing the upgrades it was causing me all sorts of grief, turned out to be dirty contacts, lol...

Needless to say now it runs great and cuts really quick!

Edit: get a feeler gauge to check the gap between flywheel rim and coil.
I've got a plate from Stihl that fits between them to set the gap if you need it

 

[the snooper]

on these carbs they have a very fine mesh filter on the fuel inlet and ive seen these block up solid so worth looking at use a magnifying glass to get a good look at it ive even found you a pic of it