Starting point for mixture screws on replacement carb

[John Rainford]

I have a 15 year old Stihl MS 211/C which has been kept going with help from spudulike, peatff and others over the years. I have had a running issue which I think is an issue with the original Zama carb. I have had it in bits and thoroughly cleaned and tried a new carb kit, but that didn't solve the issue. I've checked the fuel line, spark plug, fuel filter, tank vent etc but these all seem fine. Now before anyone starts berating me for buying a cheap chinese carb, I know they are hit and miss and not made to anywhere near the high specs of an oem carb, but i didn't want to pay £ 100 for a zama carb for a saw that is only worth £100 and only used a few times during the winter to cut fire wood. I don't have a mityvac, so can't be absolutely sure it's  a bad carb. have fitted the new £12 carb, but havn't attempted to run the saw yet. Before fitting I checked the position of the mixture screws and the idle screw. The high screw was one and three quarter turns out, the low screw was one and a half turns out. Neither of these were close to the factory spec for the original Zama carb. The idle screw was set at 6 turns out, which seems  odd to me, but I am an enthusiast, not an expert. So my question to the experts is where should I start with the number of turns out for the H, L and Idle screws. Any help would be greatly appreciated.

[Mark Bolam]

I would screw them all in as tight as possible before throwing the saw on a bonfire to guarantee a more satisfactory explosion.

 

Just buy a new saw and enjoy your life!

[spudulike]

I did purchase a spare test carb from China for a 150 and 201 and both were Zama from what I could work out and I have seen enough to know.

 

Anyway, the 201 carb settings...around 1 turn on the L screw and have found they like to be a little on the lean side.

On the H screw 1.5 to 2 turns....1.5 if the exhaust has been opened out.

The H screw usually has some weird limiter that can be drilled and junked or if you wind the adjuster in until the limiter stops you....that is 1.5 turns in.

Next😉

[Mark_Skyland]

Ive seen a few MS211's were the carb was beyond repair, a new OEM carb sorted the problem. They would tick over but not throttle up.

 

I would go with Spuds info but Chinese carbs can cause more hassle than they are worth. I wont entertain trying to tune them in, OK I will for about 30 secs after that its an OEM or back to the owner. 

[John Rainford]

Thanks for the replies spudulike and Mark. I'll give it a go and see what happens. I don't rate my chances of success very high, but you never know.

 

[spudulike]

If you can, stick a couple of pics of the carb up. The one I had, I am pretty sure it was OEM, you may be lucky.

As Mark said, some are shyte...my failures are MS660, MS200 but my BG56 blower was fine. I never found a good MS200 one, utter.....💩

[John Rainford]

Just seen your post from a few days ago spudulike. I have just installed the carb and put fresh fuel in and adjusted the mixture screws to the settings you suggested. I'll have a go at turning it over this afternoon and post what happens. As for the carb I bought for £12 , it's definately not an OEM. The original was a Zama C1Q S119B. This carb has no numbers on it and I can tell that the machining is not as good as an OEM carb. The size of all the external components seems pretty good, but one of the butterflies has different small cut outs than the OEM carb. I did see a few Zama OEM carbs for other saws on e bay, but not for mine.

 

[bmp01]

MS211 carbs, I’ve had some experience with these…..

As you’ve put a carb kit in it and it’s still not playing ball then I’d put money on it being the accelerator pump circuit. It’s well known problem, well documented here and other sites.

Depending how you get on with your replacement carb…. if you want to cover postage costs, send me the original carb I’ll sort it for you. I have one or two MS211 saws to check it on.

 

[spudulike]

OK, for some stupid reason, I thought we were talking about a MS201..DOH, apologies.

The 211, if the symptoms are a completely unstable idle, almost impossible to tune the carb especially at idle, an idle that rises and then completely dies and starting issues....it will be the accelerator pump and would take BMP up in his kind offer as it isn't the easiest if jobs to sort unless you have done a few.

Fixes can be fitting a new pump and O ring which I used to do or some blank off the circuit and richen the mixture which can slow the throttle response but does sort the issue. 

[John Rainford]

Thanks for the replies spudulike and the offer from bmp01to check my original carb to see if it is the accelerator pump. I might well take you up on the offer if my cheap chinese carb doesn't work. I got delayed by the wife falling and smashing her face good and proper. I've been running round various hospitals for the last few days. I just managed to get some time to look at the saw this afternoon. Cheap carb installed and fresh fuel in. I pulled it over a few times in the cold start position and got the tell tale noise that it wanted to start. Moved the switch to the run position, pulled it three times and it started and ran at idle. Let it idle for a couple of minutes and it sounded like it wasn't getting quite enough power to idle comfortably. Turned the L screw out a quarter turn to give it a bit more fuel, but this made no difference. Turned the L screw in a quarter turn, heard the revs creep up and it then idled comfortably. Gave it some throttle a number of times and it reved up well with no bogging. I must admit to being a little surprised, I wasn't expecting  much success with a cheap after market carb. Next job is to start it again tomorrow and try some cutting. I'll post my results.