John Rainford

I've been looking for an aftermarket carb to replace my Zama CIQ S119B, but despite a thorough trawl of the internet I could only find one that is in America. There are other models which are in plentiful supply that took exactly the same as the S119B on the outside, such as the S119C, but that's the outside, could the inside have a different make up ? Any ideas? The Stihl part number is exactly the same on both carbs 1139 120 0601.

After stripping down my saw, renewing the crank bearing seals, cleaning the carbon from the head of the piston and top of the cylinder, trying a couple of different spark plugs and fuel filters, I still have a saw that will sometimes start, run erratically for a minute, shoot out huge amounts of white smoke from the exhaust and then stall, so I am back to aquare one. I am thinking that the excessive smoking is a clue to what might be going wrong. I looked for a spark arrestor in the muffler, but it doesn't seem to have one. The muffler is the same as the one on the Stihl ms 181which is one complete unit, with nothing to take apart. So, what causes excessive smoking and rough running before conking out. Has anyone any ideas what I should try next. Maybe a carb clean/kit. Could my piston and cylinder be the culprit, despite cleaning the carbon from the piston top and cylinder top.

The pitting is all over the top of the inside of the cylinder, it's like little pin pricks all over the surface. The cylinder walls look fine, no scratches, no scoring. My new baring seals arrived today so I installed them. I couldn't see anything wrong with the old seals on inspection. However, the old ones slipped off the crankshaft with ease. The new ones were a much tighter fit. I did an experiment to see the difference between the old seals and the new ones. I put the old seal back on the clutch side and gave it a little squeeze. Squeezing it created a gap between the seal and it's seating. This didn't happen with the new seal, so I'm thinking the old seal has worn and no longer provides a tight air tight fit. I had an issue with putting the piston back in the cylinder. It didn't want to go in as easy as it came out. I made sure I had it round the right way, with the ring pins facing the carb. In the end I had to smother the cyllinder with 2 stroke oil and eventually it slipped in to place. I also got stuck trying to get the cylinder back in to the saw, until a little research showed me that it's much easier on this saw if you seat the cylinder base with sealant applied, on to the saw and then take the main part of the cylinder to the base. I was a little concerned that the gasket sealant was open to the elements for half an hour before pressing the cylinder parts together, but i'm hoping it's not going to be an issue. I used a sealant which is high temp, fuel and oil resistant. I did make one error, which was that I managed to snap the corner off one of the cylinder fins at it's base when trying to get it back in place on the saw. Next I have to decide between putting everything back together, checking the carb adjustment and firing her up or spending out on a compression/vaccum test. Any thoughts?

The reason I am stripping the saw down is to find what is causing it to conk out soon after starting, only starts on cold start and engine reved extremely high without me touching the throttle. I didn't attempt to start it again after that. I have to admit that I can't post pictures because I don't have a good enough phone to do this. Since my last posting I have got interested in the workings and problems with stihl chainsaws and am now not sure that I need to purchase a new piston and cylinder. i have learnt that a layer of carbon on the piston head is fairly normal and the pitting on the cylinder head may not be a big issue, although does indicate a possible fuel/air mix problem. I am now thinking that I have an air leak somewhere. I have checked the intake boot and it is fine. I have ordered new crank seals and will be replacing the gasket sealer in the cylinder. I now realise that the saw needs a pressure/vacuume test to see if it is an air leak. I will pull out the fuel line and check that because it's stripped down already. Anywhere else to check before it goes for a vaccume test?

Thanks Wedgebanger

Thanks for all the help. It was all very usefull. This is where I am with my first stripdown and repair. Everything removed down to the piston assembly. Clues as to the problem are as follows. Lots of excessive oil everywhere, especially around the clutch area. The crown of the piston was covered in a layer of carbon deposits which are black and smooth to touch. The top ot the inside of the cylinder was covered in a layer of carbon and is pitted underneath the carbon. One or two vertical scores at the exhaust port side of the piston. Crankshaft bearings look good under close inspection and rotate freely without any noise. Bearing seals look okay, but do have one area on each seal which is marked. I have cleaned the carbon from the piston and cylinder using a degreaser, but the pitting remains. I now need to decide how to proceed with the repair. I have ordered the seals at a cost of £4.50. I can get an aftermarket piston kit for £ 14 or a piston and cylinder kit for £ 25. Hutzl in China do the kit for £ 13 but are currently out of stock. High temp gasket sealer is about £ 6. Do I start with the seals and see if that works now that the carbon has been cleaned from the piston and cylinder, or do I jump in and do all of the above and hope I have sorted the problem. Any advice would be appreciated. Thanks wedgebanger.

Thanks for all the help. It was all very usefull. This is where I am with my first stripdown and repair. Everything removed down to the piston assembly. Clues as to the problem are as follows. Lots of excessive oil everywhere, especially around the clutch area. The crown of the piston was covered in a layer of carbon deposits which are black and smooth to touch. The top ot the inside of the cylinder was covered in a layer of carbon and is pitted underneath the carbon. One or two vertical scores at the exhaust port side of the piston. Crankshaft bearings look good under close inspection and rotate freely without any noise. Bearing seals look okay, but do have one area on each seal which is marked. I have cleaned the carbon from the piston and cylinder using a degreaser, but the pitting remains. I now need to decide how to proceed with the repair. I have ordered the seals at a cost of £4.50. I can get an aftermarket piston kit for £ 14 or a piston and cylinder kit for £ 25. Hutzl in China do the kit for £ 13 but are currently out of stock. High temp gasket sealer is about £ 6. Do I start with the seals and see if that works now that the carbon has been cleaned from the piston and cylinder, or do I jump in and do all of the above and hope I have sorted the problem. Any advice would be appreciated.

Stripping down my saw and have taken off the muffler, air filter and housing, carb, 4 Torx screws which hold the cylinder to the crank case, clutch and worm gear, flywheel and it looks like I need to remove the throttle linkage which appears to be stopping me lift the cylinder away from the crank case. I have watched some videos of other saws where you just pop the linkage from the handle and then pull it out at the end near the cylinder, but this one doesn't come out like that. Does anyone know how to remove it at the throttle trigger end? I tried to take the top of the handle off, but can't see any screws holding it on. Maybe it just pops off, but I dont want to force it.