It might save you money in the long run!
I enjoy DIY projects. Especially when they require power tools. On this occasion, my wife and I were cleaning up the remainder of a tree that we had cut down. We got a friend to help with getting the tree on the ground and cutting up the majority of the tree, but we had a little bit more to do when my chainsaws ran out of gas. I drove to the closest gas station and bought a couple of gallons of gas and came back home and mixed it with oil for the chainsaws. I filled one up and had been cutting for about 5 minutes when it started running poorly and then quit. I grabbed my smaller chainsaw and filled it up and started cutting when the same thing happened. It started to run poorly and then quit. I pulled and pulled on both of then without any luck. I figured if I had a third chainsaw, I could kill it too while I was at it.
What caused my chainsaw to quit?
First, a little background. I knew that both saws were in good condition as I had just repaired both of them in preparation for this tree work. One is an old McCulloch Timber bear and the other is a Stihl MS 170. I had torn the McCulloch down a pretty good way to repair the chain oil pickup tube. When I put it back together, it ran great and the oiler worked too. The Stihl MS 170 was running lean and I had to clean the carburetor. It was running good also when I finished with it. I also knew that the diaphragms in the carburetor were in good condition, flexible and not stretched out or torn.
I figured since both chainsaws stopped soon after filling up with fuel that it was a fuel related problem. I went ahead and checked for spark on both. Both were good on spark. Checking out the fuel system. I put a little gas in the top of the carb and attempted to start the Timberbear. Fired right up and died. Same with the MS 170. Hmmmm, both carbs clogged? I started pulling the Stihl MS 170 carb apart since I had just been into it a couple weeks before and was familiar with how to get it apart quickly.
Chainsaw Carburetor Troubleshooting
Since I had previously confirmed that the carb was not supplying fuel to the engine, I pulled the MS-170 carb off and gave it a quick inspection. I immediately realized what the problem was. The fuel pump diaphragm in the MS 170 carburetor was as stiff as a potato chip and broke like one too. I squirted some carb cleaner through all the passages and they were clear, so I decided the diaphragm was it. It was at least a major contributor if not the entire problem. I pulled the Timberbear carburetor off and disassembled it as well. The diaphragm was not as brittle as the Stihl, but somewhat brittle and stretched. I came to the same conclusion on the Timberbear as well. Both carburetors required new diaphragms.
Effects of Ethanol in Gasoline
I think this example a bit abnormal, although both saws stopped within 5 minutes of filling up with new fuel, it does show how ethanol blended fuel can damage small engine components. I don’t know if I got something other than E10, but whatever was in the fuel caused both saws to stop running. A friend of mine has told me for years to run only ethanol free gasoline in my small engines and outboard. I blew it off saying, I have used blended fuel for years without any problem. I am now a believer when it comes to small engines. Cars are designed for it and newer outboards and small engines, but it is not worth the chance in chainsaws and the like. Ethanol can cause many issues other than what I described.
Chainsaw Carburetor Repair
I ordered a Carburetor rebuild kit for the Stihl MS 170 w/Zama carb, but while writing this blog post, I noticed that complete carburetors for the MS 170 are available for just a few dollars more. Replacing the entire carburetor speeds up the process and does not require removing and installing all those little parts and cleaning the carburetor. Based on my experience with the Stihl MS 170, I would recommend purchasing and replacing the fuel line and filter, oil line and filter, spark plug and air filter. I have had to replace the fuel line on my Stihl MS 170 at least 3 times due the the fuel line getting soft and collapsing. Most likely due to ethanol blended fuel. Here is a good MS-170 Carb and fuel line repair video.
Make sure to verify you are purchasing the correct part before you buy. It appears that more than one model carburetor was used on the MS-170 and Timberbear.
Should I Use Ethanol Free Gasoline
I will only use ethanol free gasoline in my small engines from now on. The minor savings per gallon at the pump is not a savings when I have to make repairs due to ethanol related damage.
There are plenty of good videos on the web to troubleshoot just about any power tool or engine out there. Don’t let a simple equipment failure bust the budget. Many repairs can be done quite easily and economically, so do a little research and give it a try.
If your small engines are running good, use fresh ethanol free fuel to help reduce the type of problems I encountered. Ethanol free is definitely for me!