Introduction: Curing 2-cycle Engine Problems
Many 2-cycle engines have problems and are sent to the junk yard before their time. Typical problems include hard starting, rough running, a need to adjust the carburetor during use to keep the engine from stalling, a need to rev the engine to keep it from dying, and not starting at all.
I will assume the user knows to replace the spark plug regularly, to use fresh fuel, and to replace or clean the air filter.
With time and normal vibration, the screws that seal the crankcase from air leaks loosen just a little and air gets into the engine through leaks in the crankcase gaskets.
First check the mounting screws for the carburetor and tighten them. Then go to the screws that hold the cylinder head to the crankcase body and those that cover the end where the crankshaft comes out of the engine. See the yellow circles on this photo of a weed whacker engine. If any of these screws loosen as little as a quarter of a turn air begins to leak into the engine and the fuel/air mixture either is not pushed into the engine on the piston's downstroke or it becomes too lean for the engine to run by pulling in extra air during the piston's upstroke.
After about ten years of use, no amount of tightening on these screws will make a dead engine run. Chances are the gaskets have become hardened beyond their ability to seal the engine. Dismantle the engine completely and install new gaskets. You may not be able to buy the proper gaskets, but you can buy a sheet of gasket material. Use the old gaskets or the engine castings as a pattern to cut new gaskets. Your engine will run like new again.
Step 1: Clean the Exhaust Ports, Too.
Remove the muffler. The exhaust ports are under it. In time carbon residue from the burned oil in the fuel mixture begins to close off the exhaust ports. An engine is an air pump. What cannot get out blocks what needs to get in. Move the piston to the downstroke position (most distant position away from the spark plug) and knock off carbon deposits with a screwdriver. Turn the engine over by hand a few times to blow the carbon granules out of the engine.
Once I used our small 2-cycle garden tiller. After ten minutes the engine siezed and stopped. I had mixed 2-cycle oil with the gasoline, but it was old by the time I was using it. I found advice on the Internet that said to let the engine cool. Then use a wrench with a long handle to slowly turn the engine over. Turn in the same direction, not back and forth. That engine still works very well, although I am sure it suffered a little. Lesson learned: always use freshly mixed fuel.
When a gasoline engine of any kind will sit unused for any length of time, drain the fuel from the tank and run the engine until all remaining fuel in the system has been burned through the engine. This prevents gums and varnishes from closing off small openings.
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I recently purchased a 86 Suzuki lt250r 2 stroke atv now when I bought the atv it ran good but you had keep giving it gas so I research it first thing I see is start it warm it up n adjust fuel/air screw to were it idles just right so that's what I did I noticed after I did that it did start to smoke more white smoke out of the exaust also there is oil coming out of exaust but I heard that was normal for a 2 stroke so anyway went to start it one day after riding it 2 days in a row wouldn't start pulled plug it was bad got new plug started right up yesterday went to start it today won't start pulled the plug black oily / maybe burnt gas smells like fuel more than oil on the end of spark plug. Any advice on what could of caused this and white smoke from exausy would be greatly appreciated all I am completely new to 2 strokes my first one.
I am not a small engine mechanic. In this Instructsble I simoly offered some thngs I found that are not always discussed in troubleshooting charts and their cure.
Here is a link to a troubleshooting chart for 2-cycle engines.
It is not always a fast prccess, but explore possible solutions to problem descriptions that most closely describe your symptoms. Be sure you are using new clean fuel properly mixed for your engine.
Hello so my inline trimmer,starts up idles perfect.but when the throttle is pulled it fires an gos even a couple times of pulling the throttle,youll think it's good to go,you go to start using it an then it starts to bogg down I think they call it.
But only sometimes dies mostly when throttle is fully pulled it pulse's at a low idle,let go an it gos back to the regular idle setting....plz plz help
I would not be surprised if you have an air leak in one of the gaskets due to a loose screw. Have you worked through the things in this Instructable?
how to install uncaged needle bearings on 2 stage snow blower crank
i do not inow. Check YouTube for a video on it.
I have a champion generator. The plug is good. It fires fine and runs until it gets hot then bogs down. Any ideas?
Does your carburetor have a float, or is it pulse carburetor using a diaphragm? If it uses a float, the float could have absorbed enough gasoline over the years that it has become hesvy. When the engine warms up the fuel becomes hotter and less buoyant. The float does not shut off the flow of gasoline when it should snd too much enters the engine, causing the engine to stumble. Also check to see if debris is blocking the air flow through the cowling and cooling fins. If these things are not your problem, do an Internet search for hot run problems in a 2-cycle engine.
I have a 2 cycle back pack leaf blower. It starts up ok when the choke is closed and runs half choke, but when I open it up all the way the engine bogs down and shuts off.
The answer to your problem is in the Introduction above. You have an air leak, probably from a poirly seated gasket. Choking the engine reduces the amount of air entering through the carburetor so the mixture is more nearly what it should be due to extra air entering through leaks. Tighten carburetor mounting screws and crankcase screws. Replace gaskets if tightening screws does not solve the problem.