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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.
<p>hey all my 71 cc scooter starts idles but mont move when i accelarate any ideas what it may be ? if i lift back tyre of the ground it goes when i put it down an accelarate it just revs upbut wont go forward ???</p>
It sounds as if your engine is running as it should. You simply are not getting power through the drive train to the wheel. Is the centrifugal clutch engaging? Is there any kind of locking pin that has sheared? You will probably need to remove shields and follow the drive train to see what is not engaging and what you can do about it.
<p>i dont no if its engaging iam only new to this stuff anything i should lookout for ? if i lift the back tyre up of the ground it spins like mad if i sit it down and accelerate it doesnt move </p>
<p>Thank you for the photos. It appears you have the commonly used drive system, which is a centrifugal clutch on the engine shaft, a sprocket on the drive wheel, and roller chain to connect the two. A centrifugal or speed clutch contains weighted sections held inward toward the shaft by springs. When the speed of the engine reaches a pre-determined threshold, the weights overcome the force of the springs and move outward to a bell-shaped housing that has a small chain sprocket on it. The centrifugal clutch is probably about the only thing that can go wrong. The clutch weights might be stuck with rust or corrosion so they do not engage the bell housing, or the bell housing might have an oily or greasy coating that causes it to slip on the weights, or the weights could be excessively worn and not engaging the bell housing. A new centrifugal clutch is not terribly expensive. Make certain a replacement fits the same shaft size and locks onto the shaft in the same manner as the original, if you decide to replace the clutch, </p>
<p>I put the wrong ratio of oil to gas in my Ryobi backpack blower. I was using it and it started to bog down and then quit altogether. I drained all the gas/oil mixture, added the correct ratio. I've been unable to crank it. Any suggestions?</p>
I had a similar accident with a small garden tiller. I went searching on the Internet. What I found suggested removing the spark plug and putting about a teaspoon of oil into the combustion chamber. Then put a socket wrench with a long bar on the flywheel nut. Turn the engine slowly in one direction only until it is free. Put the spark plug back in, put back any parts you removed, and try starting it. In my case, the engine started and ran fine. I am sure I did not do it any favors and caused some extra wear. We sold the house where we lived at the time and left that tiller with the new homeowner. I cannot say if it is still working, but expect it is.
<p>My son's two stroke 4 wheeler will run fine for a while and when he shuts it off, it won't restart for a while</p>
Here is a link to the problem you describe, but with 4-cycle engines. Still, some things would still be applicable. As it mentions, heat causes things to move. In the case of your 2-cycle engine, a mating surface may be opening and letting in too much air. Check all screws and crankcase bolts for tightness, assuming the gaskets are still good. Is the a good spark you can see when you turn the engine over during the time it will not start? Remove the plug wire and set up a small gap to a grounded wire, maybe with another spark plug. I seem to remember hot start problems can be caused by fuel percolation problems. Is there any reason why the fuel system would have overheated and caused a vapor lock? As the article notes, there could be several different causes. <br><br>http://www.repairfaq.org/samnew/lmfaq/lmedwrwh.htm
<p>Hi, I have a Craftsman 5 HP. Tecumseh engine snow blower. It wouldn't start this year so I cleaned out the carb, changed the fuel, filter and all brand new gas. After priming it the engine starts for a few seconds then dies. I keep pumping the primer as it starts to die and that doesn't do anything to help it keep running. I eventually noticed the muffler was missing a bolt and was not secured and it was damaged pretty good. I'm getting one off Ebay. Would the muffler have anything to do with my issue of getting it to run for more than a few seconds?</p>
Is that a 2-cycle or a 4-cycle engine? If it runs a short time and then dies, that sounds like fuel starvation. You would need to look for anything that could restrict fuel flow or cause the mixture entering the combustion chamber to be too, too lean.
<p>Thank you for responding. It is a 2 cycle. The blower sat for 2 summers and 1 winter without being used. I changed everything from the tank to the carb. I pulled the bowl and cleaned it and the float and needle and sprayed what I could get at without pulling the carb. The carb is probably gummed up. I was trying not to have to pull the carb. I probably need to pull it and clean the whole carb. There's a hole where the bolt that holds the bowl in place that has an opening. Is there a part in there that needs to be cleaned that could be causing this?</p>
<p>I do not work on engines regularly, and do not now own anything with a small engine on it. There was a time when I had to keep a couple of small engines running, </p><p>If the carburetor sat for a couple of years with old fuel in it, chances are real good something is gummed up. Then there is also the total age of the machine to consider. A couple of people here had older machines. Ten years seems to be a tipping point. At that age, gaskets, and possibly also crankshaft seals no longer seal. Air leaks into the crankcase and makes the mixture far too lean for the engine to run. But, those usually do not start and run for a short period. They just do not start, except with starting fluid. Then they stumble and die.</p><p>A lot depends on what type of carburetor your engine has. I know Briggs &amp; Stratton used a pulse carburetor with a diaphragm, but that is usually on 3.5 HP engines and 4-cycle. In time the diaphragm is no longer taut enough to function and needs to be replaced. </p><p>Some carburetors have a float. Those can be come &quot;heavy&quot; by a few grams and they do not shut the gas supply off when they should. But, you see moist gas on the spark plug or running out of the engine and the exhaust smells like fresh gas, if it runs at all.</p><p>I mentioned fuel starvation. That can happen when the vent cap no longer lets air back into the gas tank because the little vent is plugged. But, the engine usually runs for a few minutes before stumbling and dying. You can test the engine by loosening the cap just a bit to see if it no longer stumbles. The air cleaner can be restricted. The fuel filter (if it has one, usually in-line between the tank and the carburetor) could be restricted. It is good maintenance to replace fuel filters periodically, anyway. </p><p>Most small engine carburetors are fairly simple, but there can always be small passageways that are blocked with gums and varnishes from old gasoline. </p><p>And, a main point in this Instructable is that (as above) gaskets are assumed to be tight and sealing, but a mounting screw even one-quarter of a turn loose lets in air that makes the mixture lean. Usually those keep the engine from starting at all, though. </p><p>You could get some carburetor cleaner and spray into the engine. Let it soak. Then blow it out or chase it with starting fluid to clean it out. You will probably need to do this a few times to open up whatever is gummed up. </p><p>As you likely know now, it is a good idea to run the last bit of gasoline out of the machine at the end of the season. I tried to do that with our mower, leaf blower, string trimmer, and garden tiller. When I did that I never had any trouble at the beginning of the next season. (We no longer have any of those machines.)</p><p>If you cannot find the proper gaskets, you can often trace and cut your own from a gasket material you would get at an auto parts store. A mower repair shop can probably get the right gaskets for your if you need some.</p>
<p>I totally thank you for all your help and advice. I found a muffler locally through Craigslist extremely cheap compared to Ebay. I originally changed the fuel, fuel line, filter, spark plug and sprayed carb cleaner where I could and still no results. This time I found more ports and openings that needed cleaning and I double dosed cleaned them. Everything runs great now!! Never again will I leave old gas in there. Thank you again!!</p><p>Rich</p>
<p>Thank you for the good report. I love success stories. It is a bit of a pain to run the engine at the end of the season until the gas is gone, even if you make your best effort to drain all you can from the tank first. It seems so wasteful, but it is worth it. I am glad you got it without too much difficulty. Now, for your sake, I hope you do not have a lot of snow and really do not need to use the blower!</p>
<p>I'm sure i'll regret this but when it ran so good and the satisfaction I felt when it was complete I actually was hoping to get to use it soon. I'm sure after one time i'll be praying for spring.</p>
<p>I am not aware of your location. I spent eight years west of Cleveland, Ohio. We did not get the heavy lake effect snows they got on the east side, but it was still more than enough snow. I was the pastor of a church. The church owned a Gravely 4-cycle tractor with mower and a snow blower attachments. It was parked in a lean-to next to our garage. I did the responsible thing and made certain the engine oil and filter were fresh and the 2 volt battery was charged. I figured I needed to keep the &quot;L&quot;-shaped driveway around our house clear after a storm so I could get to the hospital or someone's house if there were ever an emergency and people wanted the pastor right now. We also had a preschool with a church parking lot that ran between two streets a block apart. The preschool needed to have two wheel tracks across the parking lot cleared so parents could enter from one street, drop or pick up kids, and exit on the other street. After a snow, I was the one on the scene who, by default, made those things happen. I was glad to have such good equipment and did not mind the maintenance work to keep it ready too much. The clearing of the snow, especially ice crystals blowing back into my face did not thrill me. </p>
I'm a yz owner and at the track I've accidentally mixed too much two stroke with petrol and the bike was having problems starting please get back with advice please!
I can only guess. Have you checked the spark plug for oil fouling? The exhaust ports from the cylinder head to the exhaust pipe and muffler could be partially occluded from carbon deposits, depending on how long it ran with too much 2-cycle oil in the fuel mixture.
<p>Also I haven't changed the plug yet. I bought the wrong one. I need to take it back tomorrow and exchange it.</p>
Good day mr. Phil! I have this honda dio 2 stroke 50cc engine, it stocked in a very long time, i would like to restore it, so i cleaned the carburetor change the cdi,ignition coil, sparkplug and statorcoil, i change the oil in the oil tank and a fresh fuel, so it has a fresh fuel,full compression, good spark, and propper lubrication, but it wouldnt start i change the cylinder gasket but it wouldnt start the engine, i am so confused right now what should i do? Thanks!
My engine would no longer start ten years after I bought it. Gaskets between the halves of the crankcase and between the carburetor and the crankcase hardened from age and no longer sealed. When I changed all of the gaskets the engine ran again.
So i must overhaul the engine and replace all the gasket
<p>If the engine is more than ten years old, I would definitely replace all gaskets. I think it is very likely the cure to your problem. All you need for the engine not to start is just a little too much air getting into the crankcase and making the mixture too lean. Gaskets hardened from age make that very possible. I bought some gasket material and made my own gaskets. </p>
Thank you mr. Phil. My engine is running very smooth after i replaced all the gasket. Thank you very much sir and god bless!
<p>I am very happy for you. Thank you for the report. Repair manuals do not mention old gaskets that no longer seal properly. I suppose you are not expected to keep your engine, but to buy a new one.</p>
<p>hi, i have a craftsman leaf blower (358797310) that i just changed the spark arrestor gaskets on. now when i turn it on, it blows blue smoke and has a high pitch noise.</p>
<p>I do not have any experience with what you are asking. Can you adjust the carburetor to reduce or eliminate the blue smoke? Is the high pitch noise mechanical, like a dry bearing, or a whistling, like air rushing through a confined space? </p>
Its a whistling noise. I will go ahead and try to adjust the carburetor for the blue smoke.
<p>Is there any possibility the gasket can be installed upside down? I know that is impossible in many applications, but I have heard of it happening in other applications. A gasket upside down could plug some passageways and open others, which might make a whistling noise. </p>
<p>Hi there. I have a 2 Stroke Tecumseh 3.5 mower. I loaned it to somebody who then put straight gasoline into it with no oil and then called to say its not running properly. I drained it out when I got it back and refuelled with proper mixture. Now when I use full throttle it starts sounding like a Helicopter and starts billowing out white smoke. Any ideas where I might start looking for the problem? I am a newbie when it comes to 2 stroke engines. Many Thanks</p>
I am sorry to hear of your engine problem. I would not lend my things to that friend again, unless the friend offers to pay for any damage to your engine caused by his error.<br><br>4-cycle engines have oil in the crankcase to lubricate moving parts, especially the contact between the piston rings and the cylinder walls. 2-cycle engines get their lubrication from the special oil mixed with the gasoline. When that oil is not present in the fuel in the proper mixture, the danger is that destructive wear will occur in the engine quickly. A compression check would give a strong clue about the extent of damage. Once damage happens, there is no economical way to restore the engine. You could check on the cost of honing the cylinder walls and installing new piston rings, but it may be cheaper to buy a new engine. If you choose to buy a new engine, look into a short block. It is the bulk on the engine and contains all moving parts, but does not include still useful things like the engine head, the ignition parts, and the carburetor. You would need to install those on the short block with new gaskets where parts need to seal. <br><br>One choice you have would be to use the engine as is, but not use wide open speeds at which you get the visible smoke. If there is scoring on the cylinder walls, the looseness it causes with the piston could cause more wear faster than normal. <br><br>You could remove the head for a visual inspection of the cylinder walls, but will need to install a new head gasket and torque the bolts to the proper amount. You or a repair shop may have a fiber optics device that allows you to peek inside through the hole for the spark plug. <br><br>I wish I had better news for you.
<p>8 hp Suzuki outboard motor spits out oil in the cooling water when I first start the motor. Motor runs great and starts easily. Is the oil a sign of problems coming in the future? Could this be a sign of the head bolts becoming loose?</p>
Welcome to Instructsbles. I have no experience with outboard boat motors. I did a little search on the Internet and learned some outboard engines have an oil tank and the oil system can be out of adjustment, but I think that dealt more with combustion and your question deals more with water cooling. It may be someone else will see your question and give you a better answer. There appear to be Internet fora for outboard owners to discuss problems like yours with other owners. <br><br>Instructsbles is a great site for sharing. Often I came to it looking for an answer, but found none. Then I had to develop my own solution I later posted. One such case concerned an electronic flyswatter that did not spark. Posting what I have done also allows me to have a detailed record for the next time I need to do the same thing, but have forgotten a detail or two.
<p>Hi Phil B, <br></p><p>I am a newbie with very little knowledge of 2 <br>stroke engines, just bought a new Hyundai 33 cc 2 stroke multi tool, <br>every thing was fine on all the heads and then it just stopped. Got it <br>going again but if i pull the accelerator trigger there is no power it <br>slows down and stops. This is brand new so the only thing i can think of<br> is the petrol /2 stroke oil mix. on the instructions it says 40:1 for <br>synthetic and 20:1 for mineral. I bought new petrol and new 2 stroke <br>garden oil that is green, its ingredients says mineral so I put it in at<br> 20:1 was i right to do this and is this the problem?</p><p>any help would be great before I contact the shop I bought it in and look like a fool if it is the petrol/2 stroke oil mix</p><p>regards</p><p>John</p>
Have you taken the spark plug out to se if it is reasonably clean or fouled with carbon? Does the crankshaft turn over smoothly? Does the cap on the gasoline tank allow air to get back into the tank so the engine does not get a vapor lock? In some of the comments I linked a diagnostic site for small engines. It is set up like a flow chart. You have to work through it in logical steps until you find the problem. <br><br>One consideration with new equipment is that if you tweak it, you may void your warranty.<br><br>I wish I could be of more help.
Thanks Phil for the answer. <br>I will have a look and see if I can find the link and run through it over the weekend. I have since found out that the 2 stroke oil is in fact synthetic so I have definitely mixed it wrong even though it is not marked on the bottle. I have since drained the tank and added the same amount of petrol again to bring the mix back to where it should be.<br>regards<br><br>John<br><br>
<p>I retrieved the troubleshooting link. </p><p><a href="http://www.smallengineadvisor.com/members/2stroke/main_screen_2S.html">http://www.smallengineadvisor.com/members/2stroke/...</a></p><p>We had a little 2-cycle roto-tiller. I used some old fuel mixed with 2-cycle oil in it, but the fuel should have been discarded. The engine stopped abruptly after running ten minutes or so. It had seized. I checked on-line. I think I put a spoonful of light oil into the spark plug hole. I do remember instructions were to turn the engine slowly with s large wrench, but in one direction only--no back and forth. It loosened and seemed to run fine after I got some fresh fuel properly mixed. I am sure I added some wear to the engine. </p>
The point condenser has not been changed recently. I don't even know if it can be adjusted. its a fairly simple motor. Any other suggestions that would cause a yellow spark? Spark plug wire or anything else?
<p>It has been a long time since I have dealt with points and condensers, but points become pitted after lots of use and need to be replaced. The pitting also causes the engine timing to change. Condensers can become weak. Sometimes they are even shorted from the factory, although that is rare. It is pretty difficult to get a good blue spark unless the points, condenser, and engine timing are good. </p><p>There was also a time when points were in general use, but pointless ignition systems were coming into general use. Some people made devices to eliminate the points and condenser on engines that normally used them. On a fluke, you may be able to find one of those devices. I had a little module like that for a 1970 Lawn Boy 2-cycle push lawnmower. You probably want to find new points and condenser for your Cushman engine. Perhaps Cushman still makes them available. You will need specs. on the proper gap for the points, too. It may be there is no separate timing setting. I do not know. </p>
Thank you. I will check those.
<p>I have a 1984 ezgo golf cart with a 2 stroke engine. It has ran fine for many years. Then one day it just stopped. It has spark, fuel, and turns over, but wont start. It wont even start with starting fluid. </p>
Welcome to Instructables. Does your engine still have sufficient compression? Does it need a new spark plug? An old plug will show spark at atmospheric pressure, but it fails at the pressure of engine compression?
Yes. the compression is 110. The plug is new, but the spark is yellow. I was told it should be blue. Any suggestions?
<p>Yes, you do need a blue spark. Have the points and condenser been changed anytime recently? Can you get new points and condenser for that motor? The engine timing needs to be set correctly, too.</p>
Hi I bought a 99 Polaris trail boss 250 2 stroke it run nice but it leaks gas for the engine block.. And also i can't floor it or it dies right away
It sounds like the float in your carburetor is heavy and needs to be replaced. A heavy float does not stop the flow of gas into the carburetor. It flows out of the engine block and makes the engine run so rough that it stumbles and dies. Even foam plastic floats absorb gasoline and become heavy.
<p>Hi. I purchased a roughhouse 50 scooter for my son couple months ago. The scooter is having some issues. The mechanic is telling me that we used the wrong oil for it. We used 2-cycle oil and he told us we had to use 2 strokes... I thought it was the same thing? Is there a difference?</p>
Two stroke has always meant two cycle in everything I have ever seen. Is there a lot of carbon deposit on the spark plug when you take it out?
<p>It is at the dealership right now so I cannot check...</p>
My 2 stroke 49cc bike will start but will shut off almost instantly. What is wrong?

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