See full version: Two-Stroke Engine Has No Spark: Why and How to Fix It
Now, if you replaced the spark plug and the engine still won’t spark or run, you should proceed to check the ignition coil. To do this, you would also need the spark tester. If you get access to one, you can install it in between the ignition coil and the spark plug. Attach one end to the boot of the coil and the other end to the plug. Pull the starter rope or kick it off and see if you get any spark.
If the engine fired for a short while but died almost immediately, it means that the starter fluid went through the carburetor, burned in the cylinder, and stopped when it ran out of fluid. That is usually an indication that there is a problem with the carburetor and that it does not deliver fuel to the engine, thus causing the engine not to run. here
Two-stroke engines are easy to start, so if yours does not spark or start when you kick or pull it a few times, it means that something isn’t right. Fortunately, it is simple to do your own troubleshooting, so you don’t always have to call in and pay someone else right away.
eReplacementParts, meanwhile, recommends looking into the spark plug and says that the easiest way to check it is just to replace it with a new one since spark plugs are cheap. However, there is an alternative, and that is to use a piece of testing equipment called spark tester, which you probably don’t have.
A problem with the carburetor means that it either needs cleaning or it needs to be rebuilt. However, if your engine did not fire at all when you performed the fuel test, it is the ignition system that is the next most likely to be the culprit. here
You can also pull the lead wire out of the spark plug cap and check its end. If the core wire looks burned or is not visible, that could be the problem. Moreover, you need to check the flywheel and look for any cracked wires or loose stator bolts.
Always use a new key. OEM factory, and new. People will post on here that they used an SAE equivalent key and it worked just fine. They got lucky. These are metric keys, if you live in a town like mine, you won't be able to buy one locally, except thru the dealer.
Are you sure it's the correct flywheel? A flywheel with the incorrect taper could be made to fit on, but will not "seat" properly and most of the holding will be being done by the key. A good way to check would be to smear prussian blue on the snout, install the flywheel, then remove. You'll be able to see where it touched, and didn't. If you don't have good contact all the way around, that's a big problem. If you don't have prussian blue, try any kind of dye, grease, just something that will smear and show where contact is occuring.
There's a couple of things to check.
You should always lap the flywheel to the snout, even if it's got a good fit. I use Clover Compound, but any decent automotive store will be able to sell you valve grinding paste. Put a smear on the snout, set the flywheel on without a key, and rock. Turn it 30 degrees, and rock some more. Do this for 10-15 minutes. Add more paste occasionally. Be sure to clean all the paste off of everything before final assembly.
For transfer ports . 0.00008 to 0.00010 sec-cm 2 /cm 3 here
Where D is throttle bore, in millimeters
Only a decade past, East Germany's MZ was considered to be the repository of really advanced research in high-speed two-stroke engine design, and one Walter Kaaden could be said to have the best grasp of the intricacies of scavenging systems of anyone working in the field. Today, no discussion of two-stroke engine scavenging is possible without concentrating almost exclusively on development in Japan. Japanese engineers did not invent the two-stroke engine, nor have they employed any system of scavenging ports that has not seen earlier service elsewhere. But they have done an enormous amount of basic research directed at quantifying what previously has been known only in terms of generalities; they have established very firm design criteria for the management of factors that once were decided almost purely through cut-and-try experimentation. Of course, none of this would be of more than incidental interest but for the fact that some of the Japanese firms have abandoned their once-absolute policy of secrecy and are sharing what they have learned with the rest of the world. Yamaha, particularly, has made a vast contribution to the overall state of the art by publishing fairly specific criteria for the port timings and areas required for engines of any given cylinder volume and operating speed. Like many others, I knew that port timing and area were interrelated factors, but the job of obtaining and sorting through data on a wide range of engines to establish a pattern, and then experimentally verifying conclusions was too time-consuming and expensive to even contemplate, as an individual. Yamaha has done that work for us, and published enough information on the subject to complete at least my understanding (a detailed discussion is presented elsewhere in this book as a chapter, headed, Port Timing ). From a number of SAE papers from Japan - as well as examples from Germany and the United States -and my own experience, I have also accumulated much incidental information related to the shapes, number and disposition of ports. These factors profoundly influence scavenging flow, which influences horsepower very greatly, and we will for the moment concentrate on them alone. [links]
Crankshaft main bearings seldom are troublesome, except in engines that have been in storage for a long time and have had corrosion at work in these bearings -or unless the bearings have been mishandled. Bearing steels are very tough, but you definitely can pound small pits in the races by injudicious use of a hammer, and pits also can be formed by rusting. Bearings damaged in either fashion should be replaced, as the pits will soon spread and become minor trenches, as a result of an activity called Brinelling , which actually is a form of work-hardening. The bearing's rollers and races have casehardened surfaces, but the metal under this thin case is relatively soft, and it is compressed and released (at any given point) as the bearing turns under a load. If the load is high enough, or the bearing in service long enough, the repeated compressions will literally fatigue the metal, and tiny particles of the surface will start flaking away - which becomes visible as the tracking seen in the races of a worn-out bearing. Any bearing will start flaking at some point in its life; bearings with races damages by rust, etc. will begin such flaking almost immediately. Incidentally, in very highly loaded bearings the flaking may be started by the sharp edges around any interruption in the bearing's surface, if the rollers pass over those edges. Oiling slots in the rod's big-end are prone to develop this kind of failure, and the same sort of flaking is sometimes observed around the oil feed holes in the crankpins of engines equipped with direct-injection oiling systems, like the Suzuki s and Kawasaki s. Remove the sharp edges, and you remove the problem - if any. There is sufficient margin of strength in stock production engines so that the problem does not occur; you may find it in the course of reaching for crank speeds substantially above the stock specification.
Given the disadvantages of the fiberglass-packed muffler, better designs are needed and already are beginning to appear. Yamaha, for example, have quite an effective muffler for their expansion chamber-equipped motocross motorcycles. This one consists of a perforated tube passing through a canister, with the center of the tube plugged to force the exhaust pulses out through the perforations in the first half of the tubes and, into the canister, where they escape back through the holes in the tube's second half and then off into the atmosphere. Passage through the holes, which have diameters of about 5mm, breaks up the pulse, and it is further attenuated by expansion inside the canister. My only concern here is that Yamaha's new muffler may over-restrict the expansion chamber outlet, but given that company's thorough approach to engineering and testing, that seems a remote possibility. However -and this is not my concern, but the AMA's -I doubt that Yamaha's muffled motocrosser is really quiet enough to meet the AMA's 92 dbA limit. Perhaps so; perhaps not. In any case, the expansion chamber is here to stay, and so is the movement to restrict noise. The problems of effective muffling will be solved, and I think my inside-stinger may help with the solution. here
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