first, yes. check the spark.
spark present? move on.
no spark? check wiring. blue and black from motor straight to blue and black on coil. disconnect killswitch completely. check for spark. no spark at this point means measure resistance between blue and black wire from motor. should be in the 350 ohms range. a little more or less is nothing, a major difference (like nothing or a huge resistance) means get a new magneto. if the magnetos fine, its the coil. worth swapping for a new plug before changing the coil, in case.
so...theres spark, but it doesnt run?
disconnect carby from manifold. pour a few cc of fuel down the intake. if everythings good, it should start up, rev up, then die.
this being the case, dismantle clean and reassemble carby.
fresh fuel, no water, raise needle in slide to top, or put eclip in bottom slot, richening the low/mid side of things. stock jet should be slightly too large.... more on this subject later.
if, despite there being a spark, and fuels getting into the engine, it still wont start... remove magneto cover (4 small screws) and check, firstly... that the magnet/ flywheel, has its two round faces horizontal (flats at 12 and 6 oclock). the key (remove the nut and washer to see) should be at approx 1 oclock at TDC, or 7 oclock at BDC. it may have been put in the wrong way around. meaning theres spark but at the wrong time. it wont run
if its ok here, check for oil/residue around the crank seal just under the magnet/flywheel. seal might not even have been installed!
still no luck? start checking the gaskets...the main crankcase gasket, the bottom cylinder gasket, etc.
tighten head bolts.
