Carbs rebuilt, new plugs ran great for a month, plug that misses was black, checked and it fires great when grounded...rear cylinder
SOURCE: 46 cc Sears/Poulan chainsaw will not start
Four things I can think of:
1) There is a short in your spark plug wire. When you bend it to connect the plug in the machine it allows the exposed cable to contact the engine block. Examine the wire all the way to the coil.
2) Flywheel key is sheared ( you obviously know how to take off the flywheel since you checked the seals).
3) Flywheel air gap is not set correctly. Loosen the coil. Put the cover of a notebook or the cardboard piece of a cigarette pack between the magnetic portion of the flywheel and the coil. Tighten the coil down. This will get you the proper gap.
4) Your cylinder/piston or rings are scrubbed out. Even though it passed a compression test, on rare occasions it will loose compression only when it fires. So do the following:
Remove your exhaust manifold. Look into the cylinder with a flash
light. You are looking for scratches. Anything larger then a light
fingernail is definite proof you need a new cylinder/piston assy.
If it passes that test do the following:
Pour
mixed fuel straight into your cylinder until 1/4 full. Slowly pull your
saw over while looking into the cylinder. If you see bubbles after the
ring/rings go by then you need a new cylinder/piston assy. On rare
occasions if no scratches are present on the cylinder wall or piston,
you may be able to change just the rings.
First if you can get a inline spark tester so you can see if your getting spark with the plug installed.
SOURCE: yamaha fazer is miss firing
I have had the same problem. It is not the spark plugs - although it is always a ggod idea to change them to eliminater them as a potential issue.
The Spark plug holder can be a problem - in my case the wires leading from the ignition lead into the holder - had started to work loose- a common problem apparently. Solved by changing the holders.
SOURCE: 1979 suski 750,bike runs on 2 left side cylinders,
Hi and welcome to FixYa,
With the indulgence of craigjamesbt...
A few additional ideas to consider:
Would appreciate a postback on results/updates on any developments.
Good luck and thank you for using FixYa.
SOURCE: misfire forward cylinder
First you'll need to get a jet kit from West coast star. Then you'll need to jet the carbs to run equally. This may take some trial and error. Another thing that worked on my bike was the upgraded coil kit they sell. It's almost double the voltage of the stock coils and comes with better insulated wires for a more uniform resistance. I haven't had this problem since. It'll make the cylinders fire evenly and save you from those pestiferous fouled plugs. I hope this helps.
SOURCE: Hi I have a 1989 Yamaha Virago the rear cylinder
better look at carb-there r 5 diff jets but its probly the mid range one-be careful here because rong ajust can hurt engine-u hav a clymer manual? library has many books on mc maintenance-sayonara
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