I have a 1986 883 Sportster… the stock ignition system had been replaced with a RevTech electronic ignition with a mechanical advance… over the past week or so the bike would occasionally back-fire slightly when starting… went for a 25 mile ride and took a break… when I tried to start the bike it had a few MAJOR back-fires a few UGLY engine noises and it would not start… I looked at the electronic ignition and found that the mechanical advance unit had broken and tore up the backing plate of the ignition module… replaced both (new Compu-fire ignition) when I set the timing I had the bike on a stand with the rear wheel off the ground and the spark plugs removed so I could turn the engine over by rotating the rear wheel… when I tried to locate the advance timing mark for the front cylinder it was very hard to keep it in the view port, it was difficult to turn the rear wheel then the mark would fly by, again the plug are out… final I would just get the mark into position and blocked the wheel so it would not move… set the timing according to instructions… bike wont start… I have fuel and spark but bike wont start… keep thinking about how difficult it was to keep it on the advance timing mark and if something happened at that major back-fire and how to find out. Your response is appreciated… thanks.

 

ok you have fuel and spark...is the spark good and hot (blue/white) and where is the gas??? in the tank or can you see it squirting into the carb.??...I am thinking that the pet **** may be plugged, and that is why i am asking about the gas....and a weak spark can lead you to other problems....also is there any chance there is water in the tank and you only think you are getting gas when you are really getting water where the fuel should be...

 

Spark looks good... clean plug with correct gap... no problem with the fuel.

 

From your description the ignition timing appears to be where this all began. I would go back and troubleshoot from there.

 

can you move the timing plate while cranking it over??? if you can try and do that and see if you can get the timing close enough to get it to run.....also how close is the new one to where the old one was....what i am wondering is, if the ignition timing is sooo far off that it won't start....

 

Moved the timing plate to a neutral position... more in the middle of the adjustment range... bike started right up... I'll get the timing light later in the week and see how thing go... thanks for the help. I'll make another post after I try to time it with a light.

 

Back on the road again... bike runs as good as ever. I was trying to set the timing to the wrong mark... just following the instruction that came ignition system... on my bike the single dot is the advance mark... used the long clear plastic plug to set the timing with a light... thanks for the help.