Just started to misfire one day

dcstrawn92

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Dec 19, 2014
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Okay here my situation. i was riding my bike one day on a 10 mile journey to my school. I was about 7 of the 10 miles when i thought my bike was starting to run out of gas. I knew i had just put gas in the day before so i was thinking there was a leak that drained the gas out. Checked the gas tank to see that it was still about 3/4 full of fuel. So i limped my bike home so i could see what was the matter. I thought it was a fuel mixture problem. I broke the bike in with a 16:1 oil gas mixture and has since reduced it to a 20:1 I emptied all of the fuel and tank and completely washed it out with water to make sure there were no particles in the tank. I cleaned both of the fuel filters and there were no particles in them. I ended up taking the carborator completely appart to see if anything was clogging the jets and nothing was in there. I adjusted the c-clip just to make sure the right amout of gas was getting into the engine which had no affect on the problem. I looked at the electrical system to see if there was any problem with that. There was little to no spark coming for the spark plug. I replaced the spark plug with an ngk plug and put it to the gap of .025. It started to work okay for about the first mile and then began to misfire again. The next step i took was to replace the CDI box which greatly reduced the misfiring for about ten miles, but then the problem came back up again. There is now no spark created by the spark plug. Im not sure if this could be a problem with the magneto. Could you please help me out.
 
mag is easy to test with a meter - could just be a bad ground

20:1 seems high, so you may be clogging the muffler

also check that engine mounts aren't loose making carb shake too much
 
What setting should the tester be on? And what readings should I get. If 20:1 is too high what should the fuel mixture be? I just tightened up the engine mounts yesterday and the problem is still there.
 
I like 32:1 and the goal is not to make the mounts tight, but to be sure the motor is tight - one should not be able to push or pull the motor sideways while holding the bike frame

set your meter on ohms and look for either 350ohm or 480 ohm (plus or minus about 20%) from the blue wire to a ground bolt at the head - if bad, then test around inside mag cover for a bad ground
 
okay i don't think it was the oil gas mixture just because im not even getting a spark right now. the motor is tight so i don't think that's the problem. for the ohms test it tested inside the parameters but still doesn't create a spark. i replace the spark plug but it still doesn't spark. any other suggestions.
 
may be a bad CDI, but you should look closely at your spark plug cap to see if it is broken inside
 
i tested both of my cdi's and it seems like both of them have gone dead. Is it possible that my original and a replacement went dead after not much use.
 
last month. I had 2 new ones go bad within an hour or so - 3 weeks ago another new one died - this is not common though and I suspect that the new 480ohm mags may be a problem with some of the CDI units - all the ones that went bad were the newer rubber-boot type
 
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