Engine quit running

hrichmon@gmail.com

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I was helping my friend install a kit on his bike a while back. It ran good for a short period, and then one day he said it just fizzled out. I took a look at it, and he had rigged it up a little bit. I decided he needed to get rid of his rigged stuff and get new stuff and do it right. so we replaced the spark plug, the CDI and the carburetor. This is becoming an expensive headache. It still will not fire. definitely has compression, and we have triple checked the wires. clipped the connectors and spliced them up. I've done a few of these now, but I'm looking like an idiot. please help
 
Check for spark, make sure fuel is getting to the carb, make sure there aren't any air leaks and I'm sure there are some other steps in trouble shooting these little motors that I can't think of at this time. I'm sure there will be some other members to offer some more suggestions for ya.
 
[email protected] said:
I have never checked for spark before. How exactly do I do that?
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Pull the plug from the head, reconnect the plug wire, hold the plug on top of the cylinder head and either push the bike forward at a good pace, clutch engaged, or suspend the rear wheel and pedal it fast. Look for a spark at the plug electrodes; the little 'L' shaped part on the end of the plug and the center where the 'L' bends over. You should see a blue spark jumping between them with every revolution of the engine.
If no spark, disconnect the kill switch from the ignition circuit and try again. If still no spark and you're using the kit supplied plug, replace it. Check the connections at the CDI and the plug boot. Get back to us with what you find.
Tom
 
I hooked up another brand new spark plug to the CDI but not the engine, and started riding, popped the clutch, held it against the block, and saw no sparks. Disconnected the kill switch, still nothing.

I have replaced the spark plug and CDI

I took the cover off the magneto, and all those wires seem to be connected just fine.

Any new thoughts?
 
the mag could be shot, they are not made that well and there are some rather small wires that can burn out.
 
I took a look at it, and he had rigged it up a little bit. I decided he needed to get rid of his rigged stuff and get new stuff and do it right.

An explanation of the "rigged stuff" might lead to an answer.

Jim
 
Ended up just swapping it with another motor that I had laying around. It runs. However the reason this other one was sitting around is because it runs at 1/2 speed. Anyone ever seen that? it sounds smooth... but just winds up slowly and runs slowly.... and has low power..... installed it on this one... and it's doing the same thing. Now I'm trying to figure out which one will be easier to fix.

the "rigged stuff" on the other was a broken throttle handle being zip tied into place, some new spark plug cap on the CDI... god knows why....

I'm really not diggin the MBs today :-||
 
sounds like a scared cylinder/piston maybe? loss of compression can lead to loss of power. it could be any of a million things. The new cap was prob a good idea, the stock one is horrible, hard plastic. if he didnt install it correctly that could be why. get a new wire+boot from SBP, its like 6 bucks. when you install it make sure the screw goes into the conductor and not the insulation surrounding it

if you think the wire/cap setup you have now works, try testing it for connectivity with a volt meter
 
Replace the "magneto coil" on the motor that stoped running,and on the engine running at half speed,sounds like a loss of compression.
 
Cant say for sure, However the stock spark plug caps from the original coil have been nothing but trouble (for me anyway) and a bad one that isn't connected correctly would definitely keep your plug from sparking. The stock "U" pin in the cap that holds the top of the plug can come loose very easily creating a bad connection. Other than that, If you still get no spark, there is some bad wiring going on. I'm only on my fifth build now, so I too am still learning this stuff.
 
swapped the magneto, and there we go..... ran great.... gave it back to my friend and it ran fine for two days, then did it again.... he changed the spark plug to a good one... fired up... then quite running..... I think I might just quite hanging out with him
 
[email protected] said:
swapped the magneto, and there we go..... ran great.... gave it back to my friend and it ran fine for two days, then did it again.... he changed the spark plug to a good one... fired up... then quite running..... I think I might just quit hanging out with him
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Excellent diagnosis. And that's really funny.
 
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took the coil from the latter and put on the former... it ran... then two days later, dude said it quit again... then he replaced the spark plug... ran for a little while then stopped again..... I’m baffled... hopefully if i turn off my phone for a few days... the problem will just go away hahaha
 
[email protected] said:
took the coil from the latter and put on the former... it ran... then two days later, dude said it quit again... then he replaced the spark plug... ran for a little while then stopped again..... I’m baffled... hopefully if i turn off my phone for a few days... the problem will just go away hahaha
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Maybe the guy should put a little more gas in the tank when he test rides it?
 
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