mysterious cut out?

irishpowerjunkie

irishpowerjunkie

Member
I finally got a 2 stroke kit for commuting second hand, had few issues sorted out, but now I think that something electrical is gone, could just be plug I dont know. was riding along running fine for about 8 miles then going up slight hill, ot severe, made it up yesterday, the bike starts to gradually over 100 metres slow way down and cut out, seemed to have a weak spark when checked rolling, may still be on original plug, any help appreciated.
 
NGK-B6HS seems to be the best and most common replacement plug. Have you run it thru a water puddle?
 
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Weak spark is usually caused by a faulty plug boot or wire, if you haven't already replaced the plug wire I'd start there. A good quality auto type 7mm wire core wire works great, the wire may have glue around it at the cdi but it does screw out. At the cdi there is a sheet metal type screw that screws into the wire. A good plug is the NGK b6hs.
 
I only got bike 2 days ago so nothing replaced as yet on engine, broke throttle grip but put on motorbike one from spares bin at home. I might try new plug first as when got it had great blue spark, may have gotten cdi wet, dont know was stored outside as I use it to go to college and back 33 mile round trip everyday.
 
As suggested go ahead and change plug, boot and wire. If no better pull the front left side cover and check for moisture. As a matter of fact -pull that cover first.
 
will try that too thanks. just a question, could I use a bit of jumper cable as a plug lead as have cap but no lead I can use on another repair/resto project.
 
I'll second the irridium plug, It'll be the most reliable plug and it does give off a stronger spark due to less internal resistance. Don't expect a huge power gain, but enjoy a nice smooth running engine with a very trouble free spark.

As for your cutting out problem I saw where you said you left the bike parked outside which could cause moisture to build up inside the magneto compartment, and the magneto does not like water, not even condensation or moisture. The best thing to do here is to remove that cover and seal the opening that the wires come out with rtv. There is a chance the magneto got damaged if it was run and there was water in there so be prepared to buy a new one and replace it, but make sure that cover is sealed really well especially if it has to be stored outside.

The rest of the advice I see in this post is good as well since these things have a weak link at the stock spark plug boot and a better wire and boot is good preventive maintenance. Just very important to not let that magneto get wet as they tend to burn up rather easily when water does find it's way in there.
 
Instead of ignition I'm thinking this sounds more like a fuel starvation issue.
Cuts out at or near WOT? Could be a partially plugged petcock or in-tank screen.

Remove the fuel line from the carburetor, open the petcock and check the flow from the tank. If it runs a steady stream you're probably good. If it drips or barley runs you've found the problem.

That said I concur that getting rid of that plastic spark plug boot is the best thing you can do for yourself and your bike's engine. They are notorious for causing lots of problems. They're junk. Replace it with a good automotive quality boot and a plug with the top cap installed.
Let us know what you find or if you need more help.

Tom
 
had same thing yesterday - saw no fuel in fuel line - jiggled lever on petcock a while & saw fuel - got home and found the small filter in the tank had decomposed and clogged the petcock - cleaned all & OK now
 
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