SK50M not running, occasional spark

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hessam
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SK50M not running, occasional spark

Post by hessam » Tue Nov 28, 2017 12:46 am

Hi everyone, I'm new here.

So the story is I bought my first scooter, a 1997 SK50M, not running. It had been sitting for at least 2 years. I got it home, drained the fuel tank, cleaned the carb, hooked it up to a car battery and tried to get it going. It would almost start, smoke would come out the exhaust but it wouldn't fire and run. Kind of like almost firing, as if out of fuel. The plug would come out wet. I tired this again for a couple of days, then the next day it randomly started right up first try and ran like a clock. No problems at all. I was very happy.

I actually left it idling for an hour and it started right up again as if it never quit.

Then, it wouldn't start a day later. Tested for spark, and it would maybe spark one time and then not again. It has a very weak and very intermittent spark. When I let go of the start button and then try testing for spark again a few minutes later, it would maybe spark a very small amount for a fraction of a second and then stop sparking.

I have unplugged and cleaned all the electrical connectors with contact cleaner. I have the Honda service manual but since I don't own a multimeter (and I don't know how to use it, but an electronics tech friend of mine does, might ask him to take a look but I wanted to see if someone had some good advice here first)

I cut back a bit of the ignition coil lead in case it was corroded. Tried a new spark plug too.

Unsure what else to try.

Thanks
Hessam

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Re: SK50M not running, occasional spark

Post by tiny » Thu Nov 30, 2017 7:23 pm

your generator/stator might not be charging the battery. if you have a voltmeter get her started again and check if its charging the battery. Should read 13V at idle and over 14+ when applying throttle.
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hessam
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Re: SK50M not running, occasional spark

Post by hessam » Mon Dec 04, 2017 5:44 am

Thanks for that. I will check that when I have a multimeter. I also discovered that when I removed the starter relay, used a jumper wire to bridge two of the four terminals so that the starter continuously runs, I have spark. However once I install the spark plug I cannot get the engine to start. It almost does, and smoke starts coming out the exhaust, then when I fit the starter relay back in that's when I lose spark again. The spark seems to only work when the jumper wire is on the starter relay plug, as if the problem lies in the starter switch. But if this was the case why does the engine still crank using the starter switch? Thanks, Hessam

hessam
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Re: SK50M not running, occasional spark

Post by hessam » Mon Dec 04, 2017 9:09 pm

Ok. I have a strong spark when kickstarting, but not when electric starting. However I cannot get the engine to fire! I have spark and fuel, and plenty of air.

Thanks
Hessam

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Re: SK50M not running, occasional spark

Post by Dan Durston » Wed Dec 06, 2017 1:35 pm

Some possibilities are:
- Air/fuel mix ratio is off (e.g. plugged carb jet)
- Exhaust is plugged (sometimes happens on old 2-strokes)
- Compression is no good (easy to do a compression test if you have the right tools)
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hessam
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Re: SK50M not running, occasional spark

Post by hessam » Thu Dec 07, 2017 4:46 am

It does sound like low compression. I will do a test. Thank you

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Re: SK50M not running, occasional spark

Post by hessam » Thu Dec 07, 2017 8:06 pm

Compression test: 140psi. Manual says spec is 142. I think the problem is electrical. Perhaps the spark is not strong enough under compression and blows out. Maybe the stator is faulty and or the cdi or coil. Time to get the multimeter out and start testing.

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