No spark after ~2min

Full Tuck /
fowler
Jul 30, 2019 10:29PM

Puch E50

HPI mini rotor ignition

push button kill switch

stock Puch wire block connector for all wiring, non of those clamps

resistor plug boot

history:

first time this happened, it ran over 4 miles an all of a sudden wouldnt do over 25mph (normally hits 45mph)

4 miles has now reduced to about 50 yards and no firing at all

testing (recent):

takes a few pulls to start, kinda weak but fires up

tested with a timing light after it quits -> no spark

stator replaced (new) => no change

swapped in a different cdi box => no change

thoughts:

do HT coils ever go bad?

its not running long enough to get hot.

i havent tried disconnecting the kill switch...i hope thats not it

i cant really check the CDI box(s) with a multimeter... maybe they're both bad

motor was completely rebuilt, im pretending thats not causing any new problems

im not sure i ever checked the spark plug

ok i think i have a pretty good list of things to check, yall are welcome to tell me im an idiot and list off things i forgot

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Re: No spark after ~2min

Don Ohio /
don45640
Jul 30, 2019 11:21PM

Well,you always replace the spark plug first. What about that resistor cap?

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Re: No spark after ~2min

Full Tuck /
fowler
Jul 31, 2019 08:22AM

Guess ill start with new plug, plug boot, plug cable and check for airleaks with carb cleaner if I can get it to idle.

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Re: No spark after ~2min

P D /
pdcomm
Jul 31, 2019 08:55AM

Yes . HT coils do go bad . Not often , but , it does happen .

And , they don't have to be hot when it happens .

You might try removing the resistor from the plug cap and replace it with a piece of solid wire . Your system should be good with only a resistor plug or HT wire , as generally only 5K µ resistance is required .

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Re: No spark after ~2min

Full Tuck /
fowler
Jul 31, 2019 03:39PM

Have new NGK B8HS spark plugs. Was looking at the boot and discovered 2 things, its not a resistor boot and the spark plug cable was kinda loose coming out the the HT coil, I tightened it at least 2 revolutions. So imma gap a new plug and test again... will post results.

Should I also test with a 5K µ resistance boot (I have one)? I know theres been a great debate on moped army over this topic. Some cdis need resistance, people claim HPI doesn't; fiik

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Re: No spark after ~2min

P D /
pdcomm
Jul 31, 2019 08:46PM

You should clip about 3/8" off the end of the HT wire that was in the coil . If it was that loose , I suspect a bit of corrosion there . Also inspect the coil 'screw' that accepts the HT wire for any corrosion .

If the HT wire is resistor type , it should be enough resistance for any system .

But , it shouldn't hurt to try the resistor boot if you usually have good spark .

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