Weak Spark on a zip, New Stator fitted but no difference.

fands · Derestricted Danger Joined: 20 Jan 2008 Karma :

My boys 2004 50cc Piaggio zip 2T, unmodified failed to start one morning after running the night before.
Went through the ignition circuit, did a spark test with should see the spark jump between 7-10mm, mines was 1mm if I was lucky, so followed on with a tester and measured correctly 100-140 ohms red & whites wired (pick-up) and measured the output of the stator winding (green & white) that should exceed 50v ac (ideally should be 80v) and was only getting 25v ac so the fault diagnosis as per pedpart tutorial was the stator and pick up needed replacing,
https://www.pedparts.co.uk/blog/piaggio-ignition-fault-finding

So purchased a new one, fitted it and it fired instantly and ran for a few mins of a test ride, once back and he attempted to set off out on it for the evening it was back to square one, very week spark and only measuring 25v output !!

Anyone got any ideas as to why, it can't have burnt out a new stator winding in such a small amount of time could it?

Appreciate any help

bradh511 · Scooby Slapper Joined: 01 May 2009 Karma :

have you tested you rectifier ? or coil could be breaking down?
____________________
Theory 11-10-12 lets hope i get mod 1 and 2 done by the 18th of jan 2013 Smile

fands · Derestricted Danger Joined: 20 Jan 2008 Karma :

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

does it electric start ok.....bad earth??
____________________
nuts about bikes

fands · Derestricted Danger Joined: 20 Jan 2008 Karma :

cb1rocket · World Chat Champion Joined: 30 Jan 2010 Karma :

replaced HT lead and plug and plug cap? Its a combine CDI/coil unit, try triggering it manually with a magnet across the pick up.

25v is low, according to the link should be 50v AC as you have posted

There may be a short/broken CDI unit and you may need to swap this
____________________
Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

bradh511 · Scooby Slapper Joined: 01 May 2009 Karma :

Hi if its a combine coil and cdi my old moped was brand new in 16,000 km i whent throught two of these units...
____________________
Theory 11-10-12 lets hope i get mod 1 and 2 done by the 18th of jan 2013 Smile

fands · Derestricted Danger Joined: 20 Jan 2008 Karma :

mospeed · Renault 5 Driver Joined: 26 Dec 2012 Karma :

Hi, its not easy to diagnose faults without being there but from what you have said, and you sound very competent, I would agree that it is a fault between stator and coil.
I would suspect its the plug where the stator wire plugs into the loom. I have had issues with these myself in the past on Piaggio engines.
If you have removed the loom or redirected it , its worth checking that it is not being pinched by the stand. Sounds strange, I know, but I have had this exact problem, which turned out to be the centre stand pinching the cable.
Have you checked the woodruff key to the rotor, as if its worn it may have allowed the rotor to have moved slightly.
If you have no joy. Give Pedparts a call and ask for Andy. They can be very hard to get through to on the phone, but believe me, Andy is the guy you need to be speaking to. If you speak to him, tell him Pete from Mospeed said to call you. He is very helpful.
Keep us posted, and best of luck