Vespa 50 (V5A) with awful misfire when hot
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'79 ET3
Joined: 13 Apr 2016
Posts: 45
Location: Köln, Germany
Sat Jul 18, 2020 5:09 am quote
My girlfriend's Vespa 50 has a really bad misfire when the engine gets a little on the hot side, for example, after riding at a decent for pace for a good 20 minutes or so. The misfire will then appear out of nowhere and continue to do so every few seconds, making it very difficult to ride. The misfire quite often causes a bit of a backfire through the exhaust, leading me to think that it is an electrical problem.

The ignition coil looked pretty rusted up and the HT cables were knackered, so I replaced these items, along with a brand new plug and cap. It now has a good strong spark and I thought I had solved it, but unfortunately, it still misfires

I now need to diagnose the problem properly. Any ideas what could cause this and where I should starting looking?
bodgemaster
1963 GL, 1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 5333
Location: So Cal
Sat Jul 18, 2020 5:33 am quote
Timing
Hooked
79p200e 66smallstate 85pk50xl 84p125ets 63GL150
Joined: 24 Nov 2016
Posts: 168
Location: Flatness, Tx
Sat Jul 18, 2020 2:12 pm quote
Possibly bad condenser. I had a similar issue. Mis-fire after warming up. New condenser and clean/re-gap the points then set the timing and all was solved.
Hope this helps.
Member
'79 ET3
Joined: 13 Apr 2016
Posts: 45
Location: Köln, Germany
Mon Jul 20, 2020 1:23 am quote
Thanks for the suggestions. I'll get the flywheel off and see what condition everything is in.
Addicted
Old douglas ..smallie with polini 115..super with nasco 177
Joined: 07 Nov 2013
Posts: 606
Location: New Zealand
Mon Jul 20, 2020 4:51 pm quote
smacks of....
needing a New condensor
Member
'79 ET3
Joined: 13 Apr 2016
Posts: 45
Location: Köln, Germany
Thu Jul 23, 2020 11:54 pm quote
Ordered a new condenser off eBay and went to fit it yesterday, only to notice that the flywheel doesn't have the threaded inner for the flywheel puller (plus it's too small). Must be a different flywheel for the non-CDI ignition Vespas. Looks like it should have a circlip in the groove too, but it is missing, so that when I remove the bolt, the flywheel stays in place.

Back to eBay for a circlip!
Member
'79 ET3
Joined: 13 Apr 2016
Posts: 45
Location: Köln, Germany
Mon Jul 27, 2020 11:07 pm quote
Removed the flywheel to pop in the new condenser and noticed this fabric material coming away from the top coil. Is this just a braiding that this applied to the start of the winding (i.e. nothing to worry about?)

Aside setting points gap and lubricating the felt pad, is there anything else that needs to be done behind here?

Thanks

IMG_20200727_193811.jpg

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