Backfire past 3/4 throttle

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Davidsquaredson
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Posts: 225
Joined: Sun Jun 10, 2012 11:41 am
Main scooter: Early Eibar Jet 200
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Hey,
A GP200, 22mm jetex, 125 main, scootrs pipe. Plug chops after a long ride is okay, light tea, could be a bit darker but I did not think alarming. At 3/4 throttle it back fires. Is this electrical? If so why? I can change the CDI and see if that helps, but I'd like to learn what the underlying issue is.

Tx
David
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carpe scooter diem

1974 Rally 200
1965 Li150
1963 TV175
1974 Eibar Jet200
Daggs
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Posts: 776
Joined: Wed Jan 07, 2009 1:23 pm
Location: Addington Kent
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The only time I had a CDi fail. It began with backfiring as the revs went up.
Davidsquaredson
registered user
Posts: 225
Joined: Sun Jun 10, 2012 11:41 am
Main scooter: Early Eibar Jet 200
Contact:

Just as I suspected. Many thanks
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carpe scooter diem

1974 Rally 200
1965 Li150
1963 TV175
1974 Eibar Jet200
Mrnice71
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Posts: 111
Joined: Tue Jul 11, 2017 9:41 pm
Main scooter: Lambretta series 3
Contact:

Light tea plug colour is a bit close to the edge for my liking but the main jet sounds about right if its a standard top end , l like to see more of a milk chocolate colour lol
johnny650
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Posts: 395
Joined: Wed Oct 12, 2016 10:18 pm
Main scooter: lambretta 64 li 150 Special
Contact:

what was the outcome David ? I'm curious .

If it were me and I wanted to try and narrow down whether it was an ignition or fuel related problem I'd probably ride the scoot steady at 3/4 throttle and then apply a little choke and see what happened.
If it was an electrical /ignition issue, the additional fuel shouldn't have any effect on the backfiring but saying that I believe a exhaust manifold/silencer leak can cause backfiring too .
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