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'85 Spree Weird "Backfire"

Posted: Tue Apr 06, 2021 7:36 pm
by gothhonda
Hey y'all! Been working on a Spree for the lady out of some parts bikes I had laying around. She's been running pretty well the past few days, a zippy 28mph. It seems to happen randomly, but I'll get some strange throttling when I rev the bike on the stand, almost as if spark is intermittent. A pretty loud bang will come out of the exhaust, then the bike will die.

I've build a few Sprees, and even more scoots, but I haven't ever experienced anything like this before. Is this a timing issue? I was under the impression that these bikes had fixed stator plates- no timing adjustment needed. The exhaust pop sounds like some of my pedal-start mopeds when there's a late spark. Could this possibly be a fuel delivery issue, or an electrical component failing? It's got a fresh plug and coil, and a CDI box that works fine on my other bikes. I have a multimeter, but I'm unsure of the order of operations for testing. Anything helps, thanks!


Julian

Re: '85 Spree Weird "Backfire"

Posted: Tue Apr 06, 2021 8:19 pm
by motormike
Notice any intake or exhaust leaks?

Re: '85 Spree Weird "Backfire"

Posted: Wed Apr 07, 2021 10:47 am
by gothhonda
Not that I’ve noticed! Using the unrestricted pipe, stock carb, stock air box and filter, and fresh gaskets all round.