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Post by lcstu on Oct 23, 2021 18:23:55 GMT 1
Hi all, got an RD125 YPVS that tries to start and fires a few times before backfiring and then stops. I have a video but not sure how to attach it.
Carb has been cleaned.
Any ideas please?
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Post by panzermatt on Oct 23, 2021 19:02:30 GMT 1
backfire nearly always electrical. check coil is bolted tight to frame, make sure all connections are kosher. and try the plug.
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Post by jorjasfather on Nov 3, 2021 20:14:27 GMT 1
Hi there have you checked your woodruff key has not snapped
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Post by JonW on Nov 10, 2021 0:23:35 GMT 1
sounds like the timing is way off, something has moved/slipped. As jorjasfather says you should check the woodruff key.
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Post by muttsnuts on Nov 12, 2021 14:03:02 GMT 1
which model, if its a Mk3 then its likely to be the CDI
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Post by museumman on Nov 25, 2021 15:14:58 GMT 1
This woodruff key thing is a bit of a myth, unless you've got a blatant pile of scrap of a bike with a worn crank and flywheel.
A now infamous idiot on the Facebook group equivalent of this forum, has been spreading this to do as a first step of a basic spark test wasting people's time. It's not even mentioned in any workshop book.
The key is just a locator, it's not mechanical. They are pressed into the crank on the YPVS bike so shouldn't fall out either. It also has a little bit of play that disappears once the flywheel tapers are locked up with the nut. Unlike a mechanical key.
I've ridden 6 faulty YPVS bikes just in the last year and 3 engines on the bench. Woodruff keys and tapers all mint. All but one bike was the CDi, now replaced with IgniTechs, that Norbo's shop here, has now ordered in with the correct plugs.
A faulty Cdi on these bikes can still produce a spark and can sometimes rev well enough to make think you can ride up the road, but then fail on the way home.Still running, but with severe power loss. Backfiring is the death.
A couple of years ago guy with a 31K, maybe on this group, put his CDi in the oven and managed to temporary heal it. I copied him and had the same temporary result, enough for me to finish the bike and ride to the petrol station and back. It had then failed when I next came to use it after the summer was over.
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