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Yamaha Timberwolf 2WD 97 YFB250 Electric Start

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aussietimberwolf
50cc nipper


Joined: 14 Oct 2008
Posts: 5

PostPosted: Tue Aug 25, 2020 1:43 pm Post subject: Yamaha Timberwolf 2WD 97 YFB250 Electric Start Reply with quote Back to top

Hi all,

I am a little stumped with diagnosing this problem. Its been years since I had a chance to tackle this.

I have an electric start problem with my Yamaha Timberwolf 2WD 97 YFB250(K). Its not Recoil/pull cord start related.
Fuel and air are all ok.
If I use the recoil/pull start it will start up first pull, no problems and also runs great. Starts with 1st position choke setting.
When I use the electric start (ignition on, run switch on, and press the start button), it will crank over nice and fast (even used a car battery for testing) but will not always start. Sometimes however, it does start. Once it does start it runs great.
So far, I installed a brand new battery 14AH, a new coil, a new Carby, cleaned and bench tested the start relay and the smaller aux relay, cleaned all the connections. I also adjusted the inlet/exhaust valves. Also a new air filter and new Petcock and fuel filter. Ohms tested the Stator windings OK.
Have not tested the CDI or Regulator units.

So, has anyone else had this type of problem and if so what was the cause and fix?
is there a test procedure for the CDI and Rectifier? (Battery is charging OK)

Thanks.
 
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mech
50cc nipper


Joined: 17 Dec 2020
Posts: 1
Location: New Zealand

PostPosted: Thu Dec 17, 2020 9:51 am Post subject: Reply with quote Back to top

Hi. I'm new so hope it's not too late to reply...

I'd suspect that you have a bad earth somewhere.

What happens is when you pull start it the cdi earths ok, but when the starter is operating it uses the bad earth which causes the earth not to be an earth, but to look like it has some voltage on it, so the cdi isn't earthed but instead has power at both the in and the out leads... So there is no or a low voltage across the internal electronics. Hope that's understandable.
 
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aussietimberwolf
50cc nipper


Joined: 14 Oct 2008
Posts: 5

PostPosted: Sun Dec 20, 2020 10:38 am Post subject: Reply with quote Back to top

Will check it out, thanks
 
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