No Spark

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mike91
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Joined: Wed Mar 01, 2017 8:39 pm

No Spark

#1 Post by mike91 » Sun Jul 30, 2017 9:33 am

I am rebuilding an 84 350 which is pretty rough and the first thing I have come across is no spark. I found a post on the site which gives some values for testing the stator. Mine checks out between the whites, .6 ohms and the white/green to white/red checks ok, 115 ohms but the values for the other three are different than what I found on here. The brown to red/white gives 4.7 ohms, the green to red/white gives 131 ohms and the green to brown shows 127 ohms.
The bike came with a White Brothers battery eliminator It is being build to be a vintage road racer. Any help would be appreciated. Thanks

silverstrom
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Re: No Spark

#2 Post by silverstrom » Sun Jul 30, 2017 1:33 pm

Typically if there is a failure it will be an open circuit with infinite resistance.

Being an 84 I think you're most likely looking at a stator failure. It is a common problem with 84s.

Remember that you need to test cold. Testing hot will affect your readings. Best to test after the bike has been sitting with the ignition off for hours.

For an 84 you want to see 0.4 ohms +/- 20% for each pair of white leads.

Pick up coil: white/red to white/green = 115 +/- 20%

Source coil: red to brown = 5.3 +/- 20%
Source coil: Brown to green = 225 +/- 20%

Ignition coil Primary: 0.33 +/- 10%
Ignition coil secondary: 3.5 k ohms +/- 20%

Clean all connectors and remove any corrosion.

Don't get too hung up on values. Failures will be very obvious.

MK
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Re: No Spark

#3 Post by MK » Mon Jul 31, 2017 7:25 am

There were three different stators with source coil values between some 130 and 230 ohm.
So your values seem feasible.
The usual damage is that the lower 5 ohm value is infinite (I.e. broken wire)

Possible other causes:
- kill switch cable grounded (black/white ore red/white depending on year)
- wiring (broken cables, loose/corroded connections)
- CDI / rotor / stator combination (there were 3 each, so 9 physically possible combinations, not all running)
- faulty CDI

If I were you, I'd purchase a DC CDI from Zeeltronic or Ignitech. They replace/make obsolete 3 major PITA parts: Stator, CDI, PV controller for the price of slightly more than one of them.
Bye
Martin

mike91
Posts: 12
Joined: Wed Mar 01, 2017 8:39 pm

Re: No Spark

#4 Post by mike91 » Mon Jul 31, 2017 10:42 am

Thanks for the help guys. After poking around some more I think the fault was in the kill switch, I now have spark but it seems like you really have to spin the engine to generate spark. Pulling the top end apart today so we'll see what happens. Thanks again.

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