Motoscrubs.com

Hello!

Another request for help. As per my last post, I got my 1968 250 wc running a couple months ago after 20 years of sitting. It ran perfectly for about 10 minutes then started missing badly and stalled. It was not capable of starting but making the odd sputter whilst kicking over.

Plug was wet, so I replaced the starting circuit piston on the VHB30 and cleaned all air ducts very carefully with carb cleaner. This seemed to help a bit. The bike actually started, but was missing badly, sputtering with the odd backfire.

This attempt to start occurred at dusk and my son who was amusing himself watching me, noticed the points were sparking. I don’t know if this is a new condition or not. But for sure these are bright blue sparks at the points when the bike runs. Seems odd to me.

Points and condenser are new from a couple of months. In fact, replacing these is what got the bike running. So these have about 10 minutes of running time on them.

Suspecting a bad condenser (shelf failure of NOS parts?), I removed it and tested it. It measured in at about 0,23 uF. I am guessing this means the condenser is fine and I should look elsewhere…

Thinking back to my epic and ill-fated 10 minute test drive, I recall the bike began misbehaving very suddenly. I am now suspecting the problem is more likely ignition than carburetion related.

Is this sparking at the points indicative of a failing coil? Has anyone experienced this sparking? Any and all suggestions much appreciated…


Thank you!

David

David, what you describe seems like classic condenser failure, both the points arcing and bad or no engine running, I realize you have changed the condenser......but I would try another one again, your ignition coil may well be faulty as well, swap the coil and if possible replace all the ignition system wiring and connectors with new.
Cheers,
George

Thank you George.

The condenser was the first thing I suspected, but the capacitance and ESR values look normal. I have a 400V 0.33 uF capacitor I will try as a test.

All the wiring on the bike is new and working perfectly.

Best,

David

Sometimes all it takes is an installation error that puts the condensor out of circuit. DNAMHIK etc.

Thank you Jordan.

I agree it is easy to mess up the two leads and the plastic washers, but as I mentioned, it ran perfectly for a good 10 minutes.

Recently had some weirdness with my Triumph 500's behavior, replaced the 50-year-old original coils with the most expensive German-made Lucas replicas and the bike's performance improved dramatically.

That's good news.
Where are these German Lucas coils?

Hello!

It turns out it was the condenser after all.

I put a 0.33 uF capacitor in place of the condenser and all the issues vanished. No more sparking at the points.

https://imgur.com/a/8DKN26Y


I wonder where I should buy my next condenser to avoid NOS pitfalls.

https://imgur.com/a/SQDYbZs

Best,

D

Jordan wrote:That's good news.
Where are these German Lucas coils?

'Klempf's British Parts' Coil, Field Gen, E3HM/HB/H. Part No: 200188. $85 each. (12V). Manufacturer, Lucas Electrics

Those who read the old 'Cycle' articles about the evolution of Cook Nielson's 750 Ducati, on which he won Daytona, will recall the difference made by the 'K-mart' coils they picked up for cheap but which threw hellacious sparks that dramatically improved the Duc's performance.

Nick wrote:

Jordan wrote:That's good news.
Where are these German Lucas coils?

'Klempf's British Parts' Coil, Field Gen, E3HM/HB/H. Part No: 200188. $85 each. (12V). Manufacturer, Lucas Electrics

Those who read the old 'Cycle' articles about the evolution of Cook Nielson's 750 Ducati, on which he won Daytona, will recall the difference made by the 'K-mart' coils they picked up for cheap but which threw hellacious sparks that dramatically improved the Duc's performance.

Thanks Nick,
I thought you were talking about ignition coils.

For a time I used one from a 6V VW Beetle on my single.
Just fit under the tank.