Author Topic: Misfire - Old problem remembered !!  (Read 147 times)

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Offline Astute Greaser

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Misfire - Old problem remembered !!
« on: August 02, 2022, 10:14:09 PM »
So just wasted 6 hours of my life and bit of frustration.
I had written a thread about my Voltage Regulator for Bluey my USA RD200C. Thought all sorted and it was. But…………..
I was getting misfire LH side, put down to low battery while sorting VR. Fully charged on Centerstand she revs through the range no probs. Ride the bike underload, misses below 3500 rpm and then fine above.
So swapped known good VR from Goldie my RD200A. No difference. By the way Bluey’s VR works great on Goldie.
So thought what breaks down under load. Sparkplug – Pulled out my new spare, bleeding thing was long reach, where did I get that from  ???. Borrowed Goldie’s. No difference  :(. Tank off and swapped coil with spare, new sparkplug cap and lead. No difference.  :(
Packed up for the night thinking stripping carb in morning. So, I was a fresh. Went to Bluey and thought back to the day when working on cars. Condenser. Got out 48-year-old original and hooray sorted.  :) :) :)
Points and condensers had only done 60 miles. Says Japan on bottom of troublesome LH condenser, from well known supplier who I normally defend on here regularly. However, saying that car ones suffered exactly the same problems. It’s their nature. We always swapped at same times, as plugs every 3,000 miles
Should have thought condenser earlier, just it happened same time as another job. That’s Life  ::)

Offline ajh

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Re: Misfire - Old problem remembered !!
« Reply #1 on: August 03, 2022, 12:42:15 PM »
i had same issue with a new japanese tourmax condensor, changed both points and condensors being careful to fit daichi points but couldnt source Daichi condensors so used tourmax. Did about 20 miles before one side started failing. Put the old condensor back on and all was fine.... Apart from the time spent checking and rechecking the points/timing on that side before realising it was duff!
« Last Edit: August 03, 2022, 12:44:18 PM by ajh »
in Chiswick, West London

77 RD250d(ex), 80 DT175mx, 81 4L0 350LC, 82 GS550Ez, 80 CB750F

Offline martin1957

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Re: Misfire - Old problem remembered !!
« Reply #2 on: August 03, 2022, 02:14:09 PM »
I did see some info on the net once about these components. They are just a paper/plastic film capacitor strip wound into a swiss roll construction. The foils are displaced sideways so one end of the swiss roll is one terminal and the other end the other.

One end is sort of metallised and consolidated and the whole thing dropped into the little can. It presses onto the bottom making the ground contact.

The top has a rubber washer and is rolled over and down, so the rubber pushes the whole thing together.

When the rubber goes hard, the bottom contact breaks down, as the rubber loses its springy compression.

Some older or european ones are made in a different way.

You can fit any 0.2uF paper/mylar capacitor with a voltage rating of say 600V DC and it will work fine.....

I have had success in testing failed ones with a good high impedance DMM to measure open circuit and to also measure capacitance, and do this while they are just too hot to touch. But you really need an HV test as well. Substitution is the best way maybe......


Here we go 

  http://nonlintec.com/sprite/cap_failure/
« Last Edit: August 03, 2022, 02:18:49 PM by martin1957 »
Retired Electronic Test Engineer (Avionics), Age 64, Owned P50, PC50, SS50z, YAS1, YDS7, RD350B till 1978, then in 2009 a  KH400 A4. Have a fully restored YAS1, an AT3, and now two Suzuki T125 Stingers.  One a show winner, one to sell.