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Poor Spark and misfiring

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Howard

Poor Spark and misfiring

Have finished complete rebuild of 1973 CB750 K2
Noticed that quality of spark is poor and occasionally it fires on 3, which 3 varies so it would appear electrical.
Have changed coils, condensers and points as part of rebuild.
Have tried coils from a CB250 K4 which I am rebuilding and these produce a good spark.
Any ideas?

cdaiscool

Re: Poor Spark and misfiring

If you swapped out coils and the new coils produce a better spark, then the old coils could very well be suspect.

The new ones you put in, are they new or old? As in, did you buy them used or new?

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TOOLS1

Re: Poor Spark and misfiring

Administrator

In reply to this post by Howard

Sounds like bad plug wires, or caps.
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
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Re-run

Re: Poor Spark and misfiring

Administrator

In reply to this post by Howard

I differ from a lot of people on this topic. I would just replace the coils and wires. Why keep parts that are almost 40 years old? The wires are most assuredly close to wearing out even if coils seldom fail. then you have to drill out the cable and splice a new one in and for what? To use am old coil anyways that doesn't work as well as a new one does.

You can go to partsnmore.com and get new coils like the stock ones, for about 38 each.
That is my fix because I dislike replacing old electrical parts with old electrical parts.

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