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Do i need non-resistor plug caps or resistor?

Discussion in 'The Garage' started by njcafe84, Aug 5, 2012.

  1. njcafe84

    njcafe84 XS400 Addict

    My bike is a 78 400e with contact points

    I'm ordering the ignition coils and the 7mm wires from mikesxs and I'm not sure what caps I need.

    Do I order the resistor or non-resistor type?

  2. vectra

    vectra XS400 Addict

    i got the resistor type as i did like you are doing with coils , caps , wires and i got plugs to match what i was getting.

    not had any problem with them so far
  3. bcware

    bcware Well-read Top Contributor

    I am using new NGK resistor caps (5k ohms). I have a '78 2e with points. They appear to be working great!

    I run a bp7es plug.
  4. njcafe84

    njcafe84 XS400 Addict

    I ordered the non-resistor type. Will the bike run with these?
  5. xschris

    xschris XS400 Guru Top Contributor

    Put a set of ngk bpr7EIX plugs in and will be fine:thumbsup:
  6. jaeg

    jaeg XS400 Member

    Hey xschris! I’m a bit confused on plugs right now and was reading this thread as part of my research. I bought some BPR7ES thinking they were BP7ES and have been running them. I still was having some issues and in further digging I also found my caps are resisting 10k-12k ohm. So in an effort to correct everything I ordered some 5k ohm resistor caps and actually a pack of BPR7EIX…

    Now this is where I get confused. I’m not certain if what you’re saying here means using BPR7EIX with a 5k ohm resist cap is going to work. Or, do I need to find 0 ohm resistor caps to work with a resistor plug?

    Your depth of knowledge is greatly appreciated! Thanks in advance!
  7. xschris

    xschris XS400 Guru Top Contributor

    If the plug has the "R" in it the plug is already a resistor plug. You would then need to have a non-resistor cap.
  8. jaeg

    jaeg XS400 Member

    Okay. That’s what I thought after some further reading and I’m glad you’ve confirmed.

    What happens then with what I did? I have the BPR7ES with some 10k ohm caps. I’m wondering if that’s playing part in what my experiences have been lately.
  9. xschris

    xschris XS400 Guru Top Contributor

    Could be. 5k ohms is what most people say is a good number to shoot for.
  10. jaeg

    jaeg XS400 Member

    My question is more - if I have resistors in the plugs and the caps, what does that end up causing? Any idea?
  11. xschris

    xschris XS400 Guru Top Contributor

    Too much resistance.
  12. jaeg

    jaeg XS400 Member

    Yeah. I know that much at least lol

    I assume it means less spark. I’ve been able to ride for a short while but after the engine is hot things go sideways quick. So I’m wondering if spark resistance is even something I need to worry about at that point.

    I’m going to go back to Yamaha spec as best as possible but I’m looking to understand the situation I’ve put myself in to make more informed decisions for the future.
  13. xschris

    xschris XS400 Guru Top Contributor

    That sounds like a lean condition / carb issues.
  14. jaeg

    jaeg XS400 Member

    To follow up on my comment, I found this:

    A wire with high resistance can be in the 5000 ohms per foot range for especially high-output ignition systems, whereas a low resistance performance wire could easily get double digit ohms per foot. Lower resistance means more of the ignition coils energy is going towards bridging the gap or the spark plug. That hotter spark can create a more even burn of the fuel/air mixture in the cylinder, and thus, more power output from the engine.

    This is essentially what I was expecting and would make sense. Considering I have a resistor plug and 10k+ wires, I’m hopeful by going back to non-resistor plug and 5k wires that I’ll have a better experience overall.

    I also agree on the lean comment and will continue working with the carbs.
    xschris likes this.
  15. jaeg

    jaeg XS400 Member

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