Spark plug cap

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Spark plug cap

Postby Blurredman » Mon Apr 10, 2017 8:23 am

Hi Guys,

I'm looking to replace my spark plug cap as the one on it now is very worn to the point that engine vibration managed to allow it to come off. This hasn't actually caused me any issue as it continued to run but with the cap just resting on the contact. However it is not ideal.

I use a typical BR7HS spark plug. What is the appropriate Champion or NGK cap for it please?

Many thanks.
1972 MZ ES250/2 - 16,000 miles - The project! :)
1979 Suzuki TS185ER - 9,000 miles - Mud :)
1981 Honda CX500B - 91,000 miles - Long Distance :)
1987 MZ ETZ300 - 38,000 miles - Sun :)
1990 MZ ETZ251 - 49,000 miles - Commute :)

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Re: Spark plug cap

Postby MZCountryRider » Mon Apr 10, 2017 8:31 am

Since you're using a resistor plug, I'd either use a non-resistor cap (no recommendation here) or switch to a B7HS plug and NGK LB05F cap.
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Re: Spark plug cap

Postby Blurredman » Fri May 19, 2017 9:45 am

Thanks MZCountryRider.

I have bought the appropriate cap and it is working nicely and is snug. Thanks!
1972 MZ ES250/2 - 16,000 miles - The project! :)
1979 Suzuki TS185ER - 9,000 miles - Mud :)
1981 Honda CX500B - 91,000 miles - Long Distance :)
1987 MZ ETZ300 - 38,000 miles - Sun :)
1990 MZ ETZ251 - 49,000 miles - Commute :)

ftp://blurredmanswebsite.ddns.net/Vehicle_Documents/MZ_Documents/
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Re: Spark plug cap

Postby Tarwetijger » Tue Apr 24, 2018 4:59 am

Just for future reference, it is quite easy to remove the resistor from the cap. Replace it with a tiny steel or brass rod.

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Re: Spark plug cap

Postby Puffs » Tue Apr 24, 2018 5:16 am

Thanks for the tip!

Does the standard ETZ ignition (battery/breaker/coil) actually benefit from a resistor, either in the cap or in the plug?
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Re: Spark plug cap

Postby Guesi » Wed Apr 25, 2018 12:50 am

The resistor is mostly important for radio interferences, not for the engine.

MZ recommends a non resistor spark plug and a spark plug cap with 1 K-Ohm Resistance.
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Re: Spark plug cap

Postby Blurredman » Wed Apr 25, 2018 2:33 am

Hello,

Tarwetijger, I am well aware of the importance of knowing that a lot of the older caps (not sure about new ones) have removable resistors, as I have had to do this and replace them on my Honda CX500.


I do however for vibration issues recommend the more standard car type cap with only one large nipple instead of the small ribbed shaft that you find a lot on motorbikes. It's not fallen off yet! :lol: :lol:
1972 MZ ES250/2 - 16,000 miles - The project! :)
1979 Suzuki TS185ER - 9,000 miles - Mud :)
1981 Honda CX500B - 91,000 miles - Long Distance :)
1987 MZ ETZ300 - 38,000 miles - Sun :)
1990 MZ ETZ251 - 49,000 miles - Commute :)

ftp://blurredmanswebsite.ddns.net/Vehicle_Documents/MZ_Documents/
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Re: Spark plug cap

Postby Puffs » Wed Apr 25, 2018 3:58 am

Ta for that clear answer Guesi!

Makes sense: the resistor limits the current pulse in the secondary winding of the ignition coil, but the amount of energy in that pulse is quite small anyway, so that it wouldn't do any harm if left unrestricted. I suppose the same applies for more modern ignition systems, like Vape's non-battery based ones, and of course Hall sensor based ones use the original coil.
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Re: Spark plug cap

Postby AlanJ » Sat Apr 28, 2018 4:01 am

Hi M,
That small ribbed shaft I think you will find is the thread for the dolly type nipple which I suspect has been left off as a cost saver by the manufacturers, but to be honest that's just a guess.
Wish you well Alan.
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