Mark IV Ohms

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andrew
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Mark IV Ohms

Post by andrew »

Checked out both a new and old MK4 coil today and was surprised to see the HT to ground ohms read at around 1.25K each (with stop wire readings at 0.6K ohms).

The other (Villiers, MK1 etc) coils I have checked over the years read 3.5K-5K on the HT, so wondering if 1.25K is normal for a MK4?

I recall seeing a forum thread on 'normal' reading ranges for all the various coils but can't find it on the search, could anyone point me to that topic?

Only reference I could find for Mk4 ohms is on the following thread which seems to indicate a reading on the HT to ground in a similar range as mine http://www.saving-old-seagulls.co.uk/ph ... +iv#p49508

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Andrew
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Charles uk
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Re: Mark IV Ohms

Post by Charles uk »

The name explains the problem Andrew, CDI, capacitor discharge ignition.

Both of these cdi ignitions have electronics inside that replace the points & tell the capacitor when to let the spark happen with a built in advance function.
It serves no useful purpose measuring the resistance of the capacitor to ground as it tells you nothing about the primary, feeder or secondary coils.

The only way to test a Wipac CDI is to fit and try on a motor.
Make it idiot proof and someone will make a better idiot.
andrew
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Re: Mark IV Ohms

Post by andrew »

Thanks for clearing that up Charles.

Had to replace the HT lead on the older coil, after carefully cutting the plastic coating away just where the lead joins it was easy to unscrew the lead out and screw a new one in. Not sure how well it will work hence the new coil as a backup plan.

Will give the old and new coils a try and see how they do. I understand the mk3 and mk4 ignitions are quite reliable still, with few failures (other than me accidentally cutting most of the HT lead off), is that correct?
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Charles uk
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Re: Mark IV Ohms

Post by Charles uk »

Renewing the HT lead (4mm copper core) is only possible on the MK3 white CDI.

Both of them have auto advance, rev. dependant, give a real nice spark & easy starting, they don't cough & splutter, & if they get a minor ailment they're DEAD!
Make it idiot proof and someone will make a better idiot.
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