81 Darmah Plug Wire Replacement -How?

[900SSDesmo]

I have an 81' Darmah with the Bosch ignition and it appears that the plug wires are trapped/glued in. Does any body have experience changing these - or am I missing something on how you get then out? Talking about the coil end.

Thanks in advance

[MHR1000Mille]

I used a small screw driver the break the seal on mine, the lead itself just unscrews when you replace the lead you can use some silicone or epoxy resin to reseal it.

Cheers Marty

[900SSDesmo]

Thanks Martin!

I owe you a virtual brew for that: you have given me the knowledge to carry on - and I don't have to buy coils.

Appreciatively
Steve

[Ventodue]

Also this from the much-missed John Wilson of Intelligent Ignition Systems (IIS):

" Replacing HT cables on Nippon Denso Coils
(pinky-biege colour, stamped 028700.)

First, carefully remove the epoxy resin around the HT cable entry point on the body of the ND coil. You can do this, for example, by using small side cutters. Take care not to damage the body plastic.

There are two parts to the HT lead:
• the inner HT lead/copper wire with insulation cover
• an outside thin sheath.

Pull hard on the HT lead until it comes out of the coil body tube. This will leave the outer sheath still inside the coil tube. Break this bond by carefully pushing a screw driver down between the sleeve and inner bore of the tube until you feel the remaining epoxy, then continue working around the sleeve until it frees from the bore. There is a standard spike termination at the end of the bore.

Insert a good quality copper core HT lead of 7mm diameter (8mm will not fit) into the bore (tube) until is stops. Then secure the new lead to the ignition coil body using a good quality silicon sealant or epoxy.

Try not to use building grade silicon as it cures by liberation of acetic acid which attacks copper components. Use 738RTV, if you can find it at the local electrical wholesalers; or at least a neutral cure silicon which is becoming more available from hardware stores.

Once done, terminate the HT leads using NGK spark plug covers with 5.0K ohm suppression resistor for clean firing of the spark plugs.

IIS information sheet.
Updated 5th January 2004"

Ciao

Craig

[MitchB]

This is very timely for me, as I'm in the middle of a Ignition System check on my '81 Darmah...
Good info about the NIPPON coils - I too, wondered.

Couple of questions that are related(?):

Do the spark plug covers HAVE to have the 5.0K ohm suppression resistor? Why? I thought resistor plug caps / wires were only to remove static from radios and such...

What is the role of the "ballast" resistors in these Bosch setups?

I just received a set of 5 ohm Dyna coils from BevelHeaven. The Instructions with them say to remove the ballast. Should I?

[900SSDesmo]

Thanks for the detail Ventondue! Most helpful and very much appreciated!

[Ventodue]

Originally Posted by MitchB

What is the role of the "ballast" resistors in these Bosch setups? I just received a set of 5 ohm Dyna coils from BevelHeaven. The Instructions with them say to remove the ballast. Should I?

The ballast resistors are there to permit the ignition coils to operate at less than 12 volts. And why would you want the coils to be able to do this? Because the voltage from the battery often drops below 12 volts when the engine is being cranked over.

However, once the engine is running, the battery voltage recovers back to 12 volts (or more). And that's when the resistors come in. They 'resist' the full voltage of the battery getting to the coils.

Now I think that the original coils were 3 ohm. So if the Dyna coils are 5 ohm, you probably need to ditch the ballast resistors. But don't quote me ...

Originally Posted by MitchB

Do the spark plug covers HAVE to have the 5.0K ohm suppression resistor? Why? I thought resistor plug caps / wires were only to remove static from radios and such...

Resistor caps also have the effect of extending the duration of the spark. However, there's no such thing as a free lunch: the spark tends to be 'weaker' 'cos you lose a bit of energy due to the resistor.

So you can try without using resistor caps. But, as he wrote at the end of his piece, I know John Wilson was always a fan of them.

Ciao

Craig