SOHC.co.uk Forums > CB500/550

CB550 K3 custom project

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thomaspigeon:
@julie thanks!

Out of curiosity, how do you know they have a resistor? The spark plugs were DR7ES so the wrong ones!

I'm wondering if that bike was really running in the past now...

Nurse Julie:

--- Quote from: thomaspigeon on September 06, 2020, 10:14:02 PM ---@julie thanks!

Out of curiosity, how do you know they have a resistor? The spark plugs were DR7ES so the wrong ones!

I'm wondering if that bike was really running in the past now...

--- End quote ---
Those plug caps are standard NGK resisted caps fitted to all Honda CB SOHC/4's. Originally, some models came from the factory with metal, non resisted plug caps so you had to fit resisted spark plugs with that type, or the bike would interfere with all the neighbours TV's. . The metal ones were a pain and a majority were thrown in the bin at PDI and the rubber resisted type were fitted with non resisted plugs.

deltarider:
Hope this pic helps.
How to check plugcaps. Start with checking the resistance in total from one plugcap via the coil to the other plugcap. Realise that new resistor plugcaps are around 5kΩ each. The coils secundary itself is around 14-15kΩ, so with both plugcaps attached, you should read around 24-30kΩ in total. When you read over 30kΩ in total, unscrew both plugcaps to be tested individually. Over time the plugcaps resistance tends to increase. When over 8kΩ, replace. Do not run and resistor caps and resistor plugs. When you have the choice, I'd prefer resistor caps over resistor plugs. Verify plugcaps are firmly connected to the wires. Ofcourse there should be no arcing between plugcaps and/or HT leads and the head. This is best seen in the dark.

Seabeowner:
My CB500 owners manual calls up D-7ES (presume non resistor plug). The metal plug caps had the resistor in them. I have six.

McCabe-Thiele (Ted):
Maybe bikes are different but it's been my experience that most cars I have worked on will start and run on the wrong plug - obviously not very well usually with flat spots or misfires but they do start.

As regards plug caps I have known them prevent running completely when several have failed on a 4 cylinder engine - likewise carbon leads  are IMHO awful give me old fashioned copper wire .

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