Topic: Changing plug cap resistance, how does it affect performance?

[vance]

Bike is a bone stock 1977 CB550.

I decided to install new plug caps because I noticed some arcing from the outside of one of the caps over to the engine. They are the original caps and measure about 10k ohms each. I ordered new OEM Honda caps and when they got here I checked them and they measure 5k ohms. Will it be OK to go ahead and use those or do I need to find 10k caps?

Will the spark or timing be affected be affected by switching to the 5k caps, in what way?

Thanks!

[CycleRanger]

Hondaman explains: http://forums.sohc4.net/index.php?topic=67096.0

[eldar]

The 5K caps are standard. 10k means you should replace them.

[CoachDoc]

Per Hondaman, 10,000 is standard, but the 5000 ohm caps from NGK work fine. Did this on my 550 a while back and it's never run better.

[TwoTired]

The CB550 came stock with 10,000 ohm plug caps.
Changing to 5K ohm will slightly increase the spark current, making the standard hotter range spark plugs wear out a bit sooner (Heat range + EDM), and cause the coils to lose more energy than with 10K caps.
Won't change timing.  In theory, your stock coils will have less than optimal storage at very high RPMs and may misfire (Probably above red line when the plugs, points, and condensers are less than nominal).

If your caps still measure 10K +/- 10%, you could move the rubber bits from your new caps to the old caps, which should solve the spark leakage issues with them, provided they have no cracks.

I don't think most people would observe a noticeable difference between 10K and 5K plug caps.  However, you could keep the new 5K caps and then use R type spark plugs.  (DR7EA).  These plugs have a 5K resistor in them which would add to plug cap resistance, and restore the 10K Honda intended for this ignition system.

If you don't want the old 10K caps, I do, if they are not cracked or corroded.  I'll pay for shipping.  Send me a PM.

Cheers,