Remove the resistor from 5K ohm plug caps

[ancientdad]

Since the DOHC450 and 500T use 120° plug caps, finding non-resistor caps to work with the BR8ES resistor plugs is more difficult (and expensive) than other models since NGK stopped selling them in the US. The older resistor caps had a threaded connector for the terminal stud on the plugs and they were easy to convert, but along the way the plug caps were changed to a different design with the connector for the terminal stud on the plug being molded permanently into that end of the cap. As a result, it seemed that we could no longer remove the resistor.

Someone here discovered that the threaded 'spike', where the plug wire connects when we 'screw' the caps onto the coil wires, was indeed removable. I was hesitant at first because it did not seem possible without causing damage, but in fact it can be done. Here are some pictures of how it comes apart and what is inside.

Reach into the end that screws onto the plug wire with a pair of needle nose pliers and tightly grab the threaded 'spike'. Pull hard enough and it will come out of the cap.

The 5K resistor from inside the cap is shown above the sheet metal screw with the two star washers, which provide the friction to hold the parts together in the cap.

This is the view of the inside of the cap with the sheet metal screw and resistor removed. Note the spring inside that keeps pressure on the resistor, holding it against the head of the sheet metal screw.

Not having a larger gauge copper wire on hand, I used a length of copper from a short section of household Romex wire and doubled it over at just slightly longer than the length of the resistor.

Slip the length of copper in place where the resistor was previously, then push the sheet metal screw back in until seated and you're done. Checking the cap's resistance afterward will show 0 ohms.

 

[Banjo1974CB450K7]

Thanks for sharing this with us this is super helpful. I discovered mine was removable by dropping it and noticing all the parts pop out, probably because I also tugged on it a bit too hard installing it.

Did you leave the spring out?

How did you get the length dialed in on the copper wire? Just trial and error and testing it with your meter or did you go a bit long and smoosh it down to make sure it had a good connection?

For me once I put the screw back in it didn't want to stay in. Maybe I just needed to press it back harder but I'm thinking epoxy or something also might help keep it from vibrating apart once it's all together right?

 

[jensen]

If this is not possible, you could also buy a cap without a resistance (0 ohm), for example the NGK LB-F. (90 deg model) The NGK LB05-F or the NGK LB01-F are 5 Kohm, and 1 Kohm) The B fit's the 14 mm spark plugs. The NGK VD-F is the 120 deg model without the resistor. I do understand that altering the cap is a good way to save some money, but if you sell it, or forget it, and use a B8ES (without the R), there is a chance that the the new owner checks the cap, and thinks that there is a resistor in it and might blow up the coil (especially when you using E-ignition).

If you do this, it might be good to label the cap.

I don't know about the US, but here in the Netherlands these caps are available at many online stores, and cost 5 euro or so (the 90 deg model).

Do you run the BR8EIX, the iridium version ? or the BR8ES ? You could also use a B8ES, available everywhere here in the Netherlands, for only 2,69 euro's (https://www.louis.nl/nl/ngk-bougie-...MIi72tkK-XkwMV-JqDBx2GQSW9EAQYAyABEgJmzPD_BwE)

 

[WintrSol]

I found a set of 120 degree 0 Ohm caps for sale in Italy several years ago. They fit better than the 90 degree caps, but are rarely available, and priced that way. Using BR8IX plugs, BTW; won't go back to the non-iridium types.

 

[ancientdad]

Did you leave the spring out?

No, the spring keeps tension on the resistor to ensure connection, so the copper wire used in place of the resistor needs it too.

How did you get the length dialed in on the copper wire?

I used a length of copper from a short section of household Romex wire and doubled it over at just slightly longer than the length of the resistor.

For me once I put the screw back in it didn't want to stay in.

Since you're forcing it out of the cap backwards (against the multi-edged star washer on the screw) when you take them apart, it gouges a little of the plastic away inside the cap. One of mine did that too, so I straightened out the edges of the star washer to make it just slightly larger diameter and put it back in.