I've got a pair of Champion spark plug caps, the box they came in says "spark plug suppressed cover" and has part no. WCX 600. Will these work ok on a bike fitted with a Boyer ignition? And can anyone give a quick tutorial on what a "suppressed cover (cap)" is?
Ignition systems creat a spark that jumps the gap of the spark plug. A spark gap produce radio frequency interferrence (RFI), noise in the frequency spectrum of most radio communications including TV and radio braodcasts. Such RFI makes a car radio noisy and can effect TV viewers close to your path of travel. RFI can be surpressed without greatly effecting the actual spark by placing resistance in series with the high tension wiring of the ignition system. The automobile solution is to use one or more of three choices: resistor plugs that have an internal resistor between the top electrical connection and the spark plug tip, resistive spark plug connectors (commonly called spark plug caps) that have the resistor internal to the cap, or resistive wire which uses a carbon wire that has resistance end to end.
Boyers (except for the digital version) don't like any resistance in the high tension circuit. For that reason don't use any of those three options. Use non-resistor plugs, non-resistor spark plug caps, and hot rod non-resistive wires (Vintage dealers also sell non-resistive molded end cap wires). Since your bike probably doesn't have a radio you should be OK with this approach.
Thanks for the info, all. I guess I'll just keep using the old spark plug caps I have on the bike now. As far as the radio goes, I'll just keep listening to the beautiful music of the 650 Triumph engine!
Bob posted: So which is it then. Should we be using 5k resistance with Boyer or none?
I new this question would come up as soon as I punched the Add Reply button.
In parts of the world you MUST use resistor caps as a part of the safety/annual inspection. This isn't to make your bike any safer or perform better. It keeps your RF from interrfering with other vehicles. You wouldn't want to bother the guy with the new Mercedes with your tick, tick, tick over his radio?...
As a practical matter you do not need to use resistor caps on the original (black box) MKIII Boyer. But you can if you want/or are required to. If the bike doesn't start, or is hard to start, you need, or will soon need, new coils.
Both the Micro-Digital (red box) and Micro-Power (blue box) require that you use 5,000 ohm resistor caps. In this case, the RF interference from your own ignition will cause your bike to miss-behave. It can even prevent the bike from starting in the first place.
Becasue typical resistor spark plug wires are fragile and break easily, Ernie Bransden recommends that you DO NOT use resistor spark plug wires.
You wouldn't want to bother the guy with the new Mercedes with your tick, tick, tick over his radio?
I'll bother him any possible way I can if it helps him realize I'm there and he's required to share the road with two-wheeled vehicles, but strangely that problem seems to be worst with Volvos. I have this theory that the worst possible drivers in the world buy Volvos because they're advertised as being so safe, and therefore not requiring any extraneous driver input (like not running bikes off the road :rolleyes: ) to ensure survival of their occupants.
Sorry for the rant. Back on topic: Another alternative for use with the digital Boyers is resistor spark plugs, but for some reason I don't trust them much more than resistor cable.
"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
Does anyone have a part number for these non-resistor plug wires? After reading this thread, I went out to check my not-so-easy starting T100C and found out that the bike had the resistor type(NGK P/N LB05FP 5K Ohms). I have already gone to the effort of putting in 6 volt coils with my MK III (black box) Boyer, and now I want to go the full route.
My experience....I have a 1968 TR6c with original plug caps (Champion). They have a tendency to pop of the spark plug so I decided to remove the plug caps(NGK)from my 1982 GPZ 750 and replace the Triumph caps. Bad idea...the GPz caps are 5k ohm and I have the Boyer (Black box)ignition. Well everything was fine for the first 50 miles and then the bike began to hesitate then buck. I removed the plugs they were black sooted. Replaced with new plugs got about 30 miles out of those. Then replaced plugs again and made it home with just under 25 miles. I quickly took the NGK plug caps off the Triumph and put an order in for new unsuppressed caps. Mr. W. your correct the spark is suppressed with these caps. Lessons learned from this experience are that the black Boyer does not like suppressed(resistor) caps. See ya in Ohio! Ron
I see the Volvo thing is universal, they do the same in the UK, they wait at a junction, see you coming and pull out just after the point of no return. They have a death wish but its not their death they are wishing for
Not sure of Champion supressor caps but NGK cap at least can be easily converted. Look up inside the cap and you will observe a screwdriver slot across the brass bit that clips to the plug, unscrew that and a spring and a supressor will fall out into your hand. Replace spring and supressor with a square cut piece of silver solder or equivalent and you have "leaky" caps that will burn through the "front end" of a Volvo radio receiver. The potplants who drive such vehicles pay extra for thick glass and other sound insulation so they can listen to Barry Manilow whilst they should be using that sense on the road. I go straight around the glass and get their attention via the radio antenna.
1969 TR6R 7.62 x 51 is not a maths puzzle.
Re: Suppressed Spark Plug Caps#79354 07/05/068:26 am07/05/068:26 am