All my bikes are 1986 or earlier. All Hondas right now. Scooters, MC's, dirt and trials.
I'm wondering what others think as to whether using spark plugs with resistors and/or suppressor-type spark plug caps (boots) is necessary or even desirable with these older
machines.
My understing is the suppressor system was designed to reduce electrical interference with the car's radio. What purpose, then, does it serve for an older motorcycle with no radio?
In the UK where Nortons and Triumphs are common most users seem to prefer using the NGK #8381 (#LZFH) resistor-less spark plug boots... at least from what I've read.
My 1979 Honda CM-185 Twinstar is specced for a C7HS (resistorless) plug with a (5000 ohm) suppressor boot.
Is there any reason I cannot use a resistor-less boot for an even stronger spark?
Using suppressor spark plugs and caps
Started by
scooterspal
, May 30 2012 05:52 AM
2 replies to this topic
Posted 12 June 2012 - 07:50 AM
I've been doing some more testing of the ignition system on my 1979 Honda CM185T Twinstar.
The right side spark plug exhibits a slightly flaky carbon appearance after a short road test. This is not seen on the left side. Both cylinders (uses the wasted spark system) are fed from a common, dual output 6v coil via a points-type ignition.
Using a modified spark gap tester (made by OEM... any auto store has them) I tested each side. The spark gap for the left was around .09" but only .03" for the right. The spark plug gap called for is .024" so it is clear the one for the right is barely reaching the gap and probably misses more than it fires at the higher speeds.
The result seemingly being the flaky carbon plug.
Rather than go with a new OEM Honda coil for $110, I've ordered one of those generic 6v. dual output coils made for the older Harley's. They claim a 10% higher voltage over standard.
Cost me around $40 with the shipping.
The right side spark plug exhibits a slightly flaky carbon appearance after a short road test. This is not seen on the left side. Both cylinders (uses the wasted spark system) are fed from a common, dual output 6v coil via a points-type ignition.
Using a modified spark gap tester (made by OEM... any auto store has them) I tested each side. The spark gap for the left was around .09" but only .03" for the right. The spark plug gap called for is .024" so it is clear the one for the right is barely reaching the gap and probably misses more than it fires at the higher speeds.
The result seemingly being the flaky carbon plug.
Rather than go with a new OEM Honda coil for $110, I've ordered one of those generic 6v. dual output coils made for the older Harley's. They claim a 10% higher voltage over standard.
Cost me around $40 with the shipping.
Edited by scooterspal, 12 June 2012 - 08:02 AM.
Posted 26 June 2012 - 12:45 AM
The resistors were added to the spark plug caps to reduce interference with radio frequencies. Some resistance is required in the high tension lead to reduce wear on the spark plug, 5K in the cap and a resistor plug leaves you with a fairly weak spark (especially in a 6V system!). I always run a resistorless plug on 6V systems. As a young guy I found out via my smokey 1980 XR80 that the resistorless plugs do survive longer and have a little more pep in an oil burner. Also, in my own stuff I use ND U22FS in place of the C7HSA (NGK = No Good Kind).
I do wish that Honda would spec coils that allow replacement of the plug wire. I have a basket of coils in my shop that are garbage due to bad high tension wires. Tec builds coils for other manufacturers with replaceable coils, why not Honda?
I do wish that Honda would spec coils that allow replacement of the plug wire. I have a basket of coils in my shop that are garbage due to bad high tension wires. Tec builds coils for other manufacturers with replaceable coils, why not Honda?
Edited by theraymondguy, 26 June 2012 - 12:46 AM.
