BrianW
Well-Known Member
Rotax Hard Starting.
NGK resistor plug caps are used on many Rotax engines. Model LB05EZ is sold as a 5k ohm ( = 5000 ohms) spark plug resistor cap.
Older plug caps may go high resistance or open circuit. This makes for hard starting, and may overstress the ignition coil etc. A cheap meter with a resistance range can test these caps. A first easy check is the resistance path between the two plug cap clips at either end of an ignition coil. The resistances are additive: two plug caps at 5000 + 5000 ohms plus the coil resistance which is typically 7000 or 8000 ohms - total: 18000 ohms (18 k okm). Faulty values on hand are 40+ megohms (40000000 ohms) and too high to read.
To check the resistor cap on its own, unscrew the cap from the ignition cable. There is a 'wood' screw to capture the wire on the cap.
Resistor plugs are often used with these caps. NGK BR8ES is a 5000 ohm (5k ohm) spark plug often recommended for these engines. These can be checked between tip and central electrode. No failures have been noted.
NGK resistor plug caps are used on many Rotax engines. Model LB05EZ is sold as a 5k ohm ( = 5000 ohms) spark plug resistor cap.
Older plug caps may go high resistance or open circuit. This makes for hard starting, and may overstress the ignition coil etc. A cheap meter with a resistance range can test these caps. A first easy check is the resistance path between the two plug cap clips at either end of an ignition coil. The resistances are additive: two plug caps at 5000 + 5000 ohms plus the coil resistance which is typically 7000 or 8000 ohms - total: 18000 ohms (18 k okm). Faulty values on hand are 40+ megohms (40000000 ohms) and too high to read.
To check the resistor cap on its own, unscrew the cap from the ignition cable. There is a 'wood' screw to capture the wire on the cap.
Resistor plugs are often used with these caps. NGK BR8ES is a 5000 ohm (5k ohm) spark plug often recommended for these engines. These can be checked between tip and central electrode. No failures have been noted.
