MODIFIED ENGINE
Voltage check: For a good battery, the centre "V" LED should light up as soon as the TestMate mini is connected. If the engine has been running immediately prior to this, the voltage may well be a LED or 2 higher.
Cranking: The instant the ignition key is turned (or starter button is pushed) the battery must provide very high current and at the same time remain at a voltage level necessary to get the starter motor running quickly and smoothly. More power is required to start turning a modified engine with increased compression. The stock battery (and starter motor) may not be able to cope with the increased load and could fail sooner than expected. During cranking the voltage will rise slightly after the initial voltage drop until the motor fires. If the voltage does not rise into the green zone the ignition system will provide a weak spark and the engine may struggle to start. If the result is consistently low (red or red / yellow before the engine starts) then it is advisable to fit a battery with a higher CCA rating (e.g. Odyssey / OptiMa or other Extreme types). A more powerful starter motor is the next option.
Charging: With the engine running the charging system should recharge the battery. Expect the voltage to rise slowly towards 14,5V. An even and steady rise is an indication of a good charging system and a strong battery.
NOTES: some power-sport vehicle systems may charge at a slightly higher voltage. This is normal. If a filler cap battery is fitted, check the fluid level regularly. Prevent early failure and extend your battery life by using a charger such as TecMate's OptiMate desulfater-charger or AccuMate range which can desulfate and fully recharge the battery between use.
Notes: Cranking problems: Poor intake / exhaust valve clearance settings or a condition that causes the valve to open less and for a shorter period than required for the engine to run smoothly will also increase compression unexpectedly. Check and adjust valve clearances according to manufacturers' recommendations.