ignition problem on my T140D Special 1979 mod. Spark is weak on the right cylinder and fails to spark from time to time, resulting in loss of power. At idle engine run fine, but there is a 50 degre C difference on the exhaust pipe telling me that the spark is partly missing. Have checked the timing ok. Compression ok. Coils ok measured to equal ohm. Wireing to spark plug ok. Spark plug cap ok. Where to look next? Is it just to get the whole electronic ignition system changed? Please advise!