Air cooled bikes have a fine line with cooling and heating issues. The cylinder fins must remove/radiate heat but must also let the engine warm up from a cold start condition.
Never had a problem with my 1988 KDX 200. Large fins to radiate heat during low speed gruelling trails in the warmest of days. My friend had a 1988 Yamaha DT 200 with liquid cooling. It wouldn't cool at low speeds and would overheat, overflow the coolant recovery system and loose all it's coolant. He bought a small fan for it and I installed it for him. Switch for off and on. Simple and effective. The temp guage would still get into the warm zone but amazingly would cool off to operating temp within a minute of idling at the end of a climb.
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