When you say gentle warm up do you mean ride off from cold using low revs until engine warms up and no hard acceleration/driving before then?
I have sometimes let bike warm up in driveway with partial choke to keep it ticking over but found that plugs tend to foul up when I do that and bike spits and farts when I drive off. So I would appreciate your suggestions.
Tom,
My rule of thumb is to warm up the bike until the valve covers are "warm" to the touch. That is usually 3-5 minutes depending on air temp and how cold the engine was at start. I use the enricher to start the bike, and then the throttle friction screw to hold the rpms around 1200 or so with the enricher pushed back in. You just do not want to "goose" the throttle or put any load on the engine until it is warm. Then ride off gentle for a few miles until the valve covers are "hot". Should be good to go at that point. Much as you can do, anyway.
TQ