Minimum temp before running any engine hard should be 200 F, Max temp for an engine should be no more than 280 F but in saying that, don't tune your engine to a specific temp, tune to performance, just stay between them temps. As long as there is a reasonable stream of smoke coming from the exhaust & performance is good then the engine should be fine & if your engine seems to be running well then temps around the 245 F mark you had will be fine as long as there is smoke.
Different brands of engines like to run at different temps, some run a little cooler & some hotter but minimum temp should always be 200+F so the metals in the engine can expand properly causing the fit between parts to be correct & this will also help the engine produce its best power.
Some engines run great at close to 300 F & I have read of a few people running engine at 280+ without problems, although I'm not sure how long the engines last but they have said that is where there engine runs best without problems, other may only be 220 F.
Mine seem to like it a bit warmer, My Alpha .21 RTR engine runs best around 250-260 & my modified GODZILLA .21 Go Engine has been running at slightly lower temps but the weather has been cooler to. The dude who I got my modified engine from runs the same engine with higher compression on 60% nitro in a boat with temps up to 280F & getting speeds of 125+kph.
Keep your engine over 200F & pre-warming it will also help with engine life & will also make it easier to start. Hair dryers are good for pre-warming engines.
To prime your engine, pull the fuel line off the exhaust nipple & blow through it to pressurise the tank & force fuel into the carb, having the carb slightly open will help when doing this. don't suck back through the fuel line or you will get a mouthful.
