What is normal temperature of air cooled engine?

You can run engine on your parking lot if:
1.there is fan in front of your bike
2.you have infrared thermometer to check head temperature.(no, not your head, cylinder head! )
3.you know normal temperature of running engine (I don't)

I have fan and thermometer but I don't know normal temperature.

A nice large box fan blowing on high speed should be plenty of air to run your bike in the driveway.

No clue on the head temperature, but it's fairly normal for the oil temperature to reach 300F when running an air cooled bike on a hot day.

BTW, running a bike in the driveway sans fan blowing is really bad for the engine. I've bought a couple different bikes over the years where the previous owner left the bike running in the driveway in an attempt to clear carb problems and the pipes turned blue among other things.

And never run your bike during the winter unless you plan to take it out on the road and get the engine/exhaust fully hot long enough to clear out all the condensation that forms when running the bike in cold temperatures.

I have a Honda XR650l which is air cooled, dry sump with the oil in the frame. I have a temp gauge that goes in where the dip stick is up by the head stock so you can see it while riding and monitor accordingly. One thing that has amazed me is how the variation in oil temperature varies very little between a 70 degree day and a 100 degree day doing the same riding. I'm impressed by how efficient air cooling actually is. I can only assume it's because the heat of the engine fins is so high that even 100 degree air temp is significantly lower and still cools the engine. From my experience the engine oil actually gets hottest when riding at high speed with the associated higher rpm for extended periods or when climbing steep hills off road, where you are using quite a bit of power while going fairly slowly. If I see 300 degrees, I slow down, switch it off or head off downhill so it can cool down. It does very quickly, the same if you stop and turn the engine off, I think the frame acts as a big oil cooler. I have not noticed city driving and waiting at stop lights to increase my oil temp much at all.

I don't know how hot engine externals get, never having had a way to measure it, I think head temp is about 500 degrees, exhaust 600. I would still think the oil temperature is probably a better guide in many ways to how hot the internals might be getting.

I use a big box fan if running the bike to sync carbs, check timing etc. that helps cool the header pipes which is where the big heat build up will occur sitting stationary and running at low rpm.

+1 on Nessim's point about not starting your engine without travelling far enough to get it fully warmed, probably 10-15 miles,that's a recipe for problems. I hear a lot of people saying how they drove their vehicle round the block every few weeks while it was basically siting unused, when it comes time to sell it to you. They seem to think that's a good thing, but bearing in mind most of your engine wear occurs on cold startup (80%)and not warming the engine properly will cause condensation to form inside the motor, particularly if you live in an area that has damp air in winter time, proper preparation for long term storage where the vehicle just sits, is a much better option. I think the only benefit from driving the vehicle around regularly would be stopping some of the seals drying out but at the detriment to just about everything else.

There is an old thread or two around here in which OMR posted some comprehensive temps. Try searching for it or pm OMR and ask if he would repost them.