Danny Boy
With the air temperature fairly high at the moment it won't take long for the hard revving little motor to get itself excited. Do you know that it is running hot (by actual measurement) or do you just feel that it is? For an air cooled twenty year old bike I wouldn't say that mine runs very hot, but if you are used to more modern stuff its cooling system, relatively low oil capacity and lack of oil cooler might seem a bit primitive. If it is running very hot the exhaust down pipes should be an indicator - are they blue/silver or glowing red? If the former I would think your concerns are from the high ambient air temperature (low worries within reason), if the latter it could be a serious timing/fueling problem (big worries pretty soon), if its somewhere in the middle running it rich will help in the short term but it will need sorting to avoid, on going, long term problems. Have you checked the valve clearances?
Probably not much help in exact terms but the CB250RS is a very tolerant little big that will, as I try to prove, put up with a lot of abuse and minimal servicing!
Cheers
Boyd
