Won't start when cold. starts if warm outside, but idle roughens once temp gauge hit second bar. runs roughly after hitting 50 mph

SOURCE: Rectifier Problem

If the battery is charged, its charged..... redpoint5 is right, check the battery when hot... If the battery was not charging i would then look into the charging system, rectifier, etc.... Is it an air cooled engine? Sometimes engines can get a little warped when hot... My grandfather had Corvair vans as taxis that somehow always got overheated, after that they would never start hot. So, he had to leave them running all day.... If your battery is OK you may want to have a look at your starter.... Or, bypass the selenoid with a jumper cable and see if the starter kicks over fine when jumped directly...... That would indicate a bad or worn selenoid.

SOURCE: 2005 CRF450R Hard to start and wont idle

Hi
I would suggest that you have the valve clearances checked.

Also, check that the carb is clean. Pay particular attention to the PILOT JET as this opperates the idle circuit.

Jon

SOURCE: 2002 cbr 954 red light on gauge blinks

sounds like the engine management fault code signal. there is a free download service manual here. with it you should be able to decifer it http://www.carlsalter.com/motorcycle-manuals.asp

SOURCE: 1984 aspencade starts w/choke and revs up, runs smooth. Take off

My 'wing won't run unless it has been warmed up some. I would suggest that you r&r your carbs to make sure the jets in the bottom are working correctly. They tend to get plugged up, especially after sitting & the aluminum flaking off inside... Rick

SOURCE: Runs great when cold, hesitates when hot.

Hi mmagliozzi
I bought a cbr 600 fy new back in 2000. After about 3 years I've always had the same problem in summer when sitting in traffic, ie. anything that put the temperature up to about half way causing the fan to cut in. I thought it was a carb problem. also thought it could be the spark plug caps(coils built in breaking down only when warm).
Anyway, mine had become so bad recently that it had become almost unrideable as it kept cutting out and spluttering, only at tickover and low revs. Anything over 3000rpm it was fine. I thought it might be an electrical problem so put a meter across the battery. It was only showing 11.5v when running at tickover. Rev it up to 2000rpm it was showing about 12.5v. It should at this rpm show more. If you have the same problem you can rule out the alternator by taking the plug of the rectifier/regulator( under the seat cowling, you can access it by removing the seat) and putting the the leads of the meter across the yellow wires. test all 3 wires. ie if you were to number them 1, 2, 3 then test form 1 to 2, 2 to 3 then 1 to 3. You should get somewhere in the region of 20v at tickover and 50v at 5000rpm. If this figure varies by a large amount between each wire ( alternator winding) then the alternator is the likely problem. But i reckon it will be your regulator/rectifier. They are not cheap at £141 from honda. You can get them from ebay but the guy at honda (mechanic)reckons they are inferior and he has had to repair bikes with boiled batteries and burnt wiring looms. This maybe nonsense but I took the safe route. Whatever one you do decide to get(if it is the rectifier/regulator at fault) then make sure it is the cast ally heat sink type not the original one which has the gubbins incased in rubber.I reckon its a design fault with the originals hence the updated replacement which disippates the heat better.
Going back to diagnosing the problem. I found mine by running the bike stationary until the fan cut in, make sure your lights are on then operate the front or rear brake light. by doing this you are loading the electrical curcuit. When I did this my bike cut out straight away or very nearly did so. Yours might not if your battery is very good. If you notice it running worse then I would bet that you have the same problem.
Hope this helps.
Dan