The most common thread posted on the old forum was "my bike wont start!"
Maybe this could be stickied so that people can do the simple checks first.
Do not respond to this thread with anything other than facts.
I know this thread is awesome so pm me rather than post here.
Do not post your starting problem here, try the suggestions then make a new thread with as much clear info as possible.
I am not a mechanic but i have some knoweledge of bikes.
This thread is for facts only, anything I have missed please add.
Anyting I have gotten wrong let me know and I will edit it.
The simple stuff.
Its a big red button on the right hand handlebar, make sure its on.
Is your fuel tap off? on? reserve? Try it on reserve if you are low on petrol.
Is the petrol old? if it is drain out the tank and refill with fresh petrol.
Sidestand switch? is your bike in nuetral, if it is in gear it will not start with the side stand down.
FUSES! Check all fuses!
ARE YOUR BATTERY CONNECTIONS TIGHT?
Can you push start it? Put bike in 1st gear with ignition on and run with it(or even better if you get a mate to push you) jump on and release clutch.
Give a little bit of throttle and make sure your on a clear road.
Check all earth connections on frame/engine etc.
If none of the above apply read on.
The basics for an engine to to go are fuel, spark and air.
One is always missing completley, lacking or getting/giving too much.
If you can determine which one is the problem then that makes things easier, if you cant it is a process of illimination.
Is your spark weak?
If your bike is turning over but not starting your spark plugs may be not getting enough power or could be in need of replacement.
Buy a multi metre, they are cheap and will last a lifetime.
Your battery should be putting out about 12.5 volts when the bike is not on.
Charge it for a while and try and start it again if its lower than this.
If your battery keeps dying replace it, if you get the bike running and your battery keeps dying change the regulator rectifier.
Check this golden nuget from eclipze if you think if you think you are having batt/reg rec problems... http://cbr250.com/forum/thread-282.html
To check if you are getting a spark take out a plug attached to the plug cap and touch the metal off the frame.
Hit the starter and check if you can see a blue spark.
WARNING!!! only hold the rubber plug cap and not the metal as you will fry yourself.
If you have the plugs out you may aswell replace them!
If your a cheap ass you may rub them down with sand paper or a wire brush. (or if you know they are relitivley new.)
If your bike is running on less than all four cylinders throw water on the header pipes and see which one doesnt steam off.
If you have replaced the spark plugs and you are still not getting spark replace the HT leads and or plug caps.
If that does not work Check the coils, replace the coils or get a friends coils to test and rule them in or out.
Are you getting fuel?
Is your fuel tap blocked? take off the fuel line from the tank and turn fuel on, if its not dripping out your tap is cloged up.
Are your fuel lines connected properly?
Is your fuel pump working? check with a mulitmeter if its getting power.
Clean your carbs! Clean your carbs! Clean your carbs!
CBRs carbs can get clogged up for many reasons restricting fuel.
Take the carbs apart one by one and use carb cleaner found in any auto shop.
You tube has some good carb cleaning vids.
Check there is no holes or tears in the diaframs (Black rubber nipple things), this can hinder running.
Make sure you clean the jets and put everything back exactly as you found it.
Count the amout of turns in on all idle screws etc.
Inspect the float heights.
Only use petrol resistant silicone to seal back up the carbs, I recomend a product called "indian gasket" go easy with it and its messy!
Thanks to K916 for this "how to clean your carbs write up" http://cbr250.com/forum/thread-231.html
HAVE YOU FLOODED IT?
If you suspect you have flooded your bike, leave it for an hour and try again with no throttle!
If that doesnt work drain the carbs and try again.
If its still not working you may have hydrolocked your pistons, take a plug out and hit the starter for a second.
Put the plug back in and try again.
LASTLY make sure your carbs are on perfectly and tight!
If all that fails burn your bike thats a joke.
Is your air filter durty as hell? change if for a new one.
Make sure your airbox is on perfectly and tight.
MY BIKE DOES NOTHING WHEN I HIT THE STARTER, ZIP, NADDA, NOT A SOUND!
Check battery connections.
Check for corrosion on the starter motor wires/connections.
Check starter button in switch gear for corrosion/connections.
Oh and Info from Studricho,
The main rule to starting a cbr (or any bike for that matter) is don't turn on the ignition until your ready to start the bike.
I've seen so many people turn the ignition on, then fiddle with gloves, then jacket, sit on bike, then forgot to put back pack on, then can't do up helmet with gloves on and then perform a 47 point safety check and decide to hit the starter button with kill switch on for at least 10 attempts.
Battery has dropped in voltage and not enough to crank the engine quick enough, spark plugs fouled and no start.
This is the simple stuff covered.
Hope this helps a few people.