my crm250 mk2 when fires from cold will run untill warm then die and will struggle to fire again and still then not run .... any ideas please ?

Sounds like carburation mixture, but, initially, put a new BR8ES plug in.
With the old plug removed, and the ignition turned of, and petrol OFF, engage 1st gear, and push the bike along for 20yds or so, this, will vent the crankcase.
Other culprits will be, poor compression, duff electrics= coils or stator, carb settings, blocked exhaust, dirty filter, in short, your bike probably requires a full service to give reliable running.
Mike

cheers mike have cleaned up and reset a few things but will now try your ideas too, many thanks.

cleaned the carb out but to be honest was clean any way, think its time to hand it over to sum1 who knows what they are doing... thanks again for the help

wahoo ! all working again , had carb off several times checked electrics fiddled with mixture and tickover, had exhaust off but everything clear and fine .... then took a while to actually start this time but all working again...

maybe had manflu and just didnt wanna play

maybe you just flooded it, if you leave them standing for a week or two they can be a bit hard to start with out flooding them, mine is ,

i think it could be the petrol in the carb gets weak or can weep in to the engine , so make sure you swich the fuel tap off every time you put it away, this helps to keep a vacume on the fuel in the carb and stops the tanks fuel presure pushing down on the carbs fuel bowl, then theres less chance of the carb flooding the engine if it was to leak abit, if the carb did enpty its self over time ( slow weeping through the flote feed port ) with the tap off the bit that would leak would evaporate by the time you come to start the bike up again,

thats why when you come to start it after a week or two , if its been slowly weeping in the engine and you put the choke on it will flood stright away, then you are kickeing and kicking with out joy,

what i do is , choke on if it dose not start in 3 kicks swich the choke off for 2 kick then choke on again, do not use any throttle at all, when it starts up after 30 seconds get it off the choke and keep it on the throttle.

i always swich my fuel tap off now, and it will fire up in about 2 kicks on choke all the time,

Switch the choke off as soon as you can. Say ~10 seconds. Keep the engine running by gently blipping the throttle when it sounds like it's ging to die.

If you leave the choke on for longer you risk flooding. They are sods to start if you flood them.

Thanks for the tips all sounds like roughly what i been doing to get it going but now i understand a bit better ... Many thanks.

[quote="eddie666"]
i always swich my fuel tap off now, and it will fire up in about 2 kicks on choke all the time,[/quote]

Great tip !!!!

Is this something a lot of people do ??? My bike starts second kick everytime when in regular daily use, but leave it a week or so and its kick, kick, kick, kick......Aways starts after 10 - 12 kicks tho. It then smokes like a bonfire for a few minutes, i get some really angry looks from ECO-neighbours :-) A blast down the road and all smoke clears within a minute or so.
Does the excessive start up smoke indicate anything starting to fail ??? It always happens when left standing even if its been trashed within a inch of its life before being turned off previous to help burn off any unused 2 stroke in the pipe.

I do use TTS fully synthetic and did wonder if it was that as some threads indicate that this may not be the best 2 stroke for a Trails bike over say a RGV250.

i think its the fact that the fuel in the carb is a very tiny amount like a egg cup full,

if you were to throw that amount on the ground with in a few mins it would evaporate,
so over a week or two the octaine in the carb must get weaker because there is air ports above the carb bowel so the fumes ( the good burning stuf , octaine ) can avaperate, leving a weak mix of fuel in the bowel, if your carb is not weeping through the flote valve the fuel will get a bit lower in the bowel so when you switch the tap on it will fill it up again with a bit of fresh fuel thats been in a big tank of fuel that will have kept its octaine better because of the volume of the fuel in the tank ( i always fill up my tank up before i put it away ) this will help keep the octaine high and stop your tank from rusting on the in side if its left for long times.

swiching off the fuel tap will help stop any weeping carbs and it helps the tap from sezing , on most four strokes and some old street two strokes the fuel taps have a vacum pipe to make it work, if the engine is not running no fuel will leave the tank,

All great tips this is really helping thanks guys...

Mine also smokes like hell when started from cold but i found if you start it but switch it off after about 10 seconds leave it a couple of minutes ( put ur gear on or summit) then start it again it helps alot.