could be improper jetting.
how long have you had the bike? it could be just the bike. when i first got my 450 it took way more throttle to get rolling than any other bike i've ridden but when she's going she's good.

 

has it been re-jeted? u could try turning the fuel screw out or in a bit and see if that helps..

 

Yeah that is what i was thinking as well so I tore the 450s carb apart and went through it and cleaned everything that I could. put it back together and it still would start and idle great and then die... Oh and this is when its not in gear just in N. So I borrowed my buddies 08 450 and took his carb off and put his on mine and it did the same thing I put my carb on his and it ran fine no problems... So now im thinking electrical. It feels like somebody just turned it off. There is no bogging down of sputtering it just stops running. So now im kinda stuck I would really like some help here. I have had it since it was new and the weekend before this porblem came up I was riding it just fine with no problems at all. I cleaned it off and put it in the trailer for the race the next weekend. When I pulled it off the trailer and went to practice this all started. The only difference is that I cleaned the air filter.

 

Yeah that is what i was thinking as well so I tore the 450s carb apart and went through it and cleaned everything that I could. put it back together and it still would start and idle great and then die... Oh and this is when its not in gear just in N. So I borrowed my buddies 08 450 and took his carb off and put his on mine and it did the same thing I put my carb on his and it ran fine no problems... So now im thinking electrical. It feels like somebody just turned it off. There is no bogging down of sputtering it just stops running. So now im kinda stuck I would really like some help here. I have had it since it was new and the weekend before this porblem came up I was riding it just fine with no problems at all. I cleaned it off and put it in the trailer for the race the next weekend. When I pulled it off the trailer and went to practice this all started. The only difference is that I cleaned the air filter.[/b]

anybody know how to check the coil? maybe its not getting enough spark for the extra fuel. maybe change your air filter and use your buddies, maybe you got something on it that is causing this. plug change? im no expert so this is just a few things i would check. could also hook the jumper cables up to a car and leave them on there while its running and see if it does the same thing.

 

check your airways did you leave a rag in the intake when you cleaned your filter? check your connections for your throttle position sensor.

 

are you trying to rev in neutral?! i

 

Yeah im trying to rev it in neutral. I soaked the eng area down with carb cleaner to see if i left a hose off and it didnt change the idle at all so i know i got all the hoses on right. Since this has happened I just took off air filter and lid to see if that was the cause of maybe not getting any air. i have all the plastics off and just the hose from fuel tank to the carb hooked up so that i can see whats going on. I changed the spark plug and the coil. Is there a crank sensor that maybe is not reading right?? Where is the Throttle position sensor. if its in the carb i have changed that and if its under the throttle cover i wouldnt know how to check that. what if the timming is off a little?? but would it idle?? f*&k i have no idea and its driving me crazy. I dont want to take it in they will just charge me and it still wouldnt be fixed and i have to race the 29Th.

 

ive heard of timeing being off a tooth and the bike still running so its possible. i dontk now how to check it though. i would try swaping CDI's with your friend that let you swap carbs. and hopefully someone here can let us know how to check timing

 

sounds like the Throttle Over Ride System to me. when i hooked mine up wrong the first time after installing a motion pro twist throttle, it would start and idle great. you could even run it all the way up to the rev limmiter and let out on the clutch and it would just die. remove the two wires from your throttle housing and try hooking them together and see if that helps, if not, try leaving them apart.

 

i think to check the timing all you have to do is make sure all the timing marks are lined up at the same time.
someone correct me if i'm wrong but as far as i know the only thing you gotta do is make sure your mark on the cam holder/cam holder and cranshaft/case are lined up at the same time.

 

Thanks for the input im going to adjust the valves and while im in there ill go ahead and check the timming. im going to replaced the spark plug and charge up the battery. thanks again for the info ill let you know how it goes and what fixed it. gotta get it fixed race this weekend!!!

 

probably...like some have mentioned.... a TPS issue...

what 'can' happen.....is if when you originally install the throttle cable onto the carb.... you need to make sure you only keep a LITTLE bit of slack in the cable in order to adjust the idle in/out slightly.... if you leave TOO much slack... by screwing the throttle cable IN too far onto the carb... what happens is when you 'crack' the throttle...you have to have TOO much throttle input before the slide can begin to move...and this throws off the TPS....it is 'sensing' a LOT of movement in the thumb throttle... but NO movement in the slide... if this makes any sense....

jmho....Greg

 

You find the problem at 08 trx450 and I have the same problem

 

Do u find the problem ?