i've heard that cats were hard starting - but mine takes it to the extreme.
i've got a 2001 250 2x4 - yesterday (80 deg) when i tried starting, i had to use full choke and cover the air intake with my hand to get it to cough. i did that a couple of times and let it run (still full choke) for 5 more minutes. then, in the course of the next 20 minutes, i could ride it and gradually ease off on the choke until it was fully off.

after 30 minutes, it was pretty much back to normal, no backfiring, acceleration was fine and enough power to climb hills. it gets run nearly every day, so it's not stale gas. this has been occuring for a few weeks, but till now, weather has been cooler.

The needle clip is in the 4th notch now, so it should be running on the rich side already. The spark looks ok whether it's cold or warm. Any ideas of what to look at next?

 

Uffda, I have no idea what could be wrong.
My 400 starts right up, no matter what the temp. Anything warmer then 40 and I don't even use the choke.

 

The needle won't help with the hard starting. You enriching curcuit appears to not work properly or you could have a low float level. Do you run the carb dry after you run the bike? If you move it on a trailer or in the back of your truck after you do this the bouncing of the float against the stop will lower the fuel level. I have found my 2001 250 2X4 start better in the cold weather that the warm. Cold out and give it full choke , hit the starter and it runs. In the warm weather, 50 degrees and up, if I use full choke it will flood. I hadn't hear that Cats were suppose to be hard to start.

 

My TRV had the air vent for the gas tank and a vent hose from the carborator pinched. As a result It was hard startig and would only run for a short amount of time before quitting. I messed with jet screws and just could not get it to work. Finally got he pinched lines figured out and the problem went away.

Then I had to deal with the settings I messed up. I wold check those hoses for blockages and obstructions before taking the carb apart and checking the float. I have found it best to start with the easy stuff first.

 

Another possibility is a vacume leak. Once you get it running, spray WD40 around carb boots and any additional sealing areas in the intake system and see if you get a sudden change in rpm level. You state it runs OK after 20 minutes or so. It might be that the area of a possible leak has expanded with engine / exhaust heat and sealed itself somewhat.

 

that strange that you have to wait 20 minutes to let it warm up, mine takes 5 minutes but course i live in texas it's always hot. check the wire see it it is burned or lose because that happen to me once and it took me 10 minutes to start that dang thing but it was an simple fix. does it shake or rattle?

 

Have you had your valves adjusted? Sounds like the intake side is a little tight, when the valve tightens up it limits the amount of air/fuel that enters the engine. If the valves are ok then your pilot jet has an obstruction, simply clean or replace.

 

I agree with Arctic 375, seems like we have alot of 250 and 300's that need valves set. Hard starting and not idleing till warmed way up are two symtoms that we see alot. Check valves and then clean carb like Arctic 375 says.

 

Thanks - i'll look at the valves -- If the valve clearance is too close when cold - It gets smaller when warmed up? So the intake valve may not be opening far enough? is the cold clearance for the valves 0.003"? i checked the tank vent tube and 2 carb tubes for blockage - they were all clear. plug wire was good also.[img]i/expressions/face-icon-small-confused.gif[/img]

 

Valve/Tappet clearence is intake 0.03-0.08mm (0.001-0.003in)and exhaust 0.08-0.13mm (0.003-0.005in). I would have to assume that is a cold measurement as the shop manual says nothing about warming the motor prior to taking the measurements.