Jetting or Valves?

Hi All,

My son picked up a very low hour (approx 25 hours) 06 250X from a friend of mine who bought it new back in 06. Its in great shape except for the cold starting issues. Its a 49 state model with the air box lid removed and stock pipe/silencer/SA.

I rejetted it richer for the cold Idaho winter temps:

150 main

45 pilot

Has a Twin Air filter

I know these bikes can have valve issues (had an 05 CRF450R) and have not checked them yet. Yesterday I ran the battery to empty and had to then kickstart it to finally get it to run. The strange thing is that once I could get it to stay running with the choke on if I gave it any throttle at all it would die. Gradually once it would stay running longer I could get it to stay running then rode it. Also, the idle when the motor is cold with the choke on is very uneven, goes up the down and so on without touching the throttle. Had some backfiring but not excessive. Once warmed up seems to run fine and starts up fine too.

I am no expert with these 4 strokes and jetting them. Elevation here is about 2800 feet. Am I looking at a jetting issue (need to go even richer) or does this sounds more like a valve problem?

thanks Dave

Its kinda hard to say exactly what it is. Is the gas fresh? Air filter clean? No junk in the bottom of the carb has been sucked into that new 45 PJ?

Check the valves...its not hard. Follow the description in the stickly. .005" on intakes. If clearance has closed to zero or close, thats a problem that will cause hard starting.

On my son's bike, his ran ok when the valves were going, but it got harder to start and eventually wouldn't.

The hot start isn't stuck open is it? Where's the fuel screw set? Should probabably be about 1 turn to left..not more than 2.

Just a bunch of stuff to rule out. My guess is the pilot is partly plugged. Pull it out and look through it. I gave up on trying to clean mine when it got something in it and just got a new one.

my guess is the valve clearences are out of spec, same thing happened to me last spring and this spring. i shimmed them and now it starts first kick and idles smooth unlike before. also try putting new fuel in it depending on how old it is. but check the clearences. if they are out then its a 10 dollar fix if you do it yourself. if they are good then its prob carb.

Yesterday I started the bike. Started on the first kick! I am going to richen the needle one notch as there still is some bog at smaller throttle openings before the motor is fully warmed up. Fuel screw is set a 2 turns out. This bike seems to not like to start when it has sat for very long.

I'll check the valves when I richen the needle.

Thanks for all the tips,


Try this after its sat and is fully cold and you want to start it.

Turn on fuel, pull on choke, pull clutch lever and hit the starter button for a couple seconds. Stop. (this assures that there is fuel in the carb's circuits).

Twist throttle 2-3 times to WOT. Stop. (this injects fuel into the intake).

Pull clutch, don't twist throttle, and press starter. Should fire up. Might die. If dies, twist throttle to WOT 1-2 times. Stop. Pull clutch, don't twist throttle and press starter. Should start and idle. Might be rough until warms and speeds up.

Let her idle until warmed up, then turn off choke.

Ride her easy at first until fully warmed up.

Hope this helps.


Thanks Dave, I will try your procedure.


Just fyi...We were out yesterday and it was 25 degrees and snowing and my starting procedure wouldn't work. Was trying my son's bike first and I was like...***!!!! Tried mine....but my battery was weak, so it didn't last long and we had to kick it. I finally got my son's running first. Tried every sequence I could think of including holding the throttle wide open to clear it out. Nothing would work. Trick was, while pushing starter and she's close to firing off (actually it was firing a little but not enough to run) crack the throttle just a bit. I did it accidentally and she lit up!

Worked on mine too while kicking.

All the kicking warmed us up anyway!!

Thanks for all your suggestions: I checked the valves and sure enough the intakes have close up all the way, exhausts are fine. My guess is my friend we bought the bike from was not real good about air filter maint and the bike sucked enough dirt to trash the intakes. Since my son does not ride allot (probably 25 hours a year on the bike) with our weather here I am going to have a new piston/rings/OEM intakes/head work for intakes. I know stainless would be better but weighing the cost vs the amount of time my son rides this sounds like the most cost effective way to go. We will also run the stock Honda air filter from now on.

Once you do the stainless intakes, the bike is virtually indestructible. If you don't, then the clock is ticking towards the time you do the valves again.

That is such a good bike once you get it running.

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