250f starting (or lack of)

[xrsforever]

had the opportunity to borrow a friends 250F for the weekend.First I could not start the bike,I had the choke & gas on ,no throttle,kicked at TDC.I was about to give up when after 15 minutes of sitting:I turned gas on,& used no choke. The bike started within three kicks thereafter all weekend. Every bike is different,just my experiences on this one. Oh,and I was impressed with the smooth easy power.:cool:

 

[thump chump]

final resolve....

I have changed my pilot to a #48 (I believe it is this- or it may be a #47), and the air screw is at 1-1/4 turns out. After sitting for two days, and then theroughly washing it, changing the oil and putting a fresh oil filter in it, I kicked through using the compression release about 10 times then tried to start it with the gas and choke on. It started on the third kick. HOWEVER, I live at the beach, where it is ALWAYS 70 degress, and I race at Glen Helen, which seems to be like alwwys 100 degrees, so some fine tunine adjustments may be required.........

More will be revealed......


Thanks to everyone for the suggestions and reccomendations.

 

[JuliusPleaser]

Hot Start? NOT Start!

I just got home from the local practice track, and encountered the same prob i had last time I rode my YZF.

My bike starts 2nd kick 99% of the time. It has a lean miss once it reaches operating temp, but it's not so bad that I can't ride aroud it. I never have any trouble starting it, unless I bobble and kill it on the track. Then I can kick it for days and get nothing. It's happened twice, and both times I've been on the far side of the track. The first time, I had to prop the bike up against the starter's doghouse and stagger back to the truck for liquids.

This was only slightly less embarrassing than wetting one's pants in public.

Tonight, I sat on the bike for 10 minutes (after kicking myself into a semi-coma) and the *&%##%&* fired up on the second kick. I rode about 20 feet before it sputtered to a stop. %&#@^*!!! Some IDIOT forgot to turn the gas back on! Incredibly, it fired up on the third kick, and I rode it back to the truck.

I tethered the &%$&*@ to the truck, and unlocked the door to grab some Gatorade. I sat down on my tailgate to ponder the meaning of life, and inadvertently sat on my alarm remote. Of course, my alarm went off, and when i reached for my keys, I knocked them off into the tall grass my dumb*** had parked in.

By the time I found them, no fewer than 3 smart*** @#^%$&s had walked by and said "Hey man, your alarm's goin' off."

NO %$#& , Sherlock!!! None of them could hear me, though, coz I was on my hands and knees lookin' for the @%&* keys.

I'm sitting here now - half hoping that I've imagined the whole thing. What should I do about my lean condition?

 

[thump chump]

lean condition

I had a YZ400 that would "pop" when I shut off the throtle when I rode it. I am presumiing that you have the same problem. I simply went 1 step richer on the main jet until the "pop" disappeared. Have you ridden the bike in cool or cold weather? And if so, I would imagine that the "pop" would be much worse.

 

[Yamamoto]

Starting your YZ 250F

If your 250F is hard to start when it's new or after some carb maintenance, the idle speed may be set too low. Here is an initial setting you can use to get the thumper started. (Be sure to adjust idle speed to 1700-1900 rpm after the engine has thoroughly warmed up.

The initial idle speed adjustment can easily be reset by performing the following procedure:

1: Remove the black dust cover from the left side of the carb so you can see the throttle stop and throttle pulley.

2: Turn the idle speed adjustment knob counterclockwise until the throttle stop no longer contacts the throttle pulley.

3: Turn the idle speed adjustment knob clockwise until the throttle stop just begins to contact the throttle pulley, and then turn the knob clockwise 5 turns.

4: Reinstall the dust cover.

5: Follow the starting procedure listed in your owners/service manual (YZ250FN is LIT-11626-14-46 and the WR250FN is LIT-11626-14-49) to start the engine.

6: Thoroughly warm the engine and set the idle speed at 1700-1900 rpm using an inductive tachometer.

 

[JuliusPleaser]

My F pops and stalls when I snap the throttle open at about 4-5K revs. It always dies in the same section. It's supposed to be a double-double-double that I see as six singles.

I've been afraid to play with the pilot, idle, etc., coz it's so good about starting most of the time.

Guess i'll bite the bullet and dive in.:eek:

Thanks for the tips.

 

[thump chump]

baby steps

Just remember to make one adjustment at a time, and in small increments, all the time documenting your changes. It will either get better or worse with each change. But you will also always know where you came from.

I think it is second nature to 4-strokes to have a bog when the throttle is snapped off of idle. I've never been able to jet around that and really don't believe that you can. Just hesitation......

I would try richening up the pilot first to see if can notice a difference. The next step would be richening up the needle clip. The owner's manual is pretty good about showing you if you are uncertain.

 

[ThumpinByYou]

yeah my F does the same thing... It pops when I let up off the throttle?? but after it warms up for they disappear. I have also noticed it pop when warming it up just after I kick it with the the choke out. the few times I have started it with the choke.
the pop is from it running to lean? I was listening for pings.

JB

 

[thump chump]

pop pop pop

....it is from being too lean. But if it goes away after the bike is warmed up, I wouldn't be too concerned. It may make your bike a little harder to start, but that's about it.

I ended changing the pilot and air screw to get my 20f to start without pushing it. What a difference. The previous owner had completely jacked with the settings. :scream:

 

[thump chump]

valves...

...complete rebuild in the next 3 weeks. I am going to have to rebuild the bike. It's running fine, but I est that there is probably around 30 hrs on it. And I can tell it is down on power. And while I have it apart, I'll go ahead and rebuild the crank. I have been able to jet it so it will start. The problem is that I live at the beach. It is ALWAYS 70 degrees. But I race at Glen Helen, which in the summer tends to ALWAYS be 100 degrees. I don't want to be fiddling with my bike trying to jet it on race day. I have a couple of weeks off coming up soon, so I am going to rebuild it, check the valves, go ahead and have the suspension stacks replaced, and paint the frame while I'm at it..... And when I'm done I'll spend a practice day trying different jetting to ease the starting problem.

 

[ThumpinByYou]

thanks TC... I solved my pop problem. I noticed it really bad when I had the hot choke pulled, but that would make sense since the hot choke leans out the mixture. I rejetted richer and it starts and hot starts easier now.

JB

 

[ThumpinByYou]

damn it... I spoke to soon. I still get a lighter pops , but only when I snap the throttle off a high rev, and the pops occur at a lower RPM. gonna mess around with the main, pilot and needle jets. I'm going to have to jet richer for fall anyways with the decrease in temperature and humidity

JB

 

[HONDOGGIE]

YZ250F STARTING

I was having the same troubles , the only way to start was to bump it.The choke didn't work, jetting was good , carb adjusted, still nothing. After adjusting the valves it fired up dead cold after sitting 3 days on 2 kicks! I f you haven't adjusted your valves after break in you might consider doing it -

 

[DougRoost]

I was about to say this sounds like a classic case of valves out of adjustment. Specifically, sounds like the exhaust valve lash may be off, staying open too long. Check the clearance, since if this is off carb jetting is pointless.

 

[BikeDstroyer]

DougRoost has a very good point, A good indication that your valves are too tight is hard starting. If your carb adjustments are correct and you are having a hard time starting then you better check your valves.

 

[DougRoost]

The popping was the give-away to me. And of course you never mess with carb jetting until you're sure the bike is sound mechanically. A compression check would be a good idea as well, but first the valves have to be set correctly for this to be accurate.

 

[ThumpinByYou]

yeah thanks... I turned the pilot screw back to the stock position. except now it is completely dying on me when I snap the throttle from idle. I'm going to get the valve clearances checked. then jet from there.:( :( :(

JB

 

[thump chump]

more work-

I was planning on tearing it down for a complete rebuild after this weekend.I will win my class this weekend in this series I have been competng in. I will ptting in a whole new top end and checking all my clearances. I spoke with someone at Big Gun and they mentioned that they will have new valves and cams very shortly. I am hoping that I will be able to get these in short order, and will post comments after I get the chance to test them.