YZ250F Won't Start the conventional way

wts1982

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Jun 17, 2001
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#1
I purchased my 250F in back in april. Back then it was hard to start, but I was still able to kick start it after 10-20 times.

I live in NC where the elevation is approx 900' and now that summer is here the humidity is 75%-90%. The only way that I can get my bike to start is to push start it.

The bike is stock and the only things that I have tried to adjust are the pilot screw. I have gone from 1 1/2 to 4 turns out and it still does not start. It seems to run best at 31/2 to 4 turns out. Is this too much? I also tried to change the clip position on the needle jet. When it was at (pos 3) I could not tell any difference, when it was at (pos 5) I did notice that it took longer to decellerate.

I am using 93 pump gas and do have some backfire (or popping) on slowdown. The plug is tan to light brown in color.

This is my first 4stroke and I feel that I do not know anything about this bike so any help ould be greatly appriciated.

I would really like to understand how to get this bike running for my current conditions and then also understand what I need to do when it gets cold and less humid.
 

CRGuy

Posts Too Much
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Nov 14, 2000
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#2
More than 3 turn's is in need of a new pilot. Try the starting drill with the 426.
Okie can help you he's got one that he can start first kick so he should be able to tell you what he does right.
CRG
 

zcookie49

Seven OUT!
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Dec 21, 2000
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#3
My 250F can be tempermental at times.. but not always... If you can get it started, make sure you let it warm up well with choke on. I have found that if you stall this bike while in the warm up process, it is a bear to start, having to drag it to fire...
starting. Make sure you compress out to TDC, then come back up and kick hard.
I went out about 2 clicks on my air screw. this weekend, when it started to rain while riding, the bike would die when i would come to a stop, which it usually doesnt do. after the rain, no problems idiling....
.
I would make sure your technigue for starting is proper . I too came from 2 stroke and old habits still exist. For first initial start of the day, I like to stand on something, i put my left foot on a crate or something. that way you get more leverage and the bike will fire up easier. later on in the rides, I can start no matter what...
I have changed plugs before, thinking that they might foul. be careful not to pull back on that throttle. some people suggest 2 blips of the throttle, this bike has an automated accelerator pump to the carb, so gas is being shot in each kick, too much and you will FLOOD it.. I have taken a plug out in the past after several people were kicking it, in the beginning. the plug was soaked, but no oil on it obviously. I changed plug, still wouldnt kick. had to pull behind 4wheeler, ran fine the rest of the day.. on that occasion, I didnt let the bike properly warm up and stalled it on a gulley.
any other questions or additional info, post it so that we can try to figure it out for you... This bike is awesome, i rode it for 6 hours sat and wasnt really fatigued till the end...BUT when it wont start, I am ready to shoot buck shot at the gas tank, that is how frustrating it can be...
 
Joined
Feb 12, 2001
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#4
wts1982,

do you use the yamaha 4stroke starting drill?

0) engine cold=use choke / engine hot=use hot start button
1) take your hand off the throttle, rest it on brake master cylinder
2) push the kickstarter down gently until it's firm (=TDC)
3) pull the compression release lever
4) push the kickstarter down another inch (5 degrees or so)
5) let out the compression release lever
6) allow the kickstarter to return to the top of it's stroke
7) kick it like you mean it, but NO throttle. never turn the throttle!

some more questions:
when you do get it started, does it idle ok?
does it accelerate up from idle ok without load? with load?

my advice, put the needle back at stock. the needle doesn't affect starting to any large degree. solve the starting problem first, then you can work on the other areas. also, do not "push thru" the hard spot at TDC without using the compression release lever, this will eventually lead to a snapped starter shaft--not the kickstarter lever itself but the round shaft that disappears into the engine. much $$$ to fix this.

the wrooster
ps
my brother has the yz250f and i've got the wr250f. his came set up perfect, i had to fuss with the fuel screw on mine a bit (it was set too rich). for the first few times the bikes are hard to start. but now, after a couple of hundred miles, both start on the 1st or 2nd kick, hot or cold. also, eventually you get used to the "drill" and it just becomes second nature.
 
Joined
Jun 15, 2001
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#5
Hmm, did you turn the pilot screw out 4 turns or the pilot air screw? You have to open the bowl to turn the pilot screw. 4 turns out sounds like alot. You may want to try going in with it from the stock setting and see if that helps. You shold be opening the carb bowl and turning the pilot screw and not the air screw outside the bowl. My bike seems to like the choke on for any not yet warmed up start. The tan plug sounds fine, every one I know that has these bikes says the plug looks tan, so dose mine. Idel fule is all the pilot jet and like Wrooster said, moving the needle really dose not help you durring start or idel. Be carefull with the push starts, 98 YZ 400s had week clutch baskets and that was the A #1 way to explode them. Also, like Wrooster said, dont tuch that throttle or youll inject extra fuel into the thing. The 250 F is kinda like a 125 in that the smaller the moter is the more slight fule settings affect them more. Bigger moters seem to be less tempramental to minor fule problems at start up.
 

zcookie49

Seven OUT!
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#6
jersey

Hey WROOSTER, I see you are in NJ. . I just camped out there this past weekend, I'm sure you've probably been to Port Elizabeth/Millville...We have been going there over the years and recently it has been pretty cool with the rides up there (not getting busted).. You ever hit it up there, I havent seen a WR250f up there yet, but I'm sure to give you a heads up if I see you. I could already tell I'm gonna need a new tire up at that place, with the rains, we had some slop. Later.
 
Joined
May 29, 2001
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#7
I went riding with a 3 month old YZ250F yesterday and I reckon I'd have to say it was an awsome machine. I definately am glad I don't own one as a trail bike though. I was waiting for my mate to throw it on the ground and start stomping on it. Admitedly he did drop it on it's side up a fairly steep pine forested hill. But when your own bike starts first pop after the same thing,and your other mate's WR426 takes only 2 kicks max to fire, you've gotta feel for the YZ pilot. An excellent MX bike by the look of it.
Obee