YZ 250f 09 H*rd to start

[jb1164]

Hi , this is my first post so bare with me.
I've just bought my son a yz 250f 09. I live in the UK but the bike is an imported US version. According to the manual there are differences in the jetting . The idle/pilot jet is a #42 whereas a UK bike would have a #45 and the needle a NHKR-4 whereas the UK spec is NFLR-5. I've not touched the carb setup.

It's a pig to start ! - bring back our YZ125!

(I haven't been able to run it in yet and it's only been started in the shed.)
I've tried the perscribed method to start it from cold.

Choke on - no throttle - get max compression and give it a good kick. (This worked great on an 06 yz250f we borrowed - 2 kicks and it started no problems)
After a constant 5minutes of kicking it might start - or not.

I've tried no choke - no throttle . The bike gradually gets closer and closer to starting until it will sart after a couple of minutes but won't idle. If I keep kicking I can get it to the point whereby it will sart and run. I can then pull the choke out and the engine picks up.

The air temp is 4/5c - 39/41 f at the monment and I'm at sea level.
Help!!!

ps It's got a pro circuit ti4 exhaust fitted

 

[Chili]

When the temps were that low we would usually give the throttle two slow blips to get some fuel moving, then put the choke on, hand off the throttle and kick. My sons 07 RMZ250 fired up first or second kick with that method and it's also proven successful on his 09 KX250F.

I know when we first switched from 125's to 250F's I was ready to torch the thing everytime I had to start it, it will get better as you get more accustomed.

 

[_JOE_]

Your bike is too lean. The pilot is likely a couple steps too lean. Try turning the fuel screw out half a turn, then do as Chili says, two blips of throttle(this shoots a charge of fuel throught the accelerator pump to prime the engine), choke on and roll it around till you hit the compression stroke. Mine won't ever stay running the first attempt when temps get below 40F. I give one throttle blip before the next kick and it always stays running.

When I got mine it was a real PITA to start, too. I dropped the pilot one size to get the fuel screw set at 2 turns out in the cooler weather.

Good luck!

 

[jb1164]

Is turning the fuel screw out enough on its own or should I change the jet as well?

 

[oldguy]

first of all make sure you are getting fuel to the carb by leaning the bike over until fuel comes out the tubes. If it will not start after this it is a good chance your idle is also set to low. We just did total rebuilds on a YZ250F and a YZF450. Both bikes would not start and only give an occasional fart. My son raced both bikes and we knew jetting and fuel screw were set right. I turned the idle out a couple turns and both fired on their second kick. once warmed up we set the idle to where we wanted it and since have not had any trouble getting them to fire on first or second kick.

We use the throttle blip even when warm outside for the first start of the day jsut add a couple when the temps are dropping.

 

[_JOE_]

Turn the fuel screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle. Turn the fuel screw slowly in, and then out, until you find the point where the idle is fastest. If your fuel screw is less than 1 turn from closed, you need a smaller pilot jet. If it is more than 2.5 turns from closed, you need a larger pilot jet.

 

[SpDyKen]

It's a pig to start ! - bring back our YZ125!

No truer words have ever been spoken!





(Sorry guys! Couldn't resist) ;) :debil: :nod: :laugh:

 

[jb1164]

Turn the fuel screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle.

Is this the fuel screw as in the screw underneath the carb in the most inaccesable place ever ?

I've looked at it and to get at the screw looks like I'd need to tilt the carb which means loosening the clamps and taking the seat and petrol tank off.

Am I being useless here or is there any easy way to do this with the bike in running order ?

 

[_JOE_]

There's a bunch of options for aftermarket fuel screws that allow easy access for adjustments. They stick down further and have a larger head so you can turn it by hand. The factory one is dang near impossible to get to.

 

[biglou]

Is this the fuel screw as in the screw underneath the carb in the most inaccesable place ever ?

That's the one, lol!

You can make your own short screwdriver by hammering a nail flat and grinding the end square, then cut it to overall length to fit in the small space provided. It will work until you get an aftermarket screw.

 

[jb1164]

Hammer , nails sounds like my sort of repair ...

Aftermarket screw sound a good idea though.

Any ideas about the needle . I've got a NHKR-4 whereas the UK spec is NFLR-5.

( I don't know if the NHKR is richer or leaner than the NFLR )

Should I be looking to change this once the bike is starting OK?

 

[digifox]

ADMIN EDIT: If you can't offer your best guesses without ignorance then step away from the keyboard.

 

[jb1164]

See that's the benfit of superior knowledge....everything is simple.

We bought the bike with the pipe fitted and haven't been able to run it at all since to check it out.
And I'm not very good at mechanics.
And thought one of you might be able to help without laughing at me .
And it's nearly christmas so be charitable. lol

 

[_JOE_]

The needle will tell if it's wrong. Once you get the pilot worked out and start riding, make sure the main is close then experiment with needle clip position. I use a slow roll on the throttle in 2nd gear from low speed to feel the difference in the midrange. I went 2 clips at first just to make the difference more clear. That's the beauty of a 4t, you don't have to worry about a lean a/f mix seizing the motor. You can feel free to experiment all you want!

 

[jb1164]

Don't fancy a quick trip to the UK do you to sort this out for me?

 

[_JOE_]

It's much easier then you think. Everyone is always very intimidated by jetting until they do it once or twice. Once they see how much better the bike starts and runs they become a bit more comfortable with it.

This thread is worth a read before you start.....http://www.dirtrider.net/forums3/showthread.php?t=159938&highlight=spanky's+jetting+guide

Between that and the info in this thread you will be able to easily get that bike running like a top.

 

[jb1164]

It's much easier then you think.

You were nearly right! Having taken off the tank, saddle and bracket that clamps the frame to the engine head ( to twist thecarb enough to get at the bottom , the sprocket guard ( to get access to the furthest bolt on the bottom of the carb) , removed the bottom of the carb, taken our the starter jet (because the diagram in the manual is wrong) and then finally the pilot jet - and then 40 minutes later put it all back..........

IT STARTS FIRST TIME. ONE KICK . NO CHOKE. NO THREATS. NO SWEARING OR GETTING ANGRY. :)

So big thanks to all those who offered advice and to the guy who said I should slap my head for not realising it was set way too lean - you were probably right. :laugh:

 

[Franx]

My 08 is a pig to start in the cold weather too. My fuel screw is out 2 turns and I just roll the motor over about five times, pull the choke and blip the throttle and it usually fires right up..this works for me when it a degree or two over freezing here.

 

[flyingfuzzball]

IT STARTS FIRST TIME. ONE KICK . NO CHOKE. NO THREATS. NO SWEARING OR GETTING ANGRY. :)

Congratz!!!!

 

[jb1164]

Just need to get the correct needle sorted out. Is it a major drama getting the top of the carb apart?

 

[_JOE_]

Glad to hear you got it starting better. Chances are you're too rich now, though. You should have to use the choke to start a cold engine and the hotstart to start a hot engine. The throttle response will slower of idle. This is a pretty easy way to get the fuel screw in the ballpark, once you get it hot kill it and try to start it again. If you're too rich it will be a b@stard to start. The hot engine needs a lean mix to light off, hence the need for the hotstart. It should fire right up if you lean the pilot out a bit.




As for the needle......There's a small cap with two allen screws on top of the carb. If you pull the tank and seat you should be able to get to it. On mine I have to twist the carb to clear the frame. Once the cover is there should be another allen screw down inside the carb. If you have someone hold throttle wide open it's easier to get to. Once that's out you can get at the needle. My bike came with a tool that I was baffled by, until I decided to try to pull the needle out. It is a piece of wire bent in a loop on one end with a little rubber tube on the other. You slide the tube over the top of the needle and pull it out. Otherwise a small pair of needle nose pliers would work.

 

[jb1164]

My bike came with a tool that I was baffled by, until I decided to try to pull the needle out. It is a piece of wire bent in a loop on one end with a little rubber tube on the other.

So that's not for cleaning your ears out .

OK - thanks for all the support. :cool:

 

[jb1164]

I've just finished adjusting the fuel mixture. I bought an aftermarket screw and it's made life loads easier. Having followed the carb set-up suggestions the screw is now just further than 1 1/4 (1 3/16?) turns out with a #45 idle jet as opposed to the factory set 2 1/4 with a #42. It did occur to me that when I did the initial jet change a couple of nights ago that I had a heater on in my shed and this may have had an affect when starting the bike so I think I'll still need to try it at different times of the day to see if the temp. makes much difference.

Just the needle to go now but hopefully this had sorted out the starting problems.

 

[_JOE_]

You shouldn't have to move it much to compensate for day-to-day temp changes. Mine usually stays within a half turn for most of the season. Our temps are usually between 45 and 75 degrees. I would go a size bigger in the winter if I rode more. I just run the pilot out about 2 turns as it is. I've heard of guys having issues with the fuel screw falling out from not enough spring tension at more than 2 turns.

Do you have somewhere you can go ride the bike? You might want to experiment with the main to see if it's close, if it's way off it may effect your needle position. You don't want to mess the needle any more than you have to. The main is a snap to change. All you have to do is turn off the gas, drain the float bowl, loosen the 17mm cap on the bottom and insert a 6mm socket onto the main jet. If you crouch down and look up into the carb towards the front you should see a brass hex about 15mm long, that's the main. You may get the tube with it, if so you'll need to be careful when reinstalling so the needle drops in as you push it up. You can have a buddy hold the throttle open to make this easier. Just do some full throttle runs paying attention to how the bike pulls and revs out in the top end. You should be able to tell right away what effect you had. If you have a few jets on hand you can set the main really quickly.

 

[jb1164]

Sounds like good advice - it bugs me though what a pain it is to set the carb up on the 250f, everything was nice and accessible on the 125.

Just out of curiosity though do you get set ups that overlap with the idle jet. i.e.
a #42 set really rich would be similar to a #45 set lean.

With the main am I looking to go bigger as it gets colder and then back down again in the summer?