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2004 yz250f jetting?

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I have a 2004 YZ250F. It used to start right up but now it kind of takes a while:bonk: It starts better with the choke off. When I have the choke on and try to start it, it will almost never start. It takes about 10 kicks to start. I was wondering if this is a jetting problem or something. It would be great if you could give me some advice. Thanks!

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I have a 03 yz250f and have been battling starting issues for almost a year. My valves are all dead on. I swapped out all the jets with brand new ones, changed plugs. 10 months later I realized that I moved the needle clip to lean it out and help with the low end bog right around when this issue started. Tonight I hope to throw the clip back to the middle groove.

I'm completely new to carburetors so its a slow learning process, mixed with lots of frustrating days. I know one thing people always say with starting issues is to check valve clearance, and then replace you pilot jet.

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What do you think of your yz250f? Have you had a lot of problems with it or do you think it was a good buy?

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Needle has nothing to do with starting.

It cant be:

Valves (esp. on a bike with a lot of hours) only if hard starting when cold (room temp)

Clogged pilot, but that would have no idle

Mis-adjusted fuel screw

Stuck hot start

Old spark plug

Wrong starting technique

And thern there is a bunch of obscure items.

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Needle has nothing to do with starting.

It cant be:

Valves (esp. on a bike with a lot of hours) only if hard starting when cold (room temp)

Clogged pilot, but that would have no idle

Mis-adjusted fuel screw

Stuck hot start

Old spark plug

Wrong starting technique

And thern there is a bunch of obscure items.

Not what I wanted to hear...

-Valve clearance is good, but yes more difficult when starting cold.

-Checked that the hot start worked properly last night when carb was apart.

-Fairly new PJ (#45, this is what was in there from previous owner, running PC Ti header & Silencer).

-New Iridium spark plug.

-I've had to change my starting technique from finding TDC and one smooth kick no gas, to something more like a worn out 125cc to get her to start (ie lots of quick kicks with a small amount of gas). I can sit all day long with the smooth kick & no gas technique and never get anywhere.

I am very new to all this stuff and learning on the fly, so please bear with me.

I did replace the AF screw with a dial one, this may be my issue, old screw was 1 3/4 turns out, new AF seems to start better at 2 1/4 turns out. I did change the needle clip back to the middle (what it was) last night. I also noticed that my dumb a** put the accelerator pump diaphragm in upside down, but this shouldn't affect starting (I don't think). Finished late last night and haven't had a chance to button it all up and try.

My next step is going to put the stock AF screw back in at 1 7/8 out and see if that changes things. I'm really thinking of getting a KTM where I can just push a button.:thumbsup:

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What do you think of your yz250f? Have you had a lot of problems with it or do you think it was a good buy?

I came from a 125cc, so the power of a 250 4T is amazing. The only issues I've had are self induced. Before I started tinkering with it, the only things all I had done was the basic maintenance stuff (oil, filters, chain/sproket, tires, fork seals). I don't ride to hard, I just like to have a smile on my face at the end of the day. So yes it was a great buy and I'm very happy with the bike, just need to figure out these carburetors.

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Was the new fuel screw an alloy one or a Brass/Stainless one? Did you try your original brass screw?

AP should have no effect on starting.

Do you press the kicker through or do you shove it? It should be a gentle, increasing pressure movement, not a stomp or fanning.

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

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AF screw is the Tusk one, I'm assuming alloy not brass, I'm going to try what I've got today, then put the original brass one back in if it doesn't work out (which it probably will not).

I use to push the starter through with a smooth constant kick. But ever since I started having issues, I've changed the game plan.

I've tried this FS/PJ setting a few times, but I now realize that I have been doing it wrong. My ADD kept me from retaining the last two sentences. I usually adjust the AF then fine tune with the idle, it should be the exact opposite :thumbsup:.

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Thanks for the input on the bike. I like it a lot too! Good luck with your bike mines been good to me so far (only 3 weeks) haha.

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Bringing back a dead thread....

I followed Williams tutorial to the tee adjusting the idle screw, and then the air screw. I was able to start my bike 4 times yesterday on the first kick. I found a new way to kick the bike, and it has really worked great thus far....I pump the kick starter two to three times, then find TDC and give it one kick. I'm so excited right now I might cry. Now to go for a ride tomorrow and see if I really fixed the issue.

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....I pump the kick starter two to three times, then find TDC and give it one kick. I'm so excited right now I might cry. QUOTE]

I call this method "priming the pump" and have been using this method for years. Basically, the 1st several easy strokes are trying to fill the cylinder with fresh new charge and then a much firmer kick to fire her off.

It works like a champ for me.

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