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Yz250 not starting and bogging.

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I have a 99 yz250. I cannot get the bike to run. If I do somehow get it to start, it wil run for a second or two and bog then die. The reeds are brand new,just put them in. Top end has about ten hours on it.silencer is not clogged, and is freshly packed. Plug is brand new. I atempted to sit the float level to what I thought was correct.when I pull the plug it is wet. So I'm pretty sure I'm flooding. I would appreciate any opinions, or advice. Also does anyone know what the float hight should be on a 99 yz250.

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I couldn't tell you fire sure, but the guy I bought it from did tell me I should rebuild the carb, so I'm guessing it's got some age on it

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When did you last check the air filter?

I had a friend that raced a TRX250R. Washed it after racing it one weekend and couldn't get it to start after that. Had spark, fuel, compression...everything looked okay. It would pop, and try to start but wouldn't run. Pulled the air filter and dummy stuck a rag in the air boot when he cleaned the airbox and forgot to take it out when he put the air filter back in:banghead:

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Lol, I don't think I left one in there, but I'll check. I had the whole bike tore apart so who knows.

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id pull the plug kick it over prolly 20 times hard with the plug out and gas off, then dry off th flooded plug put it in, cap on it, , and thendo this its what i did to my 96 yz 250 when it was doing that, clean both off the jets out in he carb they may be clogged , and possibly you might be a little to rich on the air screw

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Thanks, the carb has been fully taken apart, all jets were cleaned with carb cleaner and compressed air. Im in the process of trying to tweak the carb, but i'm not really sure where to start.

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Have you actually replaced the plug? If it flooded that spark plug is junk. Throw another one in there. Next step if youve already checked carb and made sure your getting fuel would be to check timing. Make sure its set at factory spec.

As far as your carb. the best place to start is factory specs. to get it running, then fine tune from there.

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Thanks, would you happen to know the stock specs? I know the float level should be about 6.5mm. I've no idea what the stock jetting is, or where the air screw should be set.

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MAIN 172

PILOT 48

NEEDLE N3VF

CLIP 2ND

AIR SCREW 1 1/2

Hope this helps.

Also one simple thing you should check before you start swapping out brass, disconnect the kill switch and see if it will fire. They go bad quite often believe it or not.

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Take the plug out and turn it upside down. Take the tank off first. Crank the kick starter and see what comes out. Gas? Coolant? Oil? Nothing? Coolant, bad o ring sealing the head. Gas, flooding, stuck float boal. Oil, bad crank bearing. Nothing, well it does need gas. If I had to make a guess, bad o ring in the head. Good news is its easy and cheap.

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I did this before and i had gas coming out, thats why i believe i'm flooding. I tried seting the float level, but it still did the same thing. Although that was my first try, so i might give it another go.

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Yes just unplug it, dont plug anything back in, unplug the kill switch and see if it fires.

If it were a bad head O ring the bike would still run. It would just be lean.

To check to see if you are getting fuel, unhook the gas line from the carb and turn petcock on. If fuel is flowing you are in good shape. Have you tried grounding the plug to the motor to see if you are getting strong spark? Again I would check the kill switch before going any further since you have been through pretty much everything already as it is the simplest remedy.

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Spark is good, Fuel flow is good also. I guess ill try the kill swithch. I really appreciate all the help. It's killing me not being able to ride it.

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Pilot jet could still be clogged. You should see light through it. Also, when setting the float height there are two springs; the first is very light and only works on the float. The second is a bit heavier and works on the needle. You want to compress the float spring without moving the needle. That's the point for setting the height.

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Well, I got it running. It took a while to get it going. Iset the jetting and air screw setting back to stock. The throttle felt decently responsive when idling. When I rode the bike I could tell it wasn't right. The bike would sputter, backfire and kick in and out of the power band rapidly. after putting around for about 5 minutes I stoped held the clutch in, and it started to bog. To the point where I Peged the throttle and it wouldn't rev up, just boged and died. Any more ideas as to what the problem may be?

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Carb has been fully tore down and cleaned, that's what's blowing my mind. Earlier today I got it running, it was rough though. Cut it off and kicked it back over. Started back up on the second kick. Did this about three times. It noted out and died, wouldn't restart. Later tonight I took the carb off check the floats again. Took a good while, but I got it to start. Now it won't do anything again. I'm lost as far as what to do.

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