Please help! I recently bought a Yz250f and have not been able to start it, it Has spark, but there are many issues with the carby which I wanna rule out before I leap into a rebuild, ( I want to avoid a rebuild if possible as I’m low on cash). The carby at the moment is a complete mess so the usual steps to fixing it might not work. So here’s the deal with the carb: 

- It’s leaking fuel from overflow ( really fast! ) and when I mean really fast, I mean it emptied my fuel tank in 2 mins.

- It has a slow leak coming from somewhere under the float bowl

- the air fuel screw is not adjusted correctly 

- I don’t know if the electrics work on it either 

- I don’t even know if it’s shooting fuel into the cylinder or not, as after kicking it a couple times and it’s not starting I remove the spark plug and it’s still dry. ( I tried putting fuel directly into cylinder from the spark plug hole but the bike still wouldn’t start) 

okay so I know it’s a lot but I’m not expecting anyone to answer every single question themselves. If each person could tackle whatever problem they know it would help heaps. Also just want to know what Order to fix things in as I can’t do air fuel until the bike is running and it won’t run unless I stop the leaking and get it to spray fuel into the cylinder. And buying a new carby is not an option ( I’ve got $40 to my name atm). Please help guys thanks.

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Gas flowing out the overflow is the float sticking or bent, maybe the float has a hole and has gas in it preventing it from floating. Pull the carb, crack the bowl open and check the float. 

And what color is the spark? Blue or yellow?

Also the cap on the bottom of the float bowl might has a cracked or missing gasket causing the leak

6 hours ago, kamren demarce said:
6 hours ago, kamren demarce said:

Gas flowing out the overflow is the float sticking or bent, maybe the float has a hole and has gas in it preventing it from floating. Pull the carb, crack the bowl open and check the float. 

I pulled the carby to bits, cleaned it for like 2 1/2 hours, the float was stuck, but it was strange I’ve never seen anything like this before, The little fins on the needle are scraping on the seat, the seat is down too deep into the hole so I can’t screw it out. Was thinking about sanding the fins down so it can move freely.

Sorry I would reply to your last message but I am new to this site and don't know how to reply to it or quote it. Whatever y'all call it. But do you have any pics of the needle and where its scraping?

Gas overflowing means the float is misadjusted. You need to take off the bowl and bend the float tab up. If you have your owners manual it should have the proper specs on how to do it. Also check your spark plug. Is it getting spark what color spark if it's yellow or orange in color spark is weak. You want to see a white purple or blue in color spark. Next thing I would do is adjust your fuel mixture screw back to stock. I just did this for my bike because I was having issues similar to you.but now I'm having other issues.

Before adjusting the float, check the float needle. More than likely it is hardened and not sealing so it needs replaced. While you're at it get new orings for everything that you take apart. Pulling the carb apart and cleaning all the jets should be another priority if it has sat long enough to harden the needle valve. Your fuel screw should be 2 3/8 turn from the bottomed out position on it. Also if you don't know when the last time the plug and air filter was changed I'd check it. If you haven't gotten it to start after all that, then you'll have to pop the valve cover and make sure all the valves are in spec

On 24/02/2018 at 0:08 PM, WrAaron said:

Gas overflowing means the float is misadjusted. You need to take off the bowl and bend the float tab up. If you have your owners manual it should have the proper specs on how to do it. Also check your spark plug. Is it getting spark what color spark if it's yellow or orange in color spark is weak. You want to see a white purple or blue in color spark. Next thing I would do is adjust your fuel mixture screw back to stock. I just did this for my bike because I was having issues similar to you.but now I'm having other issues.

Got the float problem fixed the bike is leaking but as I was cleaning the carby I lost the leak jet and the accelerator pump won’t work without it so still haven’t been able to check if it starts 😪. The spark is good, I might have to do a rebuild but want to know what everyone’s views on used pistons are. I see a lot of used pistons on eBay that are in good condition, would it be a bad idea to put one in my bike? 

On 24/02/2018 at 0:48 PM, passthru89 said:

Before adjusting the float, check the float needle. More than likely it is hardened and not sealing so it needs replaced. While you're at it get new orings for everything that you take apart. Pulling the carb apart and cleaning all the jets should be another priority if it has sat long enough to harden the needle valve. Your fuel screw should be 2 3/8 turn from the bottomed out position on it. Also if you don't know when the last time the plug and air filter was changed I'd check it. If you haven't gotten it to start after all that, then you'll have to pop the valve cover and make sure all the valves are in spec

Yeah valves are in spec and had to do timing anyway when checking the clearances so that’s all good. I tried pouring fuel into the cylinder and it still didn’t start so would you say after that that the bike would need a rebuild? Or is it possible that I can still be something else. 

I would get the carb sorted out first then move on from there. There shouldnt be a need to pour fuel in the cylinder that may cause it to flood. Check the boots where carb connects  for tears or cracks that could be an issue aswell. Gotta check the basics first fuel spark air before moving on.

On 3/1/2018 at 10:57 PM, Allooushh said:

. I see a lot of used pistons on eBay that are in good condition, would it be a bad idea to put one in my bike? 

Yes. .  Bad idea. You already HAVE a used piston. Go new or leave yours in it and check specs. #saveup. Fix the carb 1st. It's the heart. 

 

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