YZ250 Starting issues and questions - Am i doing this right...

Yes, I'm a newbie. I bought this bike 2 years ago from a friend for $1500 havent rode it much and worked on it zero time.


So I made a bad mistake, I let gas sit in it for about 8 months in my shed...:thumbsup:

I need some help on getting this back into running condition. I Removed the carb and soaked it in chem dip for an hour. I removed the floats and any gaskets I could get to and the choke push/pull before the soak. After the hour soak I blew out all the holes I could see with high pressure compressor and cleaned any remaining chem dip from the carb. I put it back together and confirmed that I could see gas coming from the small hole in the center of the carb when I held the throttle open and the choke open.

It started on the second kick and ran for 5 seconds and now I can kick and kick and nothing.

Whats my next step in getting this back in running order?

Also is $1500 a good buy for this bike or did I get taken?

From the picture can you tell what year this bike is?

If I have to order a carb rebuild kit what model carb is this?

Is 32/1 ratio with 93 octane the correct gas mix for this?

Hello there

How old is that bike? Anyway if the bike ran for 5 minutes it looks like you don't get fuel to the carb or only a little. How long you have to wait to start again or doe it not start at all?



Edited by arnego2

If it sits too long, you can get old, gooped up gas in the petcock area. You'll need to clean up from the tank on down. You've likely just sucked up some more poop into your pilot jet from the bad stuff already stuck in the system. Thoroughly clean it all out.

I can start it and it runs for about 20-30 seconds now after cleaning it out again. Then after that 20-30 second run I cant get it to start. My guess is that I need to take the carb apart again and blow out the holes?

yu may want to look at the petcock too. the filter in the bottom of the tank could be plugged up. a pair of screws will reveal that. next step will be pulling the jets and running a wire through them.

it will come around soon.

Looks like a '94-'95 to me. It looks clean but I just paid $1500 for a VERY clean 2003... IMO you got taken.

Looks like a '94-'95 to me. It looks clean but I just paid $1500 for a VERY clean 2003... IMO you got taken.

Eh, depending on when it was last rebuilt (bottom end too) that bike looks extremely clean and well taken care of. $1500 may be a little high, but I wouldn't say he got ripped off.

I had the same problem with a yz 125 and it had the same symptoms only ran a little while and then wouldnt start again for a few hours. my problem was a bad spark plug so if you havent already changed it try it out its only like 4$ a plug, make sure you get the right one though

Empty the gas tank, take it off and make sure there's no gel/trash in the tank, look good on the bottom of the tank with a flashlight. If so, then it'll keep clogging the carb until you clean it.

I took the petcock off and inspected and cleaned the bottom of the gas tank and chem dip soaked the petcock and carb again. This time I removed the set screws and found that the screw closest to the pilot jet has small holes kinda like flow holes drilled in the end. This was clogged with gel orange mess....

Needless to say it came out looking new after the dip....I made another newbie mistake though....I forgot to remove the gasket on the bottom bowl nut and the chem dip disentegrated it....Also as I was putting the needle valve assembly back together and broke a gasket sealing this to the bottom inside of the carb.

( not sure what you call this piece but its the part that moves up and down with the floats in the carb and has a small metal cone that opens and closes a hole as it moves up and down )

So I put it all back together and a new spark plug but gas pores out the tube at the bottom of the carb since that gasket is broken.

I'm guessing I need a carb kit now so that I can get this running....Can anyone point me in the right direction as to what model carb this is and where's the best buy for the carb kit?

So what year is the bike? Its nice looking I'm gonna guess mid 90s.

First off stop referring to yourself as a newbie. You have successfully disassembled a carb which is more than most can do. The missing gasket is not causing your overflowing problem. I don't have a bowl gasket on mine, though I probably should. What has probably happened is some more of the gunk has lodged in your float needle valve. First thing you can try is to remove the drain nut on the bottom of the carb, and then turn the fuel on and let some fuel flush through it. This opens the float all the way and any trash will hopefully come through allowing it to seat properly. If that doesn't work you will need to take it apart again and clean the area around the needle and seat in the bowl. Had the same issue about a week ago.

Also even if the carb is overflowing it should still start if you have everything else cleaned out.

Thanks ttugrad95, I'm not sure what year the bike is...

Also thanks for your complements, just wanted to start out with saying I am a newbie out of respect. I'm a new member to this site and new to working on 2 stroke's.

What happened is the float needle valve gasket is screwed up, I didnt get it seated properly and its old and I tried to cram it back together and smashed one side of it. So now it doesnt seat properly and gas just flows out through the side of the seat where the gasket is smashed. Tonight I disasembled cleaned and reassembled it for the 7th time in 7 days :thumbsup: I also goofed up the carb drain nut gasket but I was able to get this back together without leaks. ( my prob is with the needle valve gasket ) can I use any rubber gasket that fits? I think I have a rubber gasket that may fit but its a faucet stem gasket used in a kitchen sink faucet can I use that?

One good thing is I'm getting real good at taking apart and putting this back together...

I'd say your bike is around a 93-94. I think they changed the plastics in 95. I would just go on bike bandit and order a new gasket and a needle valve. Ive heard they wear and should be replaced every couple years. It's going to cost about 20 bucks all said and done and it will be the right way.

I've spent some time on the bike bandit site but I can't find the carb gasket set for my carb. It's a mikuni flatside TM but I'm not sure what mm it is.

I would just get a carb rebuild kit. Its should have everything you need and more.

So to close this out. I bought the carb kit and I'm back to slinging dirt.

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