Oh, Come On! I Changed The Main Jet On My 250 And Now It WILL NOT START!!!

[Aufgeblassen]

Originally Posted by TominMO

. I wonder if the fuel or air mixture screw is turned all the way in.

If it was, it never would have started from the get-go. It worked fine up to about 40 MPH, at which time I had to partial to fully put choke on, especially to accelerate, or else it would stumble.

And no, I did not touch the air/fuel mixture screw one iota.

[China Rider 27]

I would verify you have spark. Verify you have gas to and in the carburetor. Then I would take that carburetor apart again and go over it with a fine tooth comb since it worked before it was disassembled. Verify the slide works properly on the bike with throttle cable. Verify the float and needle is not stuck. Float level is correct. You should be able to hear the float move back and forth when moving it off the bike. I have had carbs would not start the bike put back on after cleaning because the slide was not open enough to allow some air at start up (idle speed screw was not adjusted correctly). What kind of carburetor is it?

[mototech77]

Originally Posted by Aufgeblassen

If it was, it never would have started from the get-go. It worked fine up to about 40 MPH, at which time I had to partial to fully put choke on, especially to accelerate, or else it would stumble.

And no, I did not touch the air/fuel mixture screw one iota.

I have to agree with what someone else said on here earlier. I’ve seen a lot of threads where you ask for help, then when people try to help you, you come back with some snarky comment. Why is this?

I may be misunderstanding your intentions, though, as I get misunderstood at times as well.

[TominMO]

Diagnosis plan.

FAST:
Fuel
Since "It worked until I fixed it", i.e. it ran previously, this is by far the most likely issue. Changing a main jet would not prevent it from starting, so something else has also changed, and very likely inside the carb. Also of course: petcock on, clean fuel filter, supply line not blocked. IE gas has to get to the carb and through the carb. Also make sure no jets or ports are blocked; a little bit of dirt in the pilot might have done you in.

Air
Hardly ever the problem unless fuel/air mixture screw all the way in, or too far out.

Spark
If you pull the plug, ground it against the motor with the plug wire on it, and hit the start button, you should see a healthy spark. If you have that, then it is fuel related. I would in fact start the diagnosis with this, to quickly rule out a spark issue so you can move on to fuel. If no spark, check for any loose electrical connections that would involve ignition, including plug wire on plug, and the plug gap.

Timing
Probably not an issue in this case, since all you did was carb work.

Of course it is still possible to have two issues, fuel and spark. Or two issues inside the carb.

[Aufgeblassen]

Originally Posted by mototech77

I’ve seen a lot of threads where you ask for help, then when people try to help you, you come back with some snarky comment.

A LOT? Huh? I am very new here! You must be confusing with someone else.

[FlyingBasset]

Originally Posted by Aufgeblassen

A LOT? Huh? I am very new here! You must be confusing with someone else.

No dude, it's definitely you. You have 70 posts even though you've only been here a month - so you're obviously commenting a lot in a very small forum full of knowledgable people. That's why when you make false statements like "110 is 110 so it doesn't matter" it stands out.

It's not a big deal, but I do think it's funny that even when multiple people point out you're being abrasive your response is "No, they must all be wrong, it couldn't possibly be that I'm wrong!" Very ironic.

Anyway, glad you got it figured out.

[gwowzer]

P.S. it doesn't take any cranking to get gas in the carb... it's gravity fed hence why you have a float and bowl lol

[Aufgeblassen]

Originally Posted by gwowzer

P.S. it doesn't take any cranking to get gas in the carb... it's gravity fed hence why you have a float and bowl lol

In order for fuel to fully fill the carb, AIR must be removed. The cranking eventually removed the air so engine could run.

[J4Fun]

No, you were cranking before the bowl was filled! And that is what caused the problem!

[JerryHawk250]

Originally Posted by Aufgeblassen

In order for fuel to fully fill the carb, AIR must be removed. The cranking eventually removed the air so engine could run.

As stated before the carb is gravity fed. The bowl is vented so air is removed as the bowl is filled. But the again you could of have a stuck float which didn't allow the bowl to fill at the time. You got it running so no need for anything else to be discussed.