Dirt bike won't start

[Marauder]

Wasn't sure if this was more Dirt Talk or Bike Tech. Can't get my YZ250F to start. I have fuel and I pulled and cleaned the plug. Weird thing is that I didn't have to decompress after several start attempts. Usually I have to hit the lever after 6 or 7 tries. Today, I kept kicking it over and over until I could kick no more; never needed to decompress. Any suggestions?

[Bashed]

You sure you have spark?
Sometimes a new plug is in order.
Even if you cleaned it.
Try a small shot of ether SP.
That will let you know right away.
Damn 4 strokes taking over.
Might see you Saturday afternoon.

Later Bash

[Bueller]

How old is your fuel? Make sure it is fresh, these things hate old gas.
Generally don't foul 4t plugs, is the plug wet? Do you smell fuel? Turn off gas, drain float bowl, kick over several times to clear out.
Do you have decompress or hot start or both? check and see that decompress is releasing, you should slowly kick until you stop at the compression resistance then pull comp release and move engine just past TDC, release then kick a full stroke.

[Marauder]

You sure you have spark?
Sometimes a new plug is in order.
Later Bash

Just replaced the plug 7 months ago. Have only started the bike twice since.


How old is your fuel? Make sure it is fresh, these things hate old gas.
Generally don't foul 4t plugs, is the plug wet? Do you smell fuel? Turn off gas, drain float bowl, kick over several times to clear out.
Do you have decompress or hot start or both? check and see that decompress is releasing, you should slowly kick until you stop at the compression resistance then pull comp release and move engine just past TDC, release then kick a full stroke.
Fuel is not fresh...I will throw a couple fresh gallons in. I do smell fuel and see a bit on the floor. I will drain the bowl and try that tomorrow. I have a decompress lever and a hot start button. Decompress is releasing because it is even easier to kick when it's engaged. Just seems like the bike isn't building the same amount of pressure it used to. I will try what you've suggested tomorrow and report back. Thanks for the advice.

[rforsythe]

Where is the fuel on the floor coming from? Could be overflowing the carb if the float needle is worn out or not seating.

Verify you have spark though, just because it's hooked up doesn't mean you do.

[Bueller]

The fuel on the floor is probably just the float bobbing up and down when he is kicking causing the needle to open and flood it out, if he had a bad seat it would leak constantly, hense the drain float bowl, suggestion. If the plug is wet it is probably fuel fouled, but alway good to check spark (eliminate the simple stuff first).
A lot of these carbs have the floats set wrong, and this is something that should be checked next time the carb is off.

[The_Jackel]

She should start If you have fuel, spark and your timing and kicking is correct, with new plug and fresh gas. If not they can be real finiky. When you first go to start if you can bump up your idle speed just a hair(not much at all) with gas on and full choke open and close the throttle fully
5-10 times. Then kick the proper way and she should start right up.

If it doesnt the most common thing is valve wear due to not cleaning air filters. With all these new coatings your "suppose" to clean your filter every 1-2hours of riding. good luck!

[mayhem]

sell it and get a 2-stroke...............:):) damn 4-chokers......

[dchd1130]

A lot of things can keep it from running. My first guess would be your fuel is bad, if it has been sitting awhile. First thing to do is a compression check and a spark check. If they are both good then that leaves you at fuel. It sounds like you may not have compression though since you don't have to pull the release. So possibly a valve problem. One of the valves could be stock open (potentially because of the fuel).

[Marauder]

Ok....so to test your knowledge, here is what I did:

1) Removed the tank and spark plug. Just a pit of fouling but the plug. It was just installed 7 months ago. Replaced the plug and checked the connection. Good to go.

2) Removed seat and checked air filter. Was cleaned 7 months ago and hadn't been ridden since. Still clean, still lubed. Good to go.

3) Filled the tank with almost 1.8 gallons of 91 octane; shaken, not stirred.

Tried to kick it over...still nothing. Discovered the alan-head screw near the fuel line (remember...still a newb). Placed bucket under drain tube. Left fuel switch on and loosed screw.

Now, I have had many pissed tests in my time in the Army, but it was never that golden. Drained a bit, shutoff the fuel valve and tightened the screw when flow reduced to a drip. Turned fuel back on, mounted and it fired to life on the second kick.

Conclusion: pumped gas sitting for 7 months with no stabilizer.

Lesson learned.

Thanks to all the Bike Tech faithful for your responses and patience.

[rforsythe]

Cool! See you tomorrow then. :D

[Marauder]

Cool! See you tomorrow then. :D
You will if I can cut this new lower roller screw that came with the kickstand. No hacksaw, no grinder. Anyone in Aurora that can help a brother out? I'm soooo close to being ready!

[rforsythe]

Worst case just bring it with as-is along with whatever else you need to attach it, and we will do a little trailhead hacksawing tomorrow.

[Marauder]

Neighbor Gary had impeccable timing...and bolt cutters. Screw fits...moving on to sticker placement.

[rforsythe]

Damn, I was looking forward to busting out the dangerous tools. :twisted: