YZ 250 will not start

Coach529
Posts
396
Joined
4/1/2008
Location
Coeur d'Alene, ID US
2011 YZ 250

Brand new 295cc big bore. 2 hours on rebuild. Did a rejet in the morning before we rode. Started on the first kick afterwards.

Drove to the riding area. Started first kick. Was riding with my kids so I was stopping quite a bit to help them, etc. Probably started the bike 5-6 times, no issues.

Stopped at a little turn track to watch my youngest son for 15-20 minutes. Went back to the bike and gave it a kick. Nothing. Weird. Kick for 5 minutes or so, nothing. Replaced the plug. Nothing. Unhooked kill switch. Nothing.

Brought the bike home. Pulled the pipe and looked up the cylinder, all looks fine. Pulled flywheel to check woodruff key, all fine.

No coolant loss. No visible leaks and anything suspicious.

Tested all electrical components. All within spec except for Coil. Spec is .2-.3, tests .4.

I have spark, but it does not seem very good.

I did not check compression, but it takes a healthy boot to kick. It also ran absolutely great prior to me parking it the last time. I did a couple fast laps and it was amazing.

Put a little gas down the spark plug hole and kicked it over. Nothing except it backfired every 4-5 kicks.

The ignition cover gasket was screwed up in one hole, so under the cover had some grit in it. Not sure if this screwed up the stator.
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Paw Paw 271
Posts
3639
Joined
4/3/2013
Location
Benton, LA US
3/7/2021 6:46pm Edited Date/Time 3/7/2021 6:47pm
Did you load it up with all that slow riding with the kids? If so, you will need to clear it out first. You said you rejetted, so the question has to be how do you know the new jetting is correct? Did you a chop test? What did the plug look like after the chop test?
Weak spark? Do an ohms test of the coil as you should have a bright Blue spark at the plug.


Paw Paw
Coach529
Posts
396
Joined
4/1/2008
Location
Coeur d'Alene, ID US
3/7/2021 7:22pm
Did you load it up with all that slow riding with the kids? If so, you will need to clear it out first. You said you...
Did you load it up with all that slow riding with the kids? If so, you will need to clear it out first. You said you rejetted, so the question has to be how do you know the new jetting is correct? Did you a chop test? What did the plug look like after the chop test?
Weak spark? Do an ohms test of the coil as you should have a bright Blue spark at the plug.


Paw Paw
No it was not loaded up. I hammered a couple laps on turn track prior to parking it.

Jetting is really close, plug was light brown when I checked it.

Ohm test of coil was mentioned in the Original Post.
Paw Paw 271
Posts
3639
Joined
4/3/2013
Location
Benton, LA US
3/8/2021 5:53am
Sorry I missed that. So the coil shows to be bad?
Have you cleaned the coil mounts and checked the plug wire?

Paw Paw
Coach529
Posts
396
Joined
4/1/2008
Location
Coeur d'Alene, ID US
3/8/2021 7:41am
Sorry I missed that. So the coil shows to be bad?
Have you cleaned the coil mounts and checked the plug wire?

Paw Paw
Yes I cleaned all grounds and check plug cap and wire.

The Shop

3/8/2021 8:34am
Might try hosing out the stator area with some contact cleaner then blowing out with air.


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