yz 250 not starting

[HoogiesNgrinderz]

Jay said to post a new thread, which isn't a bad idea at all. I have a 1990 YZ 250 that will not start. I have done everything I can think of get it going again...new plug(s), checked the wiring, new fuel, carb rebuild, etc. Spark is good, fuel flows to the carb, carb is rebuilt (set to stock specs), but yet it will not run for more than 10 seconds. I can kick the bike over 50+ times and it will not run, but the motor is new...less than 10 hours...and was put away in perfect running condition. Any thoughts?

[AL SS590 M6]

Almost has to be an electrical problem. I would suspect the coil is bad.

[Dave89IROC]

Almost has to be an electrical problem. I would suspect the coil is bad.
agreed, sounds like my buddies mini bike(honda 50)

[Timberwolf]

After it has run for 10 seconds, when you kick it the next time, is there GOOD spark? That would tell you if the coil was heating up and dying.
Also, pull the mag cover before you start it. As soon as it dies check to be sure nothing in there is moving from heat. The pickup, etc.
I agree it has to be electrical. heat = resistance

[IROCFST]

I would check compression. Did you rebuild the motor yourself? I never believe anybody unless they have receipts. I would also check the carb/floatbowl again , maybe the coil.:dunno: Maybe try spraying some gas or starting fluid in it to try to keep it running.

[HoogiesNgrinderz]

I would check compression. Did you rebuild the motor yourself? I never believe anybody unless they have receipts. I would also check the carb/floatbowl again , maybe the coil.:dunno: Maybe try spraying some gas or starting fluid in it to try to keep it running.

The motor was rebuilt by Olivers Garage located in Flushing, MI. I ride with the Olivers when I head up to Baldwin, so I know I didn't get hosed on the deal. I didn't have time to diagnose anything over the weekend, but come Friday I'm going to try all the suggestions. I need to pick up a Clymers, its so damn hard to find specs for older bikes :mad:

[Razmiblackz28]

Remember a gas engine only needs Compression, Fuel, Spark.
If anyone of those is gone, or out of time. No start. No run.

Fuel is the easiest one to substitute as an engine will run on WD40. I'm placing my bet its a fuel issue. The 10 second run is a rpm ramp up stall as it leans out and runs through the vapors in the crank/ports.
Don't get to far from the basics. Step back and diagnose it before you try to fix it.

Compression, Fuel, Spark.... chant it with me Compression, Fuel, Spark....
Don't assume or beleive, check it.