Motorcycle Questions? Ask a Mechanic.
Hi and thank you for your question.
1.) Exactly what was replaced in the rebuild and was the work performed by a trained professional?
2.) Why did it need a re-build?
3.) Have you done any diagnostics like checking for spark, compression or if fuel is getting to the spark plug?
If not, that is an excellent place to start.
Please do a compression test on your engine and get back with results. Please be specific in replies, such as hard numbers. Something is obviously wrong since it isn't starting, so something is being overlooked. An engine requires sufficient compression, fuel at the correct ratio and spark at the correct time. We just need to figure out which one is missing.
What year is your bike? Is it a CRF250F or CRF250R, M what?