20 Most Recent 2005 Yamaha yZ 250 F Questions & Answers

Sorry to hear your bike stopped - There are way to many possibilities for this but the best advice i can give would be two things, (1) get a leak down test done (at shop if you don't have tools to do this) It will give accurate answers to if compression is low or valves are leaking etc (2) Check to see if you have spark to spark plug by kick starting bike with the spark plug connected and laying on the head of motor ( should be a nice clean blue spark)
if you have no spark then almost guarantied you need a new stator installed but this can be easily tested with a multimeter to confirm before you buy new stator let me know if you want more detail on tests etc
good luck mate regards Jamie

Hey Anon, Proper and correct jetting is something that can only be achieved in person by a REAL MECHANIC that KNOWS how to "read" a spark plug,,,With the mods you mentioned.. you need to know the stock jet sizes..a close guess would be reduce the main jet by two or three steps and lower the needle one clip position... oil mix should be at least 32:1....or better yet 28:1.. KEEP the oil mixture and jet the carb for performance....( I see TOO MANY IDIOTS that instead of jetting a carb correctly just reduce the oil ..some as low as 50:1(INSANE) just to keep from fouling plugs.).. then WONDER why their engine doesn't last long... hahaha???? YOU > BE SMART!!

Once I heard the story from my client, I established out to test the concept, beginning with those suffering the most. Your Fun Quirky Telephone AmanStino

Beings the master cylinder was used, it might need to be rebuilt. http://www.bikebandit.com/houseofmotorcycles/2005-yamaha-yz250f-yz250ft-rear-master-cylinder/o/m145329sch523035 Item #2

Valve adjustment is need

bad mixture, whats air filter like is it restricting airflow