Question about 2003 Yamaha YZ 250
Put a new top end and i check if piston was in wrong but was not its geting fuel, and spark, air, compression and it backfires while trying to kick start exshaut pipe is not clog what could be?
Posted by Anonymous on
Hi, Anonymous you may have a faulty cdi or charging coil issue for this scenario you will need your service/owners manual if you can't find the first and best tool you ever bought for your Yamaha, despair not, for a mere $0 you can download another one. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
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YAMAHA YZ250 LC Owner Service Manual
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Posted on Jul 21, 2016
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Posted on Jan 02, 2017
2 stroke bike are very dependent on compression. and being a bike that is 12 years old my best educated guess is that the top end needs to be rebuilt. i usually have to have the top end done on my honda about every three years.
Posted on Jan 13, 2009
Posted on Mar 23, 2009
Hi, when you change your pipe to the FMF you reduced the back pressure and gave it more flow. That causes it to run a little "rich". Look at your spark plug and check the color of it, it should be a nice tan color. If its a dark brown then you need to "lean" out your bike. The easiest way to do that is by taking the slide out of the carb and taking out the main jet, the lock washer is set to the middle position for a stock set-up. Move it down 2 notches and then run it and see what your plug looks like. The black "goo" is the unburned oil from not running lean enough. Another trick to try is run a NGK-EV plug. it burns hotter so it will help with the oil problem (and make it a little more snappy also). And as an added bonus it will be easier to start.
Posted on Aug 23, 2009
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