1989 yz 250 no spark

SOURCE: how to set a power valve on a yz 250 1989 and how

Google " service manuals yamaha "
or go to www.repairmanuals.com
or try your local library. Often guys will donate manuals to the library.

You might find a free pdf service manual on this site, they have a ton of them.
http://www.carlsalter.com/motorcycle-manuals.asp

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SOURCE: yz125 no spark

G'day i am a . YZ 125 j ...lets see now! You could perform these tests yourself.Check your plug CAP,if in doubt replace it with a new one. Take the below ohm figures and see if they match up. Pulse coil: white/blue and white/red= 310 ohms. low speed coil: Green/white and Black/red= 900 ohms. high speed coil: Green/blue and black= 55 ohms. hope this has helped in some way to helping you solve your problem.If it has please leave feed back.Ride hard , see ya,Tabbycat

SOURCE: My yamaha yz 250 ruins spark plugs in about 5 min

first determine condition of cylinder by a compression test. if compression is ok, you are either running too rich of a fuel/oil mixture, slow running or idling too much, "2 strokes are not meant to idle very much without "cleaning out" or revving the engine to rid itself of carbon buildup from excessive oil burn. you may also want to try running a hotter plug. go up one heat range ,"down in number" at a time. if your not familiar with doing this, ou could overheat your engine. so be careful!

SOURCE: backfire

Your plug may be firing in a fouled area. When I have a problem like this, I 1.change the plug. 2. Take the carb and have it cleaned in a sonic bath and my honda dealer(They are the only one with this cleaner in my area) for about $25. 3. Check to insure that the fuel mixture screw is set correctly(about 2.5 turns), and 4.clean the air filter or replace it.

SOURCE: My Rm 250 wont spark

REplace coil MOPAR KENNY