Question about 2004 Yamaha YZ 125
Posted by Anonymous on
Hi, Anonymous there is no such thing as a weak spark even though dozens of riders will swear that's what they have and are dying to show you, the bottom line is either you have spark or don't have spark there is no in between.
You won't see a dirtbike spark really well, and people only look at it when they have a problem. It is designed to fire under extreme pressure (13:1 compression) and is very robust, but it is not a 1mm bright blue line jumping across a spark plug. It can be white and very hard to see. If you are confident you have weak or no spark prove it by holding the plug in your hand and stark kicking you will be in for a "SHOCKING" surprise!!!!!
60% of these bikes have a flooding issue and/or a fouled plug. 30% need valves adjusted and most of the remaining 10% are something simple in the electrics like a broken kill switch, bad earth on the battery or dead battery, wiring at the steering head damaged or blown fuse.
For more information about your question and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
Yamaha yz125 won spark
How to fix No Spark Problem on Motorcycles and Dirt Bikes
Yamaha YZ125T1 Owner Service Manual
OEM parts for Yamaha
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Posted on Apr 23, 2017
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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
Not much info Smitty but if that weak spark is constant (ie:pulsing ) i would guess that the trigger coil is ok.I'd make a check on your ignition coil earths then do a couple of continuity tests on your coil primary and secondary , orange terminal to ground,orange terminal to ht lead ,if they check out ok according to service manual specs then i'd run continuity test on the source coil.....Hope this is helpful in someway ...Smittycat.......from Flabbycat
Posted on Apr 19, 2009
SOURCE: what spark plug for yz 125?
I have a dennis kirk book, the correct spark plug is a --BR9ES--(NGK)
i always used SAE 10w-30 oil on all my dirtbikes,
no transmission fluid
for the chain you should move the back tire back until the chain is at a snug tension
Posted on Apr 24, 2009
You don't decode it. It is only a production run series number. Mororcycles are like cars in that respect. It is the frame number, AKA the "VIN number", is what carries all the information. Call a dealer with the frame number and he can tell you year, paint color, specific model and more. They may have a problem if the bike is too old. Yamaha changed to a newer code system a few years back.
Can I get a “very helpful” rating on this answer?
Posted on Aug 28, 2009
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