Question about Yamaha YZ 125 Motorcycles

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The motor sparks but its weak.

Hello i got a 1997 yz 80 2 stoke the motor has a new cdi and a band new piston but the motor will not spark if u kick it over slow u gotta kick it over fast to make it wanna spark alil bit is it my stator plate thats **** and if so were can i get one cheap

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Sounds like the source coil in the generator is failing , replace the item. it should not be too expensive from yamaha,or it could be the kill switch,you can disconnect this and see if your spark is improved

Posted on Sep 06, 2009


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Why02 yz 250 won't kick or pop start runs while pulling it but dies as it stop rolling?

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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Still wont stat new piston plug storor cdi coil no luck help

So you've tested a spare spark plug sitting outside grounded to cylinder and you defintely have good spark?
If it getting fuel? Is the enricher (choke) working?l

Apr 04, 2011 | 2003 Yamaha YZ 125

1 Answer

Weak spark--put on a new coil-didn't help--cdi box?

May be CDI, but check all your grounds first. Make sure you have a clean metal to metal connection of the coil to frame. Disconnect the leads going to the kill switch also. you may have a high resistance to ground short. Also, did you replace the lead coming out of the coil going into the spark plug? did you reuse the old lead?

Dec 04, 2010 | 2003 Yamaha YZ 250

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1980 xl125 has a very weak spark. Any way to test

Hello Definitely charge the battery to full and then test the spark. Joe

Apr 07, 2010 | 1997 Honda XLR 125 R

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My 125 yz has lost compression in the motor and will not kick over it has spark

if its a good spark it should start.try bump starting it,if no joy then possibly piston rings or other simalar.

Feb 15, 2010 | 2003 Yamaha YZ 125

1 Answer

Got given a old yz 80 changed piston and rings its fireing but wont start?

I'll start with the obvious.... have you tried removing the plug, putting a little gas in the cylinder, putting the plug in and wire back on and then kicking it over? If it starts, runs for a couple seconds and dies (burns off the gas you just put in there), it's a fuel or fuel delivery problem. Has the carb been cleaned, the needle and seat checked, the float height checked, air passages cleaned out, etc.? These carbs are famous for getting gummed up after sitting a while. (I have 4 dirtbikes and clean the carbs every spring before firing them up for the first time). Is the oil to fuel mix ratio correct? Too much oil will cause this as well. If it doesn't start with gas poured in the cylinder as mentioned above, check to see how strong of a spark you have and if the plug is gapped correctly. The spark should be bright blue. Hopefully you know how to check this, but if not, take the plug out, put the plug wire back on the plug and lay the electrode end of the plug (spark end) up against the cylinder head with the end of the plug touching metal and kick the kick starter over. You should see a bright blue spark. If it's a weak spark (not bright blue) it's an electrical problem such as a faulty coil. (WARNING: DO NOT HOLD THE PLUG IN PLACE WITH YOUR BARE HAND when kicking it over. You will get zapped good if the coil/spark are ok.) Try these troubleshooting tips and then let us know the result. We'll go from there.

Oct 29, 2009 | 2003 Yamaha YZ 125

1 Answer

Yamaha 1997 yz 80

try to change the magnetinc there are 4 or 5 or 6 coil or dynamo one of them is damage

Sep 22, 2009 | 2003 Yamaha YZ 125

1 Answer

2007 125 yz, has a miss before the power valve kicks in. short flat spot then , have keep the revs high to avoid it!!

There's no extra valve that kicks in to give the bike extra power. The term "power band" is simply referring to the RPM range of the motor that produces the most torque. Make sure the carb is clean and check the spark plug gap and fire. You need a hot blue,purplish fire not a weak white looking fire. If the plug itself is whitish in color you need to richen up the carb if it's black you'll need to lean it out. You should have a chocolate almond color. I'd bet the bike is getting too much air.

Aug 24, 2009 | 2003 Yamaha YZ 125

2 Answers

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

Jul 22, 2009 | 2003 Yamaha YZ 125

1 Answer

While riding my yz 125 it just died and won,t kick up again

  • If a hole in the piston then install new piston and rings. Next, clean the carbon off the head and install a new head gasket.
  • If cylinder wall is scared the piston has seized up. Pull the cylinder off and take it to the dealer. Have them bore the cylinder and return it along with a new oversize piston and rings.
  • While at the parts counter, get a new stock spark plug and a supply of Yamalube Two Stroke Motor Oil. You need to add 4 ounces per gallon when filling up. This will be a 32/1 gas to oil ratio. NEVER ride the bike without at least the needed 32/1 mix.
Please rate the solution as a "FixYa" if able. Thanks!

Mar 23, 2009 | 2003 Yamaha YZ 125

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