2004 Yamaha YZ 125 Logo

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Posted on Jan 23, 2011
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Got a 2002 yz 125 seems like power band doesnt kick like it lost the "bing bing its firing has a new plug new ring good compression power valves in jug are clean and carb is clean not too sure on the section of power valve in crankcase though

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5 Related Answers

Anonymous

  • 2336 Answers
  • Posted on Nov 10, 2008

SOURCE: Loss of compression

I dont have a 4 stroke, but lack of compression on any engine is bad news. You need to take the engine apart, the piston ring is shot or maybe you have valve issues. I love the Turtle Posse!

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Ernest Stalker

  • 53 Answers
  • Posted on Jan 13, 2009

SOURCE: 1997 yz 125 wont start, please help

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.

tombones

  • 3567 Answers
  • Posted on Mar 23, 2009

SOURCE: 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!

Anonymous

  • 1 Answer
  • Posted on May 14, 2009

SOURCE: Loss of compression with dtr 125, kick start

It could be a number of things,difficult to say on bike engines,it could be the rings have collapsed,piston damaged or gudgeon pin broken.It will be best if you open engine and check internal parts and take it from there,it will work out cheaper

tombones

  • 3567 Answers
  • Posted on Jul 06, 2009

SOURCE: yamaha yz 125 1994

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Related Questions:

0helpful
1answer

Yz 125
If the plugs are fouling from excessive oil then it may be that the oil ring is broken. That will be scoring the bore and accounting for the low compression pressure. To do compression checks the motor has to be hot and the throttle wide open. Check for blocked filter before testing. IN the short term run a hot plug . ( where the porcelain insulator is very long in the plug) as this will help it burning off the oil .
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Apr 28, 2013 • Motorcycles
3helpful
1answer

My yz 125 made a loud popping noise when i tried to kick it up now it wont start any suggestions
They can do this from time to time. What can happen is the expansion chamber gets pumped with fuel vapor and then can be ignited, causing a large backfire. I hate to attempt to answer your question with a question, but how old is the piston and ring? A ring won't last very long in a 125. For racing, it's changed every race. For joy riding 15-20 hours of run time and it's time for a ring at least. Weak compression can make it impossible to start. If you have perfect compression the cause for the non-start could be something as simple as a burned up or fouled spark plug.

Start by re-ringing the motor (you can do this for about $25 inside of 2 hours time). Clean the carb out, clean the air filter, fill the tank with fresh fuel and replace the spark plug (NGK B9ES - from Autozone for $1.89). If the bottom end of the engine is good, the above steps should get it fired up - providing your ignition system is good, and based on the apparent backfire, I would say you have spark.

Scott
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May 17, 2011 • 2003 Yamaha YZ 125
0helpful
1answer

I have a 2000 yz 125. Melted a hole in the piston but didnt score cylinder. Replaced top end. Wont start. Has good fire. Crank case oil was a little grey. New plug,fluids,fuel.
I would be checking compression it may not be visible score on cylinder but it does not take much to loose compression on small bore motor with one piston ring and 11 years old
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Mar 03, 2011 • 2003 Yamaha YZ 125
0helpful
1answer

Yz 125 2001. starting ploblem after top end rebuild
Kinda sounds like your needle valve is sticking in your carb and it is giving it to much fuel
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Jun 03, 2010 • 2003 Yamaha YZ 125
0helpful
1answer

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.
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Feb 15, 2010 • 2003 Yamaha YZ 125
1helpful
2answers

My tm 125 suddenly lost all its power and isnt reaving out proplry. is my engine gone?
piston rings by the sound off it or spark plug lose 1 st get a compression tester take the plug out and screw the compression tester in the spak plug hole and kick the bike over and see what psi it reaches get back to me 5035507.jpg
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Sep 27, 2009 • 2002 TM Racing E 125
1helpful
1answer

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.
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Aug 24, 2009 • 2003 Yamaha YZ 125
2helpful
1answer

Whilst riding at long periods at high speed my bike just shut down and didnt seem to have compression once i went to kick start it again.yz 125
It sounds like you cooked her. If you are jetted lean, and run it wide open for a long period of time, it melts the ring to the piston.
Do a compression test, remove spark plug, thread in gauge, and hold throttle wide open and kick untill the guage stops climbing (Around ten or so) Less than 100 psi is bad.
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Jul 13, 2009 • Yamaha YZ 125 Motorcycles
0helpful
1answer

Yz 250 1992 wont kick start
check your compression I had a 94 yz that done that when i checked the compression it was really low so I put new rings on the piston and that's all it took to bring her back to life
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Feb 03, 2009 • 2000 Yamaha DT 125 R
1helpful
5answers

1997 yz 125 wont start, please help
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.
Read full answer
Jan 12, 2009 • 2003 Yamaha YZ 125
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