2004 Yamaha YZ 125 Logo

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Posted on May 19, 2010

Im losing spark after my yz 125 engine warms up, why?

5 Related Answers

FoRdMaStEr

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.

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Anonymous

  • 56 Answers
  • Posted on Apr 19, 2009

SOURCE: 1999 yz 125 weak spark won't start

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

Anonymous

  • 44 Answers
  • Posted on Apr 24, 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

tombones

  • 3567 Answers
  • Posted on Aug 28, 2009

SOURCE: how do i decode yamaha yz 125 engin id number

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?

Anonymous

  • 170 Answers
  • Posted on Aug 31, 2009

SOURCE: yz 125 water pump seal

GET A SMALL SCREW DIVER IN BETWEEN THE SHAFT AND SEAL PRY IT OUT WITH OUT DAMAGING THE SHAFT THEN USE A SOCKET FROM A TOOL KIT THAT FITS PERFECTLY AROUND THE EDGE OF THE NEW SEAL TO HAMMER IT BACK IN

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No spark on my yz 125 2006 model

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Sounds like the piston seized.
Pull the spark plug and hand crank the engine if the piston moves up and down with little effort your ok but if you have a lot of resistance top end rebuild needed.

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since you are rebuilding this engine ... you should hone the cylinder for the best fit for the new rings.
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My yamaha yz 125

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Sparks from my exhaust ??? Yamaha yz 125

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2003 yamaha yz 125 won't start

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125 wont start

hello
that does sound very similar to a loss of comrpession. usually what happens when you lose compression, and you load the cylinder up with fuel the plug starts to ignite it a little and does not actually combust. i would still definately reccomend sticking a comrpession gauge on it to make sure though.
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Engine oil it top ov head on 2 stroke yz 80 im thnkin gaskets

Wash the bike then tighten down the cylinder head bolts.
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