Question about 2003 Yamaha YZ 125

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Cracked crankcase 2003 Yamaha YZ 125

I have a yz 125 2003, it has a crack in the crank casing next to my kickstart, is it best to get it welded or the new casing? @

Posted by craig lindsay on


4 Related Answers


Paul W

  • 404 Answers

SOURCE: yz 250 wont kickstart

You obviously look after your machine and very sensible when laying up, however as you are probably aware 2 strokes rely heavily on compression, A. to produce excellent combustion and B. to draw fuel into the chamber. So when you try kick starting you can't get enough revolutions to draw the correct amount of fuel into the cylinder, where as you push start you constantly turn over the engine increasing compression slightly and bingo it fires.
Can you remember how when kick starting it before this problem the feel on resistance when kicking over? has it now become a lot easier? if so you possibly have worn or broken compression piston rings.
A compression test will reveal this, I hope this sorts your query?
Press the Blue button please for my FREE effort,
Thank You!
Paul 'W' U.K.

Posted on Feb 06, 2009


tim winter

  • 200 Answers

SOURCE: crack in my yz 125 2001 crank case

You know aluminum can be welded very successfully now, so best bet is to remove that case and take it in to a good welder..You can ry the quick fix (JB Weld) is what i recommend, but success is rare !....good luck to you my friend...Tim

Posted on May 10, 2009


Donald DCruz

  • 17130 Answers

SOURCE: i recently bought a yz 125 01, it was working fine

Yes , it seems that the case is broken which might require a welding and machining to fix. The engine cover has to be taken out for doing the job while the fault has occurred due to negligence. The kick start has a shaft with a bush which would have developed a play and thus the pressure was applied to the cover due to the play on the shaft,-- hence the oil leak .
Take estimate from a known mechanic / machine shop for the work before you start on it.

Posted on Feb 14, 2011

Michael Green

  • 3799 Answers

SOURCE: can a cracked 2008 ktm 85 sx be welded?

Yes it can be done, but Ally welding is not something for a novice. Find a local engineering company with a good reputation and they should be able to help.

Posted on Nov 11, 2012

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I recently bought a yz 125 01, it was working fine until my kickstart wasnt throwing back to the original position, i looked closely and i have cracked my crank case and it leaks oil how do i fix it and...

Is it definetely the crank case, if it is than it is a big job, if its just the outer cover you can start by removing the kick start, cover and anything else in he way and see how much damage there actually is!!! You also have the option of having it welded if parts are too expensive, service manual will give you full details

Feb 14, 2011 | 2003 Yamaha YZ 125

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Yz 125 2001 model. i went down to the garage and kickstarted the bike she fired up no problem then the engine cut out after a minute now the kickstart is real heavy too push down and will not start, any...

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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Crack in my yz 125 2001 crank case

some jb weld shouls work fine on it just get it good and clean no oil or paint on the crack. or find a tig and weld it.

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