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Yz125 help

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Ok I had bought a new rebuilt yz125 got it running then blew the bearing in the crankshaft. I bought the new parts to replace had a buddy install the parts then put motor back in bike and I go to kick start it and nothing. No compression just spins the gears inside. I put it in gear and kick it it will move the bike forward. But when I put in neutral it won't move the piston. Need help.

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Sounds like the output gear on the crankshaft isnt meshing with the clutch basket gear... or possible broken teeth maybe. Pull the plug and confirm its not rotating the crank assembly first 

Failing that pull the side cover off and inspect gear mesh for any damage etc 

Edited by Wilksy

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Ok I'll check tomorrow. All the gears were good I made sure what wasn't good was replaced.

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Did he put the piston/rings back in the cylinder?

 

 

Yes

I can put it in gear and kick it and it almost sounds like it wants to turn over

 

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Just now, sooners said:

 

 


Yes

I have never experienced a bike that had zero compression when kick starting.

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Net time take it to someone that knows what their doing maybe :thumbsup:



He's put them together all his life and races them not sure what he did wrong

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8 minutes ago, sooners said:

 

 


He's put them together all his life and races them not sure what he did wrong

 

 

Take it back to him then he should be able to fix it. 

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1 minute ago, sooners said:

He's my neighbor and he's trying

Good to hear :thumbsup:

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Update us on this mystery when it's resolved. Perhaps he forgot to tighten the crank primary gear or piston rings..

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19 hours ago, Narciss said:

piston rings

Bah, they only add more weight anyways!

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25 minutes ago, sooners said:

Well I found the problem a gear was left out

Wow lol kickstart idler gear I bet?

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14 hours ago, Motox367 said:

Wow lol kickstart idler gear I bet?

More like the primary crank gear, since the bike moves when kickstarter turns.. also the bike would push start when in gear if that was the case.

 

Well, seems it was a harmless mistake. Better than not tightening it, I guess.

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IMG_0894.JPG

IMG_0894.JPG

More like the primary crank gear, since the bike moves when kickstarter turns.. also the bike would push start when in gear if that was the case.
 
Well, seems it was a harmless mistake. Better than not tightening it, I guess.

IMG_0894.JPG

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Small gear that wasn't even in there so I took the casing off put back on and the bolt to hold it on and put everything back and now the bike kicks over like normal. Will be putting in all fluids and testing today or tomorrow. Will update whether it runs or not

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It should start. How did you tighten the gear, how did you hold it in place?

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It should start. How did you tighten the gear, how did you hold it in place?



There was a bolt that went on after and I put that on now it stays and don't move. He never put the gear in or bolt

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