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Cr125 ceased

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While I was riding yesterday my 03 cr125 started to bog out and die, the kick starter can't be kicked it's stuck, still new to 2 strokes I run 32-1 and just changed to transmission oil and spark plug. Any suggestions on what it is, I haven't been able to take it apart yet because of work

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A number of things could of happened. I'd start by pulling the exhaust and carb to take a look in the cylinder, then pull the clutch side outer case and the stator cover to see if there is anything obvious going on. Then most likely you'll have to split the cases and rebuild the bottom and top end. Is also look for a manual and all the tools required to rebuild the motor. Good luck

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A number of things could of happened. I'd start by pulling the exhaust and carb to take a look in the cylinder, then pull the clutch side outer case and the stator cover to see if there is anything obvious going on. Then most likely you'll have to split the cases and rebuild the bottom and top end. Is also look for a manual and all the tools required to rebuild the motor. Good luck

When I took it apart when I got it the top end looked new. But if it is the bottom end could it have ruined the top as well? And what am I looking for when I open the clutch cover?

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Take the cylinder off, start there. There's a number of things to make it seize. You'll know when the cylinder is off

I'm new to the 2 stroke world, if the top end looks good can I assume i need to rebuild the bottom or is there anything else it would be, I'm going to be taking it apart tomarrow

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I'm new to the 2 stroke world, if the top end looks good can I assume i need to rebuild the bottom or is there anything else it would be, I'm going to be taking it apart tomarrow

for the most part yes. I would also take the right side clutch cover off as well, that will allow you a better way to assess the damage. If you see anything suspicious you need an answer you can post pics

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for the most part yes. I would also take the right side clutch cover off as well, that will allow you a better way to assess the damage. If you see anything suspicious you need an answer you can post pics

Ok thanks for the help, I think I might take it to a shop to get it looked at if it's not the top end

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While I was riding yesterday my 03 cr125 started to bog out and die, the kick starter can't be kicked it's stuck, still new to 2 strokes I run 32-1 and just changed to transmission oil and spark plug. Any suggestions on what it is, I haven't been able to take it apart yet because of work

if it cant be kicked over after it has cooled down it's the big end bearing that failed. Do you know when was that last time it was replaced (running hours) ? Those Hondas are reliable but it's still a racing engine and those will fail.

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if it cant be kicked over after it has cooled down it's the big end bearing that failed. Do you know when was that last time it was replaced (running hours) ? Those Hondas are reliable but it's still a racing engine and those will fail.

No I don't I bought it from craigslist and the guy said he put a new top end. How costly and hard is it to fix the big end bearing?

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It's not that it expensive of course depending from where you are. If you're from USA it's not too bad. Easiest way is to buy a new crank. Other way is to buy for example Prox con.rod kit and take your crank into a bike shop and let them replace it. It's a bit cheaper that way. You'll also need new main bearings and a complete engine gasket set. If you're unlucky bits and pieces from the big end might have come up and brake your piston and cylinder. That usually doesn't happen but it's possible. I'd also replace the small end bearing even if the piston is ok. Of course when I say it's not too expensive, I mean that you'll do the work yourself. You can get a new crank from E-bay around 200 USD and the con.rod kit is about 100 USD. Gaskets around 60 ,-  small end bearing around 15 ,-. Main bearing set probably 50. -

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It's not that it expensive of course depending from where you are. If you're from USA it's not too bad. Easiest way is to buy a new crank. Other way is to buy for example Prox con.rod kit and take your crank into a bike shop and let them replace it. It's a bit cheaper that way. You'll also need new main bearings and a complete engine gasket set. If you're unlucky bits and pieces from the big end might have come up and brake your piston and cylinder. That usually doesn't happen but it's possible. I'd also replace the small end bearing even if the piston is ok. Of course when I say it's not too expensive, I mean that you'll do the work yourself. You can get a new crank from E-bay around 200 USD and the con.rod kit is about 100 USD. Gaskets around 60 ,- small end bearing around 15 ,-. Main bearing set probably 50. -

http://www.motosport.com/dirtbike/WISECO-COMPLETE-CRANK-KIT

Is this what I would need?

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That is a complete bottom end re-built kit. Here's the thing, I'm not about to "bad mouth" about this Wiseco kit. I'm only telling you that, I installed one of these in our Honda and it blew the big end in under 50 h ! Now I know my sons had changed the 2 stroke oil at the same time so maybe it wasn't good enough oil they were using at that point. Since then I told them to go back using Motorex Cross power fully synthetic. It's quite expensive but it works. Having said that, I have one of these kits on the shelf waiting to go in. So I guess I haven't lost my faith completely with this kit  :rolleyes:  . If I remember right you still have to buy some seals like counter shaft seal (I'd buy the bushing also).

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No, get the wiseco top end (for your 03) and then hot rods or OEM bottom end (for an 05cr125) the 05+ crankshafts are less prone to failure.

Also word on the street is wiseco cranks are junk. Idk I've never used one. Best to not risk it and use an alternative

Edited by zotis777

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I'd stay away from Wiseco pistons since it's a two stroke and they don't like forged pistons. Go with Vertex piston very good cast piston. We've been using their replica pistons and they've been relly good. Now I know  some people think differently but I gotta say (I think I just put my head in the hornets nest with this), even during my road race career I never used firged pistons on a 2 stroke. 4 stroke is a different thing but that's just my 2 cents (and Vertex')

http://www.na.vertexpistons.com/

 

What’s better and why:

Vertex Two-stroke Pistons
Because of a cast piston’s ability to contain higher silicon
content compared to forged pistons, and because twostrokes
have lower cylinder pressures when compared to
four-strokes, cast pistons are ideal for two-stroke engines.
Vertex pistons are gravity cast from an aluminum alloy with
18% silicon content. Silicon is important because:
• It decreases thermal expansion, which changes the
geometry after the piston reaches operating temperature.
With low thermal expansion characteristics, Vertex
pistons can be run at tighter tolerances compared
with forged pistons. This creates better power and
performance, also making them less susceptible to
rattling or breaking.
• Silicon gives the pistons better wear characteristics and
prolongs piston life by decreasing wear on the piston.

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I have one of those Wiseco kits on the shelf since I bought two last time (we have two bikes). But like said, our experience with the first one wasn't good. If the next one goes under 150h that's it for me. Before I used to buy Prox con.rod kit and everything else separately. It was more expensive but it worked really good. 

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