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KX125 crank question

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Hey guys, new to the site and looking for a little help. The motor in my 01 KX125 seized on me and after opening it up I found that the big end connecting rod bearing was shot. Upon further inspection and teardown, it looks like there was a LOT of heat in the bottom end. I'm having trouble finding a new crank assembly for an 01, which is apparently an odd in between year before the update in 03, but I do have a new connecting rod as well as crank bearings/seals. my question is, after looking at the picture below, is this crank salvageable? If so, is it worth my time to take is apart and try to get it back together perfectly, or should I just send it out? I'm a mechanic by trade, but this is my first bottom end on a bike, and I keep hearing horror stories about how much of a PITA the crank can be to get right. I have a press, calipers, etc so tools aren't the question really, just wondering if its as bad as people tell me. Thanks for any help!

-Patrick

 

 

78EF5D6D-A1F9-46DE-85ED-4A75AFC3E63D_zps

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Hey guys, new to the site and looking for a little help. The motor in my 01 KX125 seized on me and after opening it up I found that the big end connecting rod bearing was shot. Upon further inspection and teardown, it looks like there was a LOT of heat in the bottom end. I'm having trouble finding a new crank assembly for an 01, which is apparently an odd in between year before the update in 03, but I do have a new connecting rod as well as crank bearings/seals. my question is, after looking at the picture below, is this crank salvageable? If so, is it worth my time to take is apart and try to get it back together perfectly, or should I just send it out? I'm a mechanic by trade, but this is my first bottom end on a bike, and I keep hearing horror stories about how much of a PITA the crank can be to get right. I have a press, calipers, etc so tools aren't the question really, just wondering if its as bad as people tell me. Thanks for any help!

-Patrick

 

 

 

You'll have to check the run-out, side clearance, etc...to know if it's "good" or not.  I just rebuilt my son's kx-125 (1994) and there is no crank assembly available for that year either.  Not OEM, Wiseco, or Hot Rods...  My ONLY option was to send it out.  I bought the new parts, then had it rebuilt....the labor and shipping was $125.  A complete bottom end kit is generally the most feasible option, but not always an available option.   I would not suggest trying to do the crank yourself...

 

A little heat bluing on the crank is no biggy.  My crank was original, 20 years old and the rebuilder told me it was still well within spec, but I couldn't bring myself to split the cases only to replace SOME and not all of the parts...

 

Good luck ;)

Edited by Fattonz

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That crank was rebuilt once before.Some rebuilders will heat the crank with a torch for easier pin installation, but is not a preferred method, as the crank could fail prematuraly

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This crank should probably should not be rebuilt. Pin holes are induction hardened so that the crank pin does not gull the crank pin hole during assembly. Loosening the press fit.

This crank has overheated (this is not induction blueing) from bearing failure and more than likely ruined the pin bore hardness.

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However, if you welded the crank you might be ok. I personally don't like welded cranks because the welder needs to be very qualified.

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If I pulled that out of my own bike, I would have one term: paperweight

 

No way I would run it.

 

Hopefully you can find a new or used OEM to replace/rebuild.

 

Weigh the cost vs. chance on rebuilding a crank yourself.  Crank rebuilders such as Crankworks, Ken O'connor and others are quite experienced at something that is not easy to get right and very tough to take back apart and recheck.

 

Good luck and congratulations on getting the bike going again.

 

How did it get damaged?

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I 110% agree with Ken Oconner cranks. That guy builds some badass cranks.

 

If you choose to do it yourself, you'll need  a good set of v blocks, min. of 20 ton press, feeler gauges, dial indicator on a stand and a good brass hammer. Takes me about 30-45 min.

 

Note** I did visit the local metal and welding supply to scrounge some specific pieces of barstock.

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I 110% agree with Ken Oconner cranks. That guy builds some badass cranks.

 

If you choose to do it yourself, you'll need  a good set of v blocks, min. of 20 ton press, feeler gauges, dial indicator on a stand and a good brass hammer. Takes me about 30-45 min.

 

Note** I did visit the local metal and welding supply to scrounge some specific pieces of barstock.

 

Were you looking for bar stock for placing between the webs to press the crank apart?  When I took my son's kx-125 (1994)crank to our local guy he wasn't able to press it apart and eventually had to outsource.  Every piece of metal he tried just bent under the force.  He searched everywhere to find the actual jig to no avail.  He was pretty frustrated because up until a couple of years ago I guess he was building several cranks a week.  Apparently it's becoming a lost art these days, as most people opt for a drop in kit...  

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WHAT AN IDIOT I AM!!!!

Chokey, thanks for providing the oomph.

 

www.ronayers.com is where I buy a lot of OEM and aftermarket parts.

 

13031 13031-1465 CRANKSHAFT-COMP 1     $183.35

 

 

As shown on the home page, shipfree13 is a coupon you can use for free shipping.  Unless someone can remind my aging self of something better, that seems like the way to go.

 

 

EDIT:  1999 superseeds to the 2000 and 2001 part number.

Edited by KDXGarage

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Thanks for the help guys, I'm going to order the new crank tomorrow. As soon as the bike is back together I'll let you know what happens. Thanks again!

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So after chasing some parts and having life get in the way, I FINALLY got the bike back together and ready to start tonight. It's starts and runs great, with one problem, I can't get the trans to shift. When I split the cases the guts of the trans fell out, but I used the factory manual during assembly and paid very close attention to what I did and where everything went. It's not dog locked, I can spin the input shaft by hand, and the output spins, but I can't get it to shift. I pulled the clutch/basket back out and tinkered with the cog on the end of the drum, but I still couldn't get anything to budge. Any ideas? I really really don't want to split the cases again.

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