Forum Main Tech Help/Race Shop 2006 YZ 125 crank identification

2006 YZ 125 crank identification

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PremixKid

Vital MX member PremixKid 55178 PremixKid https://p.vitalmx.com/photos/users/55178/avatar/c50_5759_1506485305.jpg?1506484845 https://www.vitalmx.com/community/PremixKid,55178/all 12/10/16 https://www.vitalmx.com/community/PremixKid,55178/setup 1 73 30

Posts: 74

Joined: 12/10/2016

Location: St. George, UT USA

8/4/2017 8:51 PM

Hello guys,

My yz started to run really hot last time I rode it so I ran a leak down test on it and it failed, psi dropped from 6 to 4 is about 1 minute. So we are planing on replacing both crank seals and also a new piston.

We we pulled the cylinder off we noticed it was ported and also had a oversize piston in it. But the crank has these weird grooves machined into it.
Has anyone ever seen this before? I googled stock cranks and all the photos showed a smooth crank.

Any ideas on these grooves? Also when I got the bike the jetting was very rich, we bought all stock jets and got it close, but not perfect. Anyone has any starting points for 144 jetting? I live at 5000 feet.

Thanks


PhotoPhoto

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paddyB745

Vital MX member paddyB745 25994 paddyB745 https://p.vitalmx.com/photos/users/25994/avatar/c50_IMG_0024_1479710433.jpg?1479709543 https://www.vitalmx.com/community/paddyB745,25994/all 02/09/11 26 123 5

Posts: 149

Joined: 2/9/2011

Location: novato, CA USA

8/4/2017 9:10 PM

Looks like someone's attempt at a "turbo" crank. Never seen it done like that before though.

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rmoto003

Vital MX member rmoto003 56473 rmoto003 /images/default/avatar/c50.png https://www.vitalmx.com/community/rmoto003,56473/all 02/26/17 14 902 6

Posts: 916

Joined: 2/26/2017

Location: Gulf Shores, AL USA

8/4/2017 9:51 PM

Ah see you got the inverse reduction amplification crank modulator. Helps mix the gas and the oil together, like a blender kind of.

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slipdog

Vital MX member slipdog 16124 slipdog https://p.vitalmx.com/photos/users/16124/avatar/c50_Screenshot_2021_03_23_at_6.44.12_PM_Edited_1616550523.jpg?1616550389 https://www.vitalmx.com/community/slipdog,16124/all 07/25/09 16 1 48 9868 119

Posts: 9918

Joined: 7/25/2009

Location: Nor Cal, CA USA

8/5/2017 8:10 AM

rmoto003 wrote:

Ah see you got the inverse reduction amplification crank modulator. Helps mix the gas and the oil together, like a blender ...more

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CrGuy2T

Vital MX member CrGuy2T 46441 CrGuy2T https://p.vitalmx.com/photos/users/46441/avatar/c50_image_1426177274.jpg?1426176494 https://www.vitalmx.com/community/CrGuy2T,46441/all 03/11/15 26 388 3178 3

Posts: 3566

Joined: 3/11/2015

Location: Santa Fe, TX USA

8/5/2017 1:25 PM
Edited Date/Time: 8/5/2017 1:27 PM

that's basically a helical gear cut. I'm not to sure of the exact purpose but, my guess it's to force the excel premix in to the main bearings. It will also lighten the crank significantly along with an even machine probably pretty easy to balance.

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PremixKid

Vital MX member PremixKid 55178 PremixKid https://p.vitalmx.com/photos/users/55178/avatar/c50_5759_1506485305.jpg?1506484845 https://www.vitalmx.com/community/PremixKid,55178/all 12/10/16 https://www.vitalmx.com/community/PremixKid,55178/setup 1 73 30

Posts: 74

Joined: 12/10/2016

Location: St. George, UT USA

8/5/2017 8:50 PM

Thanks guys, getting the cylinder replated and ordering seals soon. Still would like to know the story behind this crank.

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kzizok

Vital MX member kzizok 23101 kzizok https://p.vitalmx.com/photos/users/23101/avatar/c50_695F74E8_8FD9_4245_8A79_D151E0912ACD_1523480876.jpg?1523480527 https://www.vitalmx.com/community/kzizok,23101/all 10/19/10 5 150 8149 10

Posts: 8299

Joined: 10/19/2010

Location: AS, USA

8/5/2017 9:11 PM

rmoto003 wrote:

Ah see you got the inverse reduction amplification crank modulator. Helps mix the gas and the oil together, like a blender ...more

slipdog wrote:

That never gets old!laughing laughing Remember this one?:
https://m.youtube.com/watch?devin-davisdQw4w9WgXcQvin

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much ty. How to spot a paid forum poster/artificial forum traffic producer (see list of actions/phrases below):

Copius pattern amounts of phrases like “Anyone have”..., “Anybody know?”.... and their variations.

Thoughts?
Any help is appreciated!
Thanks in advance!





slipdog

Vital MX member slipdog 16124 slipdog https://p.vitalmx.com/photos/users/16124/avatar/c50_Screenshot_2021_03_23_at_6.44.12_PM_Edited_1616550523.jpg?1616550389 https://www.vitalmx.com/community/slipdog,16124/all 07/25/09 16 1 48 9868 119

Posts: 9918

Joined: 7/25/2009

Location: Nor Cal, CA USA

8/6/2017 7:06 AM

kzizok wrote:

That never gets old!laughing laughing Remember this one?:
https://m.youtube.com/watch?devin-davisdQw4w9WgXcQvin

Photo

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kzizok

Vital MX member kzizok 23101 kzizok https://p.vitalmx.com/photos/users/23101/avatar/c50_695F74E8_8FD9_4245_8A79_D151E0912ACD_1523480876.jpg?1523480527 https://www.vitalmx.com/community/kzizok,23101/all 10/19/10 5 150 8149 10

Posts: 8299

Joined: 10/19/2010

Location: AS, USA

8/6/2017 4:37 PM

Slip,

You are one funny motherscratcher! I literally LOL'd!

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much ty. How to spot a paid forum poster/artificial forum traffic producer (see list of actions/phrases below):

Copius pattern amounts of phrases like “Anyone have”..., “Anybody know?”.... and their variations.

Thoughts?
Any help is appreciated!
Thanks in advance!





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