2006 YZ 125 crank identification

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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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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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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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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 kind of.

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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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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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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 kind of.

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!





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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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!