08 YZ 125 Timing

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6/24/2018 10:33 AM

Sow while troubleshooting a bogging condition I decided to check the crank seals (will just change since I'm in there). I loosely decided to check the timing. Following the manual and using a dial indicator it just doesn't align. Not close.. It states to find TDC. Easy enough with the dial indicator. Form there is says to turn clockwise the appropriate amount. (.019 inches). Dial indicator is .001 each . When I do this the mark on flywheel is at least an inch form the timing mark What am I missing? There isn't all that much adjustment.

Thank You

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6/24/2018 12:19 PM

Are you spinning the crank the right way? You might be after TDC, not before.

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6/24/2018 12:42 PM

Can you post up a copy of that part of the manual? Something does not sound right to me.

Paw Paw

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6/24/2018 2:31 PM

I agree, try spinning opposite direction. Manual says clockwise but diagram opposite.

Photo

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6/24/2018 3:09 PM

chillrich wrote:

I agree, try spinning opposite direction. Manual says clockwise but diagram opposite.

Photo

Thanks for posting that. So I found TDC spinning it counter clockwise. Then clockwise 19 increments. Still off about 1 1/2 inches from the mark. Doesn't make sense.

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6/24/2018 3:20 PM

Are you sure your crankshaft key is good and not broken?

Paw Paw

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6/24/2018 3:32 PM
Edited Date/Time: 6/24/2018 3:33 PM

Paw,

I have the flywheel off,Eyeballing the key way and groove in flywheel to be sure. I just put it at TDC. The flywheel mark is 1 1/2 inches to the left of stator mark. Took a picture but not sure how to upload here.

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6/24/2018 3:37 PM

MXRICH wrote:

Paw,

I have the flywheel off,Eyeballing the key way and groove in flywheel to be sure. I just put it at TDC. The flywheel mark is 1 1/2 inches to the left of stator mark. Took a picture but not sure how to upload here.

Photo
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6/24/2018 6:39 PM

Is it an OEM crank? There have been known cases of aftermarket cranks having the key groove clocked with some significant error.

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Powerband in every gear !

6/24/2018 7:33 PM

And when you rotate it clockwise to the correct timing, where is the flywheel then? Put the key in to be sure!
That raised part of the flywheel is the trigger tab to trigger the pick up coil so you get spark and it should be back in the correct place when you do the clockwise move as per the manual.

Paw Paw

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6/25/2018 1:06 AM

It is an OEM crank. The key is indeed in. Just that flywheel isn't torqued in to spec so I can slip it off checking to make sure flywheel and crank have not mis-aligned. Where should "trigger" be when at correct timing? Just beginning to trigger or mid-point of the pickup coil? Photo

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6/25/2018 4:49 AM

It should be at the end of the trigger as it is a magnetic pulse and when it breaks the field it will send the impulse to create the firing of the plug.

Paw Paw

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6/25/2018 5:15 AM

Paw,

It does appear to you then that something is amiss with the manual? I will adjust the stator accordingly by the "trigger".

Unfortunately I don't have access to another YZ to reference.

Thank You

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6/25/2018 6:31 AM

Out side of the one direction issue in the manual it seems to be otherwise correct. Your last photo seems to also show to be correct, from what I can see.
Remember that the flywheel rotates counterclockwise and thus in the position in the last photo would seem to show that the trigger tab on the flywheel is just about to clear the pulse coil which then would create the pulse to create the fire to the plug.

Paw Paw

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6/25/2018 7:11 AM

Paw Paw,

I agree and that is how I will set it. Unfortunately the manual shows the mark on the flywheel should align with the mark on the stator and that misses by quite a bit.

If you don't mind another quick question, while OHMing the coil. On the primary coil resistance. Manual says .24 - .36 ohms. When I use my Fluke DVM, it reads .4-.5 ohms. Is my coil out of spec OR is the DVM not accurate enough to pickup that low resistance?

THANK YOU AGAIN.

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6/25/2018 8:31 AM

If in fact you are reading the primary side, that reading should be ok. If it were lower than spec's then the coil would break down under load or heat and you would loose spark. If on the other had you are reading the secondary side, I would look for some dirt or bad connection at the plug cap and or wire. If that reading gets above spec's it will hold back the spark transfer.
I can't see the mark on the stator as it relates to the flywheel so I am not sure what is going on there.

Paw Paw

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6/25/2018 8:17 PM

Does this help? This should be how it looks at 0.019" BTDC Photo

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6/26/2018 5:25 AM

Thank you...

Paw Paw

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6/26/2018 7:51 AM

Chillrich, Paw Paw,

Want to THANK YOU both for your help here. The explanations and diagrams were a great help. I'll let you know when it's all back together how it turns out.

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