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yz250 Pin found on magnetic drain bolt

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Hi,

Had my '07 YZ250 engine rebuilt about 5 hours ago by a shop which has since closed. Doing an oil change on the weekend I was surprised to see something attached to the end of the drain bolt (10mm socket for reference). 

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It's difficult to identify what pin this is, but I think it could be part of the YPVS Governor.

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I found another thread on this forum that starts with the discovery of a different pin but also ends up finding one that looks just like mine.

So before I start taking things apart, I have some questions:

  • What is the role of this pin?
  • Is it the pin in the attached diagram? If so, being part of the governor assembly, is it likely to be related to a weak top end? That would be my only complaint of the engine when i received it back. Riding this bike back to back with an '08 , theirs felt terrifying.
  • How could it have come loose? Installer error? Should I be concerned it will come loose again?
  • Is there anything I can do to prevent it coming loose again?
  • If it shows no signs of damage, is it safe to assume the internals (i.e. the parts that would require a case split to inspect) have not been damaged during its journey to the drain bolt? If not, what specifically should I check?

Lastly this post hopes to serve as a bit of a reference for anyone else who finds something similar.

Thanks guys :)

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If it is the governor pin it is 13.65 mm long and 3 mm diameter.

The pins role is to drive the weights in the governor.

It would affect top end performance because governor is essentially nonfunctional.

Pulling up and down on the linkage with Governor installed and the pin vertical can cause the pin to fall out. Some would argue that point but I know it to be true.

When reinstalled properly there is no concern of it coming apart again (unless you pull up and down on the linkage with it in the perfect orientation! Ha ha).

Just re-install it properly.

If that is truly the governor pin and it is not chewed up and still in good shape. That is most likely the only part that was floating around and it did not connect with anything fortunately. Pull the right side case reinstall the pin and ride

 

 

 

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PS… If that is the governor pin be very careful taking the right side case off. The governor will most likely come apart sending the four balls, bearing, washers etc. dropping who knows where. Refer to your parts diagram and make sure you have all the pieces.
The other pin most commonly reported floating around here on TT is the head alignment pins, I don't know their dimensions off the top of my head

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Guess there's a reason they are closed. maybe was their fault maybe not. Other pin is one Yamaha gives you for holding powervalve arm . But the gear must be broke or something don't see how could fall out unless something broke or come lose. Dig into it already :rolleyes:

Edited by Motox367

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But the gear must be broke or something don't see how could fall out unless something broke or come lose.

Motor at rest with pin in the vertical position. Pulling up on the linkage causes uneven pressure on the washers and bearing making them bind to the weight collar so the weight collar follows the linkage. Oil stiction and gravity (depending on the angle of the bike) causes the balls and weight retainer to follow the linkage abandoning the pin. Gravity and lubrication cause the pin to drop out. When linkage is released everything goes back in place without the pin. I have seen them fall out completely and part way out if the linkage is released catching the pin halfway out not allowing weight retainer to seat fully causing bike to run like crap in low-end.

The dowel Yamaha provides for holding the linkage is bigger at 28.75 mm long by 4 mm diameter.

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Thanks again Kinger317. You were correct, and installing it gave the bike back its topend :jawdrop:. Accidentally snapped a bolt off in the case during reassembly so getting to the track to test it out was a little delayed. All good now! Cheers all.

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Thanks again Kinger317. You were correct, and installing it gave the bike back its topend :jawdrop:. Accidentally snapped a bolt off in the case during reassembly so getting to the track to test it out was a little delayed. All good now! Cheers all.

Awesome, enjoy that power! And don't pull up on that linkage if you don't have to!
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On 7/11/2017 at 8:03 AM, Kinger317 said:

Motor at rest with pin in the vertical position. Pulling up on the linkage causes uneven pressure on the washers and bearing making them bind to the weight collar so the weight collar follows the linkage. Oil stiction and gravity (depending on the angle of the bike) causes the balls and weight retainer to follow the linkage abandoning the pin.

Kinger, I believe you and kinda understand what you mean about some binding which unloads the preload on the pin in the slot on the outside of the ball spinner.  However I'll have to check that out next time I have the right side cover off. I'm guessing you put the parts on without much oil or you pin wasn't deep in the slot. Every time I pulled my gov apart I needed substantial force to compress the spring to free that pin and manually moving the link arm is always loading that pin if you feel spring force.  I figure that somehow the pin needs to be completely unloaded and free of the slot.

11 hours ago, tkf said:

Accidentally snapped a bolt off in the case during reassembly

Which bolt?  If you do up any case bolt too tight I thought you'd crack the case alum or damage case threads or least kill a gasket before snapping a M6 bolt.

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Which bolt?  If you do up any case bolt too tight I thought you'd crack the case alum or damage case threads or least kill a gasket before snapping a M6 bolt.

When you pull up on the linkage it forces the spring into the gear, away from the pin.
Although I was trying, I was able to make a pin fall out in the bike.

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