Help: Can't remove 2018 YZ-250 Cylinder Head.

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9/22/2018 11:58 AM

Whelp, this one's got me scratching my head. I tried removing the cylinder head today from my sons 18' YZ-250X and ran into a little problem. Because of the lack of clearance between the head stay and the frame, I can't lift the head high enough to clear the rear cylinder studs and pull the head out. What am I missing here? This is our first YZ, but I'm finding it difficult to believe this is the way Yamaha designed it? Thinking maybe the factory didn't sink the studs far enough into the cylinder.

What do you guy's think? Any of you YZ-250 guru's familiar with this problem? Looks like the easiest solution is to tighten the rear studs enough to give me the clearance. I could also try removing some of the aluminum from the frame with a dremel, but prefer not to do that if possible.

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9/22/2018 12:06 PM

To me based on seeing threads then unthreaded then threads again it makes me think you’re right and theyre just not tight enough

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9/22/2018 12:15 PM

Kx125rider wrote:

To me based on seeing threads then unthreaded then threads again it makes me think you’re right and theyre just not tight ...more

Ya agreed, I remember there being a little clearance on my old yz 250. Is the cylinder still bolted down as well? If not, tighten that back up a bit and try to turn those studs in as mentioned above.

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9/22/2018 12:29 PM
Edited Date/Time: 9/22/2018 12:30 PM

Just pulled the two lower engine mounts out and drop the engine down it'll come right out

Just read the other two comments you definitely backed out the studs

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9/22/2018 12:45 PM

double nut the stud (tighten two nuts against each other) and either run it in farther or remove it completely.

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9/22/2018 12:52 PM

Looks like the studs loosened as others have said, Tighten the studs down with a set of these Photo
Or lower the head back down and double nut like Ebs mentioned

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9/22/2018 1:06 PM

Ok. Double nut to run the studs down lower sounds like the simplest solution.

Dumb question, but is there supposed to be loctite on the other end of the studs(inside the cylinder itself) to hold them in place? Or are they just inserted and screwed down to a pre-set depth with nothing on the threads? Just asking as I don’t want any future issues after re-installing the head.

Thanks Guy’s!

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9/22/2018 1:15 PM
Edited Date/Time: 9/22/2018 1:15 PM

Should be red Loctite, I would pull all of them anyway and put some on.

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9/22/2018 2:35 PM

It is a defect and may be dangerous to ride. Send me your address and I will come get the bike.

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9/22/2018 4:19 PM

RACERX69 wrote:

Whelp, this one's got me scratching my head. I tried removing the cylinder head today from my sons 18' YZ-250X and ran into a ...more

As suggested before, double nut the studs and run them down so you can get the head off. Then once the head is off, remove the all the studs, wire brush them, apply red loctite and run them down all the way. should solve your problem

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9/23/2018 5:58 AM

RACERX69 wrote:

Whelp, this one's got me scratching my head. I tried removing the cylinder head today from my sons 18' YZ-250X and ran into a ...more

harescrambled wrote:

As suggested before, double nut the studs and run them down so you can get the head off. Then once the head is off, remove the ...more

Or just take the studs out in the first place.

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9/23/2018 7:56 AM

Don’t over tighten the studs. I learned the hard way when I broke part of the water jacket in the head from over tightening a stud.

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9/23/2018 9:32 AM

Studs should be an interference fit into the parent metal, and the easiest way to achieve that is with lock tight. They should also in theory be finger tight, but in reality giving them a little torque is generally necessary. I’d highly recommend a stud pulling kit rather than the double nut method, your odds of pulling the threads and rendering the stud useless are pretty good. If the threads yield, DO NOT reuse the stud.

That clearance on my YZ is also incredibly close, I don’t know why they do it that way but it is what it is.

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