Found a crack in the top motor mount brace.

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#1
Has anyone else encountered this type of problem? I have a YZ 125 and the bracket on the frame that the motor mount attaches to has a crack on the top forward most point on the bracket that is welded to the frame. I would show a pic but i'm too new to be allowed to post an attachment. I just wanted to know if it's somewhat common or I'm screwed...it doesn't look to have cracked anywhere else. Just around the one bolt.
 
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#2
Stop riding it and have it welded up before the crack grows. It's not a serious problem, but the crack may continue to grow making the repair difficult.
 
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#3
My son's 03KX125 Had a similar problem. Cracked mount caused a vibration at high rpms. Ordered a new one. The swing arm and other engine mounts were loose, this may have caused the upper mount to crack. Make sure all engine mounts are tight.
 
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#4
Is this crack in the frame or the mount? If it's the mount, just buy a new one. If it's the frame, do as I said above. I've chased my share of cracks in a Kawasaki frame, we let one of them run and learned our lesson the hard way. I had to cut all of the gussets out because the crack extended all of the way around the tube.
 
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#5
MotoCruse said:
has a crack on the top forward most point on the bracket that is welded to the frame.QUOTE]


Frame cracks are not uncommon on older bikes and bikes that are ridden hard. Like snb73 said, loose motor mounts will also cause a mount to crack.

There is more to welding up a frame crack than just welding it.

To repair it, strip the paint from around the crack and find the end of the crack. Take a small drill and drill a hole in the end of the crack. This will stop it the crack from extending further. Then, take a grinder and grind the crack to a vee. Grind about 90 percent through the the thickness of the frame but don't make the vee too big or go all the way through the metal. Then, take the frame to a tig welder and have them tig weld it using mild steel rod. Don't use a torch or an arc welder since these weld too hot and will cause the metal around the weld to become brittle.

Sometimes after you weld up the crack it will help to gusset or glove the frame in the area of the crack. This involves adding a small metal gusset or wrapping a piece of sheet stock around the frame and welding it. If your frame is 4130 chrome moly, you will have to stress-relieve it after welding. You do this by heating the area of the weld to a dull red glow, aprox 1250 degrees F. A bright red glow or cherry red is too hot. Bring the heat up slowly and evenly around the welded area and then let it air cool in still air. Do not quench it with water. You can purchase a small crayon looking thing at your local welding supply called a Tempelstick. These come in different temp ratings and will tell you exactly when you get to 1250 degrees.

Good luck. :cool:
 
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#6
I'm not sure if the frame is the Chrome moly. Where do I find out that information. I have a "Clymer" manual that I'm referencing.
 
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#7
MotoCruse said:
Has anyone else encountered this type of problem? I have a YZ 125 and the bracket on the frame that the motor mount attaches to has a crack on the top forward most point on the bracket that is welded to the frame. I would show a pic but i'm too new to be allowed to post an attachment. I just wanted to know if it's somewhat common or I'm screwed...it doesn't look to have cracked anywhere else. Just around the one bolt.

I had the same problem on my cr250, but they both completely snapped. I baught 2 new mounts for 26$ and volia . My other engine mounts were also loose.