HELP!!....Yam YZ465 frame problem

wfoyz250
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wfoyz250
Edited Date/Time 1/26/2012 9:18pm
Hey folks, I am having a little problem with the frame on my '80 YZ465. Earlier this year a horizontal crack developed on the downtube, on the surface of the reinforcing saddle, adjacent to the shock reservoir. I had the crack welded and thought everything would be fine. Well after 10-15 hrs of riding, an identical crack has developed about a 1/2" lower (on the saddle) than the previous one that was welded.
I'm little puzzled why it's cracking on the reinforment saddle. Placed a straight edge along the downtube and it is straight. Hate to have to get another frame but I sure would like to know why this problem has occured again.
Any idea's?
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newmann
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newmann 7/17/2011 7:40pm
7/17/2011 7:40pm Edited Date/Time 7/17/2011 7:41pm
Typically a crack will occur when the metal has been stressed to the point that has become brittle. Welding the crack doesn't repair the fatigued metal around it. Find a way to fabricate a sleeve or gusset of some sort to go beyond the area close to the crack. Weld up the crack, grind smooth and gusset over it. Got a pic?

My 81 YZ250H had a small crack on the top tube directly behind the steering head. Check there too!
wfoyz250
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wfoyz250 7/17/2011 8:23pm
7/17/2011 8:23pm
I'm wondering how the saddle can crack, afterall it is welded along either side of the downtube. Wonder what the tube looks like......
captmoto
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captmoto 7/17/2011 9:55pm
7/17/2011 9:55pm
Poke along the frame there with a small phillips screwriver and see if you poke through. I had that going on in the main down tube above the shock res area that turned out to be rust from the inside. The screwdriver test ended up making it look like swiss cheese.
wfoyz250
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wfoyz250 7/18/2011 5:05am
7/18/2011 5:05am Edited Date/Time 7/18/2011 5:06am
Here's a reply from a fellow over on the Vintage swapmeet site.........
Between 80-81 yz250's and 465's I've owned, at least 10,....... EVERY one of them was cracked where you are talking about.

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bultokid
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bultokid 7/18/2011 5:33am
7/18/2011 5:33am
Yikes Larry, sorry to hear that, guess better check my closer. I can just hear my step-dad 30+ years ago " I told you not to buy that Jap junk with it's pos cheap metal" So I bought a '79 Bultaco and it was the biggest turd I've ever owned.
bultokid
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bultokid 7/18/2011 5:34am
7/18/2011 5:34am
Hey did the springs workout for you ?
wfoyz250
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wfoyz250 7/18/2011 6:53am
7/18/2011 6:53am
Hey rhett.......missed you out at Rio....I had the funds for the springs. They worked better than the stockers. I have emulators on order to add more adjustability.
bultokid
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bultokid 7/18/2011 8:31am
7/18/2011 8:31am
Would have loved to be there....baseball.....going to order some emulators myself. I've had them on several bikes work great.
Racerx930
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Racerx930 7/18/2011 9:11pm
7/18/2011 9:11pm
I was the one who replied to you over at Mark's. I have 2 of the frames right now in the garage waiting to get welded up. A buddy of mine told me they crack like that from being ran without the head stay at some point in time.
wfoyz250
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wfoyz250 7/19/2011 4:39am
7/19/2011 4:39am Edited Date/Time 7/19/2011 4:40am
Interesting. I've had this bike for a year now and both cracks have occured with the head stay in place.
What are you having done so it doesn't happen again? I'm thinking of a some sort of half-round stiffener welded to the opposing side on the downtube.
MOgle80
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MOgle80 7/19/2011 12:56pm
7/19/2011 12:56pm
I had my frame reinforced at a race car frame fabricator that happened to be right up the rode from my work...Jake's Performance Chassis in Lee's Summit, Missouri. Took the cracked material completely off and made a piece very similar to replace it
wfoyz250
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wfoyz250 7/19/2011 3:29pm
7/19/2011 3:29pm
That idea crossed my mind too. There's a circle track shop that's close to my area so i may just do that.

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