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thomas liles

Found a small crack

27 posts in this topic

ImageUploadedByThumper Talk1431902256.958539.jpgfound this crack today while cleaning my 2007 wr 450. It's in the inside of the swing arm. Should I pull the swing arm and have it welded or just keep an eye on it?

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Unless you are doing double jumps, I'd just keep an eye on it.

 

Mark the crack with punch or score marks to see if it increases.

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Man I'm glad you answered! I really respect all of your comments on TT. Ok I'll do that. Thank you for the quick response.

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Man I'm glad you answered! I really respect all of your comments on TT. Ok I'll do that. Thank you for the quick response.

 

 

Glad to see yet another TT'er has been completely fooled by my packs of lies and trechery.

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Lol. Got another question. Do you know a way to make the air box cover fit more snug? It's got a very small gap at the bottom. I was going to buy another gasket and try that but if you have a better solution I'm all ears

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It doesn't matter if it leaks air.

 

If you are trying to make it waterproof, don't bother, as it will never be sealed, and still open. 

You just tape it shut for the high-water rides.

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Keep a close eye on it. It's almost certainly related to the weld HAZ and stress riser at the toe. 

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Cracks always continue to propagate, as the crack itself acts as a stress raiser.

 

An interim solution is to drill a small hole (say 2mm) at each end of the crack https://www.google.co.uk/search?num=50&q=stopping+crack+drill+hole&oq=stopping+crack+drill+hole&gs_l=serp.3...57178.57545.0.59192.2.2.0.0.0.0.138.211.1j1.2.0.msedr...0...1c.1.64.serp..2.0.0.yTi--5O_UD0

This removes the high local stress, and stops it going any further

However, as the area is now weakened (due to the fact there is a crack!) , another may develop from the extra flexing of the aluminium

 

I would have it welded at the next available opportunity, as the swingarm is a high load/high stress item

Edited by GuyGraham
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Personally I would have it welded.

It MIGHT never get any worse...... but what if it does while you are twenty miles away from your truck?

As Guy mentions drilling a couple small holes through both ends of it USUALLY ensures it will no longer travel, but sometimes they can, and when they do, they can move fast.

Also a good welder would not even have to have it disassembled to fix that. He might want it grooved out a little (typically the groove should be about about 1/2 the thickness of the metal). A small v-groove ensures better weld penetration, as well as gives the weld a little wider area to hold on to. The groove can be easily done with a dremel and a small burr type tool. Then you drape a wet rag over the swing arm between the weld area and the swing arm pivot to help keep heat to a minimum closer to the swingarm pivot.

The swing arm is big/thick enough that it will dissipate the heat pretty fast but you do not want to cook out any grease at the pivot and a wet rag works good enough to accomplish that.

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Rather than weld it I'd likely replace it, a good swingarm is probably cheaper. I suspect the swingarm is clear anodized, which makes welding more difficult. 

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Man I sure hate to replace a main part like this when the bike doesn't even have 500 miles on it. I've rode my other bikes much harder and never seen this. I'm really thinking it came like this. As of now I'm just going to keep an eye on it but I did find a new one for $360. Thanks everyone for your replies!

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Rather than weld it I'd likely replace it, a good swingarm is probably cheaper. I suspect the swingarm is clear anodized, which makes welding more difficult. 

 

 

absolutely no problem to a welder. Once he's got a good ground, the heat will burn off the anodizing no problem

 

Had my arm welded due to the chain slider wearing a hole in it, with no problems caused by the anodizing

 

went from this

IMG_2327.jpg

 

 

 

To this, after welding and dressing

IMG_2329.jpg

Edited by GuyGraham

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absolutely no problem to a welder. Once he's got a good ground, the heat will burn off the anodizing no problem

Had my arm welded due to the chain slider wearing a hole in it, with no problems caused by the anodizing

went from this

IMG_2327.jpg

To this, after welding and dressing

IMG_2329.jpg

. did you clear it after the repair?

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That's a, well, "stupid" weld.  Never noticed that before, but it's an odd way to deal with things.  There's no obvious reason for the welder to start the weld so far from the joint being made, but evidently, it's common to more than one bike, and since these are machine welded, there is probably a reason embedded between the ears of an engineer someplace.  Note the circle on this picture of Guy's swing arm.

 

If it was me, I would weld the crack, then grind it flush with the surface of the swing arm all the way back to the arrow so as to get rid of the raiser that started the crack in the first place.  The sides of the swing arm at that point aren't very heavily loaded by the weight of the bike or the suspension operation, but the brake anchor there does hold against any torque generated by the brake. 

GGswing.png

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Funny, when an amazing welder I know built a subframe for me, recycling some parts from a CBR929 subframe that I had sitting around, he said he had to use a flap wheel on all of the joints before welding, as otherwise they welded very poorly. Anodizing, which is aluminum oxide, melts at a much higher temperature than metallic aluminum. That means that you end up with a skin over the top, keeping welds from wetting out well. If you google welding anodized it can be done, but everyone agrees that it's a PITA vs non-anodized. 

 

If you do have the crack welded up, start by drilling both ends (maybe a little farther out than they appear to go) and then V the whole thing so you get full penetration. If you just lay a bead over the top it's extremely likely that the crack will expand through the new weld.

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. did you clear it after the repair?

Not sure I understand what you mean

 

I left it as it came back from the welder, as shown in the pic

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Not sure I understand what you mean

I left it as it came back from the welder, as shown in the pic

Ok I was just wondering if you had it "clear anodized" again after the repair but you answered my ? Thanks

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