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Hello all,

Quick question here. I have an older sportsman 90 that I picked up for $600. It is in pretty nice shape for its age. I have it partially stripped down to check for problems, etc, and discovered a crack in the upper tube on the frame. I know this is a common issue in the atv community. I tinker with things like this on the side for fun and have done so for years, mostly with amphibious six wheelers. One thing that I don’t have in my arsenal is welding. I am currently taking a tig welding night class and plan on taking the mig one eventually. I wanted to take one of these classes to get a general idea of what I’m doing before I dive in and learn bad skills. Anyways, enough of that, here’s my question:

I want to repair this crack the “correct way.” But first, is there actually a “correct way” to fix this? I showed these pictures to the instructors of my class and they were talking about me having to cut that section of frame out and to add in new metal, etc. That seems a bit extreme to me for this little 90cc wheeler that will never see over 10 mph in my yard. I am a picky person with attention to detail and DO indeed want to learn how to make repairs like this the correct way and not just to cob shit together. From everyone’s experience on here, how should I go about repairing this crack? I’m pretty sure it’s the only one on the frame…that I can see anyways.

I do not have a tig welder yet. I do own a mig welder that I purchased with my employee discount before I left my auto parts store but haven’t used it yet. I did take a one day mig course and would feel comfortable enough practicing with that and then using it to repair this eventually

I appreciate any suggestions/help! Thank you!
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Clean up around the crack to get rid of all of the rust and paint without digging into the material thickness too much as the wall thickness of material on a frame isn't all that great.
Take your MIG and set it up on material with the same thickness of the frame tubing and practice a bit so you get a feel of running a good bead..
Secret is getting decent penetration without burning a hole through the tubing - but even if you do go through it, it can always be stitched up easily regardless, something like darning a hole in an old sock! ;).
If you find running a continuous bead hard to do - just stitch the crack up with short spot welds that slightly overlap and it'll do the trick just fine.
The crack doesn't appear to be in a spot that is too stressed or important, so just take your time and don't get any area of the welding area too hot and I'm sure you can do a great job.
Additionally, the closer to the crack area that you can clean up a spot for your ground to clamp to - the better you will find the actual welding process will work out and it's a good idea to remove any connections to a battery if the bike ahs one, before you start welding as well..
Remember - it doesn't have to be a 'stack of dimes' pretty TIG - type of weld to do the job and be strong!
 

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That crack is no big deal. Why in the hell your instructor would tell you to cut out material and replace it with new is beyond ridiculous. He has no clue.

Clean up the area with a wire wheel or light grinding to get rid of the surrounding paint and any rust in the area. MIG or TIG welding the crack would both work. I would MIG it if it were mine. No need to drill a hole at the start and end of the crack. The weld will fix the issue and prevent spread of the crack. If you are unsure of your ability to weld it, take it somewhere to have it properly welded (muffler shop or body shop may be able to do it). It shouldn't cost much at all.
 

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I use an acetylene torch and fusion weld frames using mild steel wire as filler - of course you still need to clean the cheap Chinese steel before any attempt to weld, but fusion welding burns off paint and rust as you progress. I use the mig primarily for bearing race removal and the stick welder for heavy materials. TIG is fusion welding with an electric arc instead of a gas flame.
 

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Yep. Just clean it up. Practice on a piece of similar scrape metal to get your heat and wire feed set correctly and then weld it up. Let it cool a few minutes, clean up the weld and then spray a little black gloss Rustoleum on it... Done.
 

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Yep. Just clean it up. Practice on a piece of similar scrape metal to get your heat and wire feed set correctly and then weld it up. Let it cool a few minutes, clean up the weld and then spray a little black gloss Rustoleum on it... Done.
Its thin tubing and unless he has thin tubing to practice on he will be burning holes through it in no time and then he will have real issues. He might want to find a good setting and pulse weld it with the MIG.

This really isn't a good project for a newbie welder.
 

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Yeah, that thin tubing is sometimes hard to do without burn through even if you weld quite a bit. Just a series of spots alternating top/bottom/top/bottom etc. will stitch it up just fine too. Its really not that hard.
 
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