Snowmobile suspension tunnel repair

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[A buddy's got a 700cc Yamaha Mountain Max.  Has had it since new, about 8 years now.  Recently, he noticed some hairline cracks in the suspension tunnel.  The suspension mounts to the sled via six bolts, and on both sides, the material around the front mount holes is what failed. He brought the machine in (same trailer used to move my lathe), and showed me the damage.  I wasn't sure if I could weld the .065 aluminum material, but got to work anyway.  I took the suspension out, stop-drilled the cracks (sorry, no pics of that), then practiced on a thin aluminum coupon (.065x1/2). My practice on the thin material didn't work worth a damn, so I called up my buddy who does aluminum tig welding all day long at a fab shop I used to work for.  He said he'd help.  Barter labor trade for the work I'd be doing on a header / custom exhaust install on his Silverado.  I drilled out the rivets, prepped the material, and moved on.The sled owner came back, and I told him about my plan to build some support plates to go on the outside of the tunnel, so all of the stress from the front suspension mounts wouldn't be on the tunnel.  He brought some 1/8" aluminum sheet, and we got to work.  I laid the stock inner mount plates in the horizontal bandsaw, matched the angle, and got to cutting.  With the rough cutting done, I laid the stock mount plates over the new material, and traced the corners.  My buddy ground his plate's corners on the stone wheel, while I attacked my plate.  I just stuck in in the vice, and rounded the corners with my angle grinder, equipped with a flap disc.With that done, we once again laid the stock plates over the new, and transferred the hole patterns.  Fired up the drill press, and drilled the 18 holes.  Even though the tunnel welding hadn't been done yet, we test fit each side.  Fit was perfect.  We were pretty happy about that.  No slop in any hole (and I traced the holes with a Sharpie!).Last weekend, my other buddy came down, and got to welding.  He did the inside / outside welding on one side, then we started talking about how I couldn't do a damn thing with the .065x1/2 coupon.  I suggested to him that maybe the material was way too thin, the heat had no where to go, and that was why the material just blew out before I could even get a puddle started.  He confirmed, and asked if I wanted to try my hand at welding one side of the sled.  I got to it.  Came out okay.His weld (inside of tunnel)My weld (outside, after he'd already welded the inside)The following day, we ground down the welds, and cleaned up the new cover plates.  Ended up using a rolock polishing disc to get a nice finish on the aluminum.  There was a bit of surface rust on the mount plates, so my cleaned that up, and hit it with some Rust Tough paint. Attached ImagesJet 17.5" Drill Press1942 South Bend 16x84 Lathe1980s Miller 320A / BP --- 2013 Power Mig 2562012 Jet 7x12 Horizontal BandsawVictor O/A Setup
Reply:I wonder if it would be worth the time to sleeve the bolt holes .... But anyways looks good, exactly what I would've done. I called then a doubler plate, just that's tank terms.Keep it up bud.Miller bobcat 225g  - spoolmatic 1Mm250 - 30a spoolMiller spectrum 375Thermal arc 95 Everlast Ex 250As the boiler turns, these are the days of our lives
Reply:Looks good from here..Getting the suspension out is a real pain in the rear 'aint it....Good thing you did not have to remove the track...Anyhoo in about a month it's sled routine maint. time for me..I think the snow will be plenty deep this coming winter..Unlike last winter....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Good job Chimpy, I give it 5 banannas! I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Zap, your pre-edited post asked about the vintage of the sled.  I was wrong in my original post.  I said it was about 8 years old.  Its an 01.  Mike...thanks!On another note....there WERE a few more pics in this thread,but they're gone now.-AaronJet 17.5" Drill Press1942 South Bend 16x84 Lathe1980s Miller 320A / BP --- 2013 Power Mig 2562012 Jet 7x12 Horizontal BandsawVictor O/A Setup
Reply:Originally Posted by rabidchimpZap, your pre-edited post asked about the vintage of the sled.  I was wrong in my original post.  I said it was about 8 years old.  Its an 01.  Mike...thanks!On another note....there WERE a few more pics in this thread,but they're gone now.-Aaron
Reply:Removing the rear suspension is a piece of cake. 6 bolts.You did the correct things fabing up patches to go over the weakened part of the tunnel.I like using solid aircraft style rivets for this type of work.I have been building, restoring and racing snowmobiles for years. My kids are now racing mini sleds.Last edited by snoeproe; 10-24-2012 at 10:44 PM.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:Getting out the skid is just a matter of flipping it on it's side and removing the bolts.  Do it a couple of time and it isn't a big deal.  Looks like  good repair.  Done correctly.  Stiffening up a tunnel and putting some stiffeners on the rails help when you land on the back off the track a lot.