Aluminum Weldability -CR 250 Trans cover

[Aerometalworker]

Ive never had any issues with bike parts. Last cover I checked had somewhere around 12% zinc ( easy to believe with a die cast part ). 4043 or 4047 were appropriate in that case. One of the best investments I ever made was getting an ultrasonic heated cleaner to rattle aluminum castings clean, its a night a day difference. Always used one at work....finally had to shell out for one.

[MR.57]

OMG!!!!! Is there a JB Welding forum out there???? Any crap that hinders welding stops good epoxy adhesion as well.
If you only knew how much of that CRAP I have removed by folks with good intentions only to find they have simply making the job they should have done in the first place much more dificult.

FK if you've got the "secret sauce recipe" for Honda's motorcycle case alloy I'm all ears. I've had good results with H-D and Kawasaki, but Honda seems to be a different animal.

It corrodes to a Dark gray like Magnesium, but it isn't Magnesium. How do you correctly match a filler when you have no idea what alloy it is? Honda does occasionally use pure Magnesium for outer case parts on their racing bikes (HRC), but this was a factory part.

[Portable Welder]

Aerometal worker please elaborate about yor little machine, What size part does it hold.

[FusionKing]

FK if you've got the "secret sauce recipe" for Honda's motorcycle case alloy I'm all ears. I've had good results with H-D and Kawasaki, but Honda seems to be a different animal.

It corrodes to a Dark gray like Magnesium, but it isn't Magnesium. How do you correctly match a filler when you have no idea what alloy it is? Honda does occasionally use pure Magnesium for outer case parts on their racing bikes (HRC), but this was a factory part.

Seriously I haven't had much trouble with bike parts either. The main thing I do is after clean I run a puddle on all the edges of the crack and re-brush any crud that floats to the top. Then flow again and if the puddle is shiny, then it is fine to weld. Mag or aluminum either way. Just the mag ones are a bit scary IMO because I don't do it everyday but actually I have had great luck on mag parts for years. I like to use sine wave on castings and keep the balance and hz down as well to take full advantage of the cleaning the machine can do.
4043 is all I've used on almost all those and seriously I don't recall the mag rod I have had forever, but it is very expensive.
Now all that said I'll give you a bit of wiggle room here. I have done bunches of Honda stuff but I may have never done the exact case you are referring to.
From my perspective, if a guy brings me a part, I am gonna do my dangdest to get his money. We did have one local welder that would weld your pontoon and then coat his work with JB. I pretty much took every customer he had that hadn't run him off.
I truly wonder if that cast was very high in mag and if so how a mag richer filler would work. That I have NOT tried but as of yet never needed to. I cannot find anywhere something like 5356 is recommended for a casting, altho I have heard people speak of it. Temp would make it a problem anyway.
You can bet I will be looking specifically for a CR250 repair now just because I am curious. I fix loads of their other stuff. Like outboard lower units, PWC engine parts, and small motor and ATV engine stuff.
BTW, I'm never sure what any casting I am dealing with as far as actual composition. It would be nice to know but seldom practical to pursue on my part.
If you (or anyone) finds Honda's composition info on this I would love to here the answer myself. Always looking for an edge.

[zmotorsports]

MikeDogg, this is not a bad repair if you take your time and don't get in a hurry. I do quite a few of these on bikes and especially ATVs where the front sprocket is close to the transmission/engine case. The clients will try to skimp on chain quality and/or maintenance and the chain will break and wedge between the sprocket and trans and blow a hole in the case.

Usually the customer will still have the piece or it is somewhat still attached and can be put back in place with little effort. Sometimes I have to fabricate a new piece to fill the void.

Either way cleanliness is the key. I haven't had the best luck of V-ing the already thin casting. I generally clean in the solvent tank after disassembly, spray with a non-clorinated (make sure it is non-clorinated) cleaner, lighlty run a Roloc disk over the area to remove the surface irregularities and then I will use a heat gun to try to extract as much oil from the casting as possible.

I then make a small bead alongside the crack preferably on both sides to "float" the impurities to the surface. One thing I have had great results with is to set the machine to pulse at a high rate if you have access to an advanced squarewave machine. This greatly helps to get the impurities to the surface. After making the preliminary passes, wire brush the surface very well and then fuse the area together generally 4043 rod seems to work the best.

Also, depending on the size of the case half (some are quite large and do a good job of dissipating the heat and others are very small and can warp fairly easy. If the part is on the smaller side I clamp it to my welding table to act as a large heat sink and also to help it hold it's shape with less chance of distortion.

After the part has cooled and the repair looks solid I run it across some sandpaper that I tape down to my surface table and lap the part to make sure it is perfectly flat. No sense in going through all that work on one leak and create another.

Good luck, Mike.

[bob_e95482]

I just welded a Kawasaki cylinder head, with excellent results, with my Dialarc HF.