Aluminum or Magnesium

exnailpounder · Mon Apr 20, 2015 6:27 pm

I have a repair to do for a motorcycle shop on a small tab that broke off inside the case on a Honda 250 dirtbike. The owner tells me he thinks its aluminum and I told him I think its magnesium as it is a different gray color than aluminum. He is supposed to find out for me before hand but I always thought motocross bike cases are magnesium. Does anyone know?

zank · Mon Apr 20, 2015 6:39 pm

If you pour a little vinegar on it, it will bubble if it's magnesium.

dirtmidget33 · Mon Apr 20, 2015 6:40 pm

Best thing is to test how it reacts before welding any of these cases. Manufacturers change stuff year to year. You can test it with white vinegar if it bubbles it's magnesium.

Here is a Lincoln video on how to do it
http://www.lincolnelectric.com/en-us/su ... esium.aspx

Edit Zank posted as I was typing

zank · Mon Apr 20, 2015 6:41 pm

exnailpounder · Mon Apr 20, 2015 6:50 pm

Thanks for the vinegar tips

I know its an alloy but its a dull gray color like I have never seen on cast aluminum. I'll try the vinegar test tommorow. I have to use the guys shop tig (syncrowave 200) and he says there is something wrongwith the machine so it should be an interesting day. Is AZ101 a good choice for magnesium?

dirtmidget33 · Mon Apr 20, 2015 7:11 pm

exnailpounder wrote:Thanks for the vinegar tips I know its an alloy but its a dull gray color like I have never seen on cast aluminum. I'll try the vinegar test tommorow. I have to use the guys shop tig (syncrowave 200) and he says there is something wrongwith the machine so it should be an interesting day. Is AZ101 a good choice for magnesium?

curious as to answers on this one. I seem to remember a video of Jody suggesting 101. It really depends on case alloys, never really got a straight answer. Good luck finding out alloy from manufacturer it won't happen even on race car parts they don't like to give there alloy type out. I was told to use AZ92 that's what I used I have some on order as we speak. I believe you will be good to go with 101

exnailpounder · Mon Apr 20, 2015 7:28 pm

Thanks dirtmidget. I have been researching and some are saying the crankcase is aluminum but the covers are magnesium. The more I think about this I might just pass on it. The metal thickness is 18ga. I only have 3/32" tungsten and I don't want to spend the money to buy smaller tungsten, filler, gas lens or collets/bodies for one tiny weld. Plus if I screw it up, a new case is big money. The cost to benefit ratio isn't looking good on this one. I love a challenge but the deck is stacked pretty bad on this one

dirtmidget33 · Mon Apr 20, 2015 7:43 pm

To warn you Magnesium filler is expensive, think stuff I just ordered was $85 or $88 a pound

yeah titanium is cheaper

18Ga is some pretty thin stuff for mag case. Can't say I tried mag that thin yet I know some chain saw cases are that thin. Believe it or not the price of case might be cheaper. After you consider prep time, filler cost, time of repair, cleaning and machining. Lot of times magnesium cases contain gear oil and it's a pain to get clean. I hate gear oil crap never seems to go away. Used to have a rear end puke gear oil on racing shoes Damn I hate that stuff.

exnailpounder · Mon Apr 20, 2015 7:54 pm

This small tab is actually a part of the crankcase itself so I have no room for error plus it IS soaked in oil too. I don't want to buy the guy a new crankcase if things go bad. I'm pretty confident with aluminum but I have never welded anything this thin. I think I will just get his machine welding for him and HE can try it! Going under the bus can be painful

noddybrian · Tue Apr 21, 2015 7:56 am

Given the part is very thin / unknown alloy & contaminated with years of oil soak if it were me I would use HTS2000 - I've had good results using it - the customer is unlikely to know the difference between a true weld & a " braze " repair & so long as it works who cares ? - it will be as strong as a weld or the parent metal & is largely unaffected by contaminants - I don't see the point in chancing welding it - I recently had to repair a radiator off a 997 Sprint - it was paper thin & coolant residue boiled out of it when heated but I made a new pipe spigot & it took to it fine using braze - he's been out & properly " tested " the bike since - worked out fine - I think sometimes there is a perception on a process being the correct one when it maybe there are easier ways - ( & no I don't sell the stuff or have anything to profit from )

exnailpounder · Tue Apr 21, 2015 8:00 am

Hey thanks noddybrian...I just looked into HTS2000 and it looks like the perfect solution. A friend told me that this tab is likely unweldable anyway. I appreciate all the help guys!

noddybrian · Tue Apr 21, 2015 12:46 pm

Hope it works out for you - it takes a bit of getting used to but so long as the pieces " tin " OK then it will work - it's actually stronger than I expected - I always saw it as a poor mans way out of not having the right gear or experience but sometimes it works better than trying to weld - I usually keep a small amount by for jobs such as these - it seems to bond to nearly any alloy - will stick dissimilar alloys together which is useful if replacing a missing part - only downside I found is a rod does'nt go very far so the cost is a bit higher than welding assuming you have everything sitting ready to use - if it saves buying a pound of compatible filler to do just one job then it's still cheap.

exnailpounder · Tue Apr 21, 2015 1:52 pm

I just got back from the shop and the owner was thrilled that I let him know about the HTS 2000. I explained all the downsides of trying to weld oil soaked , paper thin cast aluminum and he agreed and appreciated my honesty. I got hiswelder running great and did some test welds for him and I am going to get all of his repair work and teach him to TIG weld until he feels comfortable enough to do it himself. I always know I can come here and get the right answer and thats what I really like about this site.