Alumiweld

I finally did some aluminum build up work on my ZA50 case used with my Gila kit. I've been running this motor without any kind of build up for a long time without any issues. All I did was some grinding to make the piston and cylinder fit and very minimal transfer match porting.  Slapped it together and been blasting ever since (Check out my Puch Pr0n section for some of my adventures in Japan with this set up). It was always in the back of my mind to do some kind of TIG weld build up for the transfers as I did on my Metrakit motor.  Unfortunately I currently don't have access to a TIG or access to someone who can do it for me. What I got instead is some Alumiweld from Harbor Freight. I've read on Moped Army numerous success stories with this stuff for transfer cases build ups. So I decided to try it for myself. The BLUF (Bottom Line Up Front):...

...IT WORKS!!

Here are my experience with Alumiweld:

It took some practice in getting this stuff to bond. I had to develop different techniques to control the weld "pool" during the process. My first attempts were on the insides of the magneto compartment. One focus here was the hole I already made when I ground the clearance for my 21 tooth front sprocket. The goal here was to fill up that cavity so debris, oil, and water don't make it into the magneto compartment. I had JB Weld in there as a temporary fill. JB Weld can be a permanent fill fix like my Metrakit motor build.  But in this case, I just didn't apply it correctly so there was a gap allowing access into the compartment.

First step was to prep the receiving surfaces. I used a carbide grinding tip on a Dremel to scratch up the surface of aluminum. You don't have to go deep.  Just enough to scratch up the immediate surface.  Next step was to heat up the area. I used "camping" propane and torch. This was when the fun begins. I heated up the area and ran the Aluniweld rod through the flame. It kind of acts like plumbing soldier when it liquifies. I filled the cavity up with about half a length of rod and was done. Simple right? NOT!! The chunk of aluminum in the cavity fell off. It took me three trys to finally get it to stick. I found out for myself what everyone on the forums were say that the key to this thing was HEAT. You really need to pre-heat the area by focusing the flame on it for a minute or two before applying the rod. The rod melts fairly quickly but it doesn't mean it really stuck to the surface. The receiving surface needs to be hot enough for the Alumiweld to actually bond completely on the entire surface area. If you get it to bond with little heat, it probably means the majority of the weld you put down is not bonded to the surface area and only a small portion is bonded to a small surface area that is holding the piece on.  What this means that its probably gonna fall off when that area it being held on by gets disturbed during the grinding and shaping processes. I didn't use new rods each time it failed. I reused the aluminum chunk that fell off each time.

The process mentioned above repeated itself throughout the rest of the build ups. I prepped the opposite side of the transfer area in the magneto compartment for weld build up. In a E50, this aluminum build up is a must because when you do the match porting for a the transfers, you'll probably hole through them. For a ZA50, I don't think this build up is necessary for a Gila build. Depending how you go about your port matching. For my Metrakit build, I did hole through. But those transfers where massive. I used JB Weld in this case cause I didn't hole through too much. After doing the initial port matching for this Gila, I found that its possible to get a good transfer match port without holing through. You just have to do it very carefully. Of course I'm not considering the weaken structural integrity of the transfer port walls by matching the big Gila ports.  The walls would be paper thin when your done doing a decent match job. This could result in transfer port wall failure or high heat transfer to the surrounding areas especially the magneto compartment. Adding material in this area would be for that peace of mind.

Front tooth cavity filled. Transfer port partial completed.  Remaining portion prepped.

Hole filled.

The side transfer build up was another adventure. I prepped the receiving areas the same as before.

The weld on the case half shown below actually went on pretty easy. It took me just one try and a rod and a half to build it up enough. I just blasted the area with heat and ran the rod across. I was able to contain the weld pool to the correct spot because the case build up area was flat.  Don't forget to put steel bolts in the case holes for protection.

Prepped and protected

Simple side

The other half of the case was where the adventure began. It took me 4 trys and 3 rods to finally get it right.  On my first 3 attempts, I would blast the area with the propane torch and run the weld. Each time I would have gob of weld ready to be shaped. I don't have a lathe or belt sander or anything so ground the build up down by hand to match the adjacent surface areas (I used a combo of metal files and sand paper with a flat aluminum backing. I used this technique with my Metrakit build with machine like success.).  Everytime I got down to almost smooth, the chunk of aluminum would fall off.  I discovered that the Alumiweld was only bonding to that area because it was receiving the most heat when I directed the torch to it.  On my failed attempts I tried to direct the heat evenly through out the build up surface area with zero success.

Failed attempts

Initially looked good.

Nope!! Bond about to fall off!!!

My solution: I changed the tip of the propane torch. I attached a tip that concentrated the flame to a more narrow area. I now could control the areas I was heating up. It also provided a hotter flame so the entire area on the case remained hotter. On my fourth attempt, I scrapped the previous chunks I was reusing and used a fresh rod. Wouldn't you know it went on with a strong bond with that try.

Propane Kit

Hot tip!!

Attempt #4

Success!!

Some purosity

Simple side no problems.

I have a few Lessons Learned from this process:

1) Clean and prep the area well.
2) HEAT!! This is key!! I think mapp gas as everyone suggested would work best because its more focused and hotter than propane. But a propane narrow tip worked for me. Also, pre-heating the piece in an oven would definitely help.
3) For build up type work, focus on getting an initial layer on the receiving surface first. Make sure you get this bond on the entire surface area your trying to build up. After you lay down the initial layer, the next layer would be on the Alumiweld layer. This layer doesn't require as much heat to melt the surface to pool and bond it with new weld. I found that this technique is the best when laying down build up weld. But make sure it pools up with the surface of the old layer and new weld or else you gonna get voids or porosity.
4) Be careful not to reheat areas where you already laid down a good bond. This could cause the weld to fall off. If you got multiple build up sites, plan them in a logical order to prevent this.
5) Protect any holes or anything else with steel. This stuff don't bond on steel.
6) Use a steel screwdriver or similar to help you push the weld pool around. I used a screwdriver to help shape the weld while heating it up.
7) Do this repair in a dark place in order to see the flame. I did this at night under lights cause I could see the flame and exactly where I was focusing the flame too.
8) Alumiweld is reusable. If you wanna be cheap, reuse the weld that fall off or you screw up with. Easily melt-able back together into one big heap of weld goodness.

That's all for now. I think Alumiweld is a good option than TIG welding for weld case build ups. It's a better option than JB Welding or epoxies. If you have any questions, hit me up on comments or email me. I'll post the finished motor when its done.

Happy Tuning.