Restoration of Sandcast #97

[Wayne]

Mark
The hole on 748 does not come right through. It is however drilled through the top wall and into the bottom wall of the cross bore.

[markb]

So do we have another distinction between early and later sandcasts?  Why does the hole in E100 go all the way through?  And what are these holes for?    Anyone?

[markb]

Steve, maybe this would be a good question for Bob Jameson.  Is it possible that this was for a design feature that was eliminated or something planned for future models that was never used?

[markb]

So I had this crazy thought.  When I was using the torch to help remove studs and screws from the cases, I noticed some kind of moisture forming in the area around the flame.  Could this be water or something leeching out of the aluminum?  I haven't had any paint stick problems with my diecast or sandcast that was painted but I've seen posts from guys who have used the same paint and did have problems.  In both my other cases it was months before the assembly was completed and subject to heat and oil and gas so maybe that was part of the reason for my success.  Maybe too because they hadn't sat outside for over 20 years.  But what would you think about putting the cases in the oven at 250 degrees F. for a couple of hours to "dry" them out before painting?  Actually I know my painter puts them under a heat lamp before painting but I'm sure they don't get that warm.  Any thoughts?

[Wayne]

Mark
Right from the Dupli-Color-Specialist as I had some questions regarding whether or not it was necessary to completely strip my cases.

As long as the surface is free of flaking paint, oil and grease. From what it sounds, you have the surface well prepped. You might want to heat up the aluminum a little prior to painting. You can do this with a heat lamp or even a halogen light.

In the past, I have heated engine cases up for various reasons. Installing bearings comes to mind. I drop the case in the oven at 300 deg or so for a while, put the bearing in the freezer and it will drop right in.

I plan on doing a little baking of my cases in the wife's oven prior to paint. I have used a lot of cleaners and solvents. I would rather eat them than have them bubble out of my freshly painted mill! 

[Steve Swan]

Mark, what was the temp of the cases ?  

What type of a flame (gas) were you using ?

Not uncommon to see surface condensation form at room temperature, caused by the high temp of the flame rapidly heating the cool/cold cases.  Higher relative humidity increases the incidence of this phenomenon; condensation cannnot evaporate as quickly when there's higher relative humidty.

Condensation forms when two mediums have temp differences, typically when one medium is dense (metal) and the other medium is much less dense, (oxygen/propane or O2/acetylene.  

Same reaction as fog formation, i.e., warm air meets cold earth or a cold engine condensing water as a by-product of combustion.

There is no water inside the metal.

[markb]

It was a propane torch.  Makes sense.  Any thoughts on my other question?

[Steve Swan]

I painted E2241 cases on a hot summer day, let the cases sit in the sun for a couple hours.  Oven will work, i have not tried oven for painting, prob.only need to heat at around 150' - 200' for an hour or so. 

[Riccardo]

My painter says:

the best thing is to paint in a dry day.

[markb]

I pulled out the covers today to work on.  I’d like to get them done before I need them.  I hate this part.  I guess hate is a little strong.  Yea, I hate this part.  Anyway, I came up with another challenge.  And more questions.  I didn’t see this until I started sanding on the rotor cover, but I have a small crack   on the cover.  You can see there are quite a few good dings in it too but I’m hoping they will sand out.  But there’s a pretty good dent and that’s where the crack is.


Here’s a better view of the crack.  It’s visible on the inside too.  It doesn’t appear to have been leaking but it seems like I should do something about it.  So here’s the questions.  Would repairing it using JB Weld or welding it on the inside be sufficient?  Is it possible to fill the dent with weld or will there be a problem with the color of the aluminum matching?  Should I sand enough to remove all the blemishes or if a little is left is that OK.

[Steve Swan]

Poor old #97 lived a full life.........  She was ridden hard and put away wet, literally.  Hmm, the challenges of working with old used parts.  Judging by the looks of that alt.cover, there are marks in it no amount of polishing will eliminate........ ??  But the cover will look ALOT better after you are finished with it than it does now.   The good part about "it" is, when the restoration is complete, the small blemishes left in the cover will be overshadowed ("drowned out") by the magnificence of the completed machine.  It's always hard, with our critical eye, when we focus on one part and know every last blemish of each and every part, these things always stand out and look worse than when the machine is assembled  and these small things fade into the completed project.  As Chris says, there's always some compromise involved with decisions we make.  Myself, i would dress down as best possible the external crack, perhaps explore some aluminum filler to help hide the outer crack.  The good part, the crack is on the under side.  The inside, i would rough up with a Dremel, then JB Weld.

[Riccardo]

I agree with Steve.

If you see a little ding with a magnifiyng lens, for sure, you will see a big hole.

The small external crack, for me, needs a welding job.

[markb]

Yes it's kind of sad she was so badly abused.  I'm glad this wasn't my first project.  I probably would have given up by now.  But when she's up and running again, I promise, I'll treat her right. 

[hondasan]

I had a cover just like yours - small ding which had cracked. The guy that welded that one did a real good job. He filled the ding from the outside, and ground out the crack and welded from the inside.  I was then able to buff / polish the outside.
When you get real close to it (as we do during restoration), you CAN see a "shadow" in the alloy which is the different composition weld filler material. When it is on the bike, it CANNOT be seen / noticed unless you are laying down next to the bike. Not perfect, but an acceptable compromise on that occasion.


Chris R.

[markb]

Thanks, Chris.  I was hoping I would hear that.  I thought these things only happened to me.     It makes me feel better to know I'm not the only one.  I've got a non-sandcast cover that I was thinking of giving to my welder to play with.  I agree it's a compromise but the color difference to me seems better than the dent.