Prepping a 37 year old, oily engine case for TIG welding

contact cleaner works pretty well

Real contact cleaner cuts through just about anything.

I don't know of any problems with contact cleaner specifically, but be very careful with other similar products.
Some people use that term interchangeable with brake parts cleaner and other spray products.

Welding on parts that have been cleaned with chlorinated brake parts cleaner can release some very strong toxic gas.

 

If you plan to strip the engine case down and clean it thoroughly, I think heating them after cleaning is a great idea.

A hot wash cleaner is by far the best way to deal with oily aluminum parts.
The industrial cleaners used by automotive shops are basically a large, heavy duty dishwasher with aggressive soap.

I have had good luck with the ZEP brand degreaser (it's the purple concentrated liquid) and hot water.
I would bet Oxy-Clean Stain Remover would work well.  I believe some guys on the forum use that to clean No-Toil air filters.

Some of those heavy soaps can attack aluminum, so your best bet is to scuzz brush the parts with them, then rinse it off thoroughly.

Yes ,If you are going to strip it down

Box the entire engine up & send it to TMR……it won’t be a budget build any longer but it will be 100% correct…

For larger areas to be welded, soaking case in acetone is the method approved by a welder competent enough to successfully repair clutch actuator bores behind countershafts. 

Find someone in your area with a laser cleaner, that engine will look as good as new.

clean with contact cleaner then heat it with MAP gas (yellow bottle) and get it about 250 degrees this will get a lot of the oil out, then weld away

Certainly.

But, if this is the only weld repair you've got on your hands, well, it's pretty simple.

It will not be like an oil carrying / holding piece of broken case, where oil can have Really been penetrating into the 'pores' of the material. 

 Of course, you'll have, probably, chain lube deposits etc to deal with, but, thorough cleaning and prep of that area will be pretty bloody easy to to.

And I DO Mean THOROUGH cleaning.

Prep Before Weldment, IS the Key!

It appears you've got the Post, with a 'good / clean' break to it, and, the case at the break looks like a neat 'match' to the post remnant.

And, there's thread in the case.

So, I'd get a bolt that is long enough to key into the threads that are in the case - and, you should check how much depth there is to the case, to see if you can tap the thread deeper into the hole, to use as long a bolt as possible ( and, to use After the repair, so as Not to have the bolt 'hanging' after the weld).

You  should be able to thread the longer bolt through the thread in the post, through the thread in the case, to hold the post straight / correct to the case. 

If you can, I'd recommend having the repair done with the cases bolted together, and the bearings nearby, in the cases. 

A skilled welder can then do the repair. 

I've done repairs with the bolt insitu during the whole weldment, but, that's risky, as you could find the bolt then 'trapped', which would be a disaster - but, I've never had it happen. Best to do reasonable tacks, then remove the bolt.

I'm a Welder / Maker of over 5 decades experience, I've done Hundreds of case repairs in all those years. They are Far from my favourite thing to do, but, I've done them, as needed.

queen of spodes : I'm half a World away - Australia.

Do the cleaning and Prep yourself, try the bolt set up I suggested, and find a Experienced / Good TIG welder.

Prep is the time consumer, with most repairs. Present a Job to a welder, pre-set up, and it's much less of a 'bother' to them. 

Note, I did miss out on a  part of  'prep' - if You've a Dremel,  Emery Paper / Files, to  deburr / prep the weldment areas, that makes it even easier for a welder to deal with , and  for them to do Do A Neat Job.

Enjoy your Rebuild / Rebirth of a fine, older bike!. 

Everyone's going great advise. 

I'd disassemble,  hit it with dawn dish soap and a scrubber get the most crud off. Vapor blast it. Acetone soak it and brush it. As for heat thats for whoever welding it to me as thats the last thing I do usually as im getting ready to weld. But yes map gas/yellow tank.

I use to when I worked at a machine shop take a couple rods and tap them for 8mm, 10mm, 12mm bolts. Then I could machine them and grind them down to the OD I needed. Run the bolt through the slug into the part then weld it or tack weld it if i needed to remove the bolt to weld it. 

But as I think bearuno said. Clean it up completely and make it ready for welding, prep the break a little with some emery, dremel ect. 

An take it to a local welder woth a bolt for it and let them do it. Even in illinois you can find a shop that will do it for 50-100

Ive welded drain plugs with the cases assembled.   Brake clean, then propane torch (not map gas) then brake clean again.  Not rocket science.