Tig welding crankcase. Access problems. Any ideas?

[Argonman]

Hello everybody. Recent lurker as I’ve been teaching myself tig welding over the past couple of months with the aim of repairing an old Suzuki motorcycle crankcase which was damaged when a big end bearing let go. I’ve made a start and as expected, welding low-quality oil soaked (50 years) cast aluminium has not been easy. But I’ve made some progress. Now I’ve hit an access snag.

I need to weld both sides of the threaded boss at the base where it is cracked. Two problems. Firstly in order to get down to the crack i need to extend the tungsten, almost 1” protrusion. Being a learner this is not ideal. Also when i strike up an arc it is reluctant to go where i need it. It is attracted to the walls of the boss or the walls of the cooling fins. Ideally iwant it to strike the bottom of the trough so i can build up weld between the boss and fins.

Any thoughts or suggestions? Regards. Chris

 

[addjunkie]

Cut fin away, repair what you need to, rebuild fin

 

[hotponyshoes]

Block up the gaps at the ends of the fins with tape/bluetac/tinfoil/whatever
Set a load of preflow and purge the area with argon then you should be fine with 1" of stick-out

 

[oldbikedavey]

Cut fin away, repair what you need to, rebuild fin

Better still, don't rebuild the fin.
Much more trouble than it's worth in overall terms.

 

[Popcorn]

You need some extra long ceramic cups you may need to go down a size with your torch depending on what it is

https://www.amazon.co.uk/RIVERWELD-796F72-796F73-796F74-796F75/dp/B01MEHKSR3/ref=asc_df_B01MEHKSR3?mcid=7b0073dafef936f39ce9802baac3c973&tag=googshopuk-21&linkCode=df0&hvadid=697276023079&hvpos=&hvnetw=g&hvrand=11662915987453356925&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006816&hvtargid=pla-1722007260937&psc=1&gad_source=1

 

[Argonman]

Sincere thanks for your replies. Some really useful comments & advice which will help me decide my next steps. I’ve been putting off any further attempts for fear of doing something stupid but nothing ventured nothing gained. I’ll probably have a go this weekend and of course will post the outcome. Please don’t let this make you avoid making any suggestions.

Regards Chris

 

[Fazerruss]

What bike, GT750 by any chance?

 

[Argonman]

What bike, GT750 by any chance?

Yes. That’s right. Chris

 

[Fazerruss]

Yes. That’s right. Chris

Thought I recognised that style of casting, I've done that many!

 

[Argonman]

Just a small update. I decided to cut down the fins to improve access. Photo shows improved clearance for torch without excessive tungsten stickout. Still a pig to weld. Not helped by frequently dipping the nozzle or touching the exposed shaft of the tungsten on the workpiece. I tried the silver foil routine to reduce dead space. Seems like a cheap precaution and costs very little. I also like the extra long cups that were suggested. Maybe something to consider for the future but i need to crack on now.

Some progress with the weld. Will finish later this week.

Once again thanks for the support & suggestions. Regards. Chris

 

[minimutly]

I suggest a die grinder for cleaning up
pre, during (if things go wrong) and post welding

 

[Argonman]

I suggest a die grinder for cleaning up
pre, during (if things go wrong) and post welding

Yes. Thanks. More a case of when things go wrong. It’s been a slow process. Weld, contamination bubbles up, holes appear. Grind it all out and start again. Numerous regrinds of the tungsten. Learning all the time. Trying different settings. Watch the pound notes float into space as the argon gauge falls lower and lower.

That’s the price of stardom

 

[Popcorn]

Next job is to weld the top of the cooling fins back on