Welding Tips and Tricks

Hey everybody, I’m looking to change the coolant spigot location on this cast aluminum motorcycle cylinder. I would like to be sure to not change the critical dimensions of the cylinder(warp) and I’m thinking preheat is a good idea. What kind of torch should I use? And also how hot should I preheat? I am not very experienced with pre-eating as I don’t normally need to with my typical projects. Any advice is greatly appreciated.

Thank you so much!


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If it'll fit I'd use a old bbq or oven if possible.


If not I'd say use a rosebud on a oxy/acetylene rig if you got it. A #6 or 8 should suffice.


As far as temp for cast Ally I'm not too sure. I would assume it matters on the metallurgy though. Someone else will likely come along and fill in that blank.


Hope I've helped

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I’ve got an oxy setup and a rosebud. Great idea. Just don’t want it to get out of control. I’ll practice in a junk cylinder first. Thanks

Even with a pre-heat, the shrinkage of the weld material and resulting draw means it will likely squeeze and distort the cylinder 'roundness' a little on that side even with just welding on the outside. How bad the effect is going to be will be the big question..

I'd say check out the cylinder bore for round-ness and dimensions on various points and record those. Then once you have made the change and it has all cooled back down to ambient, re-check the bore for the dimensions and see if and how much it has deformed.

Bore may have gone a little egg shaped about at the level of the modification or developed a 'squeeze'.

Depending on the outcome it may need a slight re/over-bore and re-hone to get it back to the proper tolerances for your piston clearances.

Bye, Arno.

I don't think you'll see much distortion in the bore due to the construction of that cylinder having internal braces against the outer wall and a separation.

As for preheat, a simple propane torch will be sufficient. Material thickness looks to be about .250? Setup on your AC balance and the frequency will be a greater determination in my opinion. Run a long post-flow to help prevent hot short cracking. First pass, I'd not run filler so you can burn out the embedded crud. Clean that really well, then make a good clean pass with filler.

Thank you for the great tips. I’ll definitely take some pre and post bore measurements and cross my fingers, if necessary I’ll have it replated and honed afterwards. Hopefully it won’t come out of flat on the deck either. Time to dive in!

I’ll do a test on a scrap cylinder to dial in settings for balance and amps. I gather that 4043 is fine for filler on cast so I may use that. I normally use 5356 but I’ve got a bunch of 4043 also.

Concerning cleaning: I’ve had to remove a slight crown in the casting where the work will be and I’ve done that with a burr. The hope there is that it’s down to clean metal now, but I’ll still wire brush and acetone.

ktm550 wrote:Concerning cleaning: I’ve had to remove a slight crown in the casting where the work will be and I’ve done that with a burr. The hope there is that it’s down to clean metal now, but I’ll still wire brush and acetone.

...and heat it up. You'll be astonished at how much crap will float out with your first arc pass.

I had another thought that may help with fighting warpage. If possible bolt it down to a large flat plate And leave it bolted till completely cool


I did that a few months back with a cast intake manifold for a Mercedes and had great results. Mind you I already had a big plate at the shop with holes all over so it wasn't a big deal to bolt it down (old mechanical bonded radiator headers which was steel and 3/4" thick with holes all over)

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Toggatug wrote:I had another thought that may help with fighting warpage. If possible bolt it down to a large flat plate And leave it bolted till completely cool


I did that a few months back with a cast intake manifold for a Mercedes and had great results. Mind you I already had a big plate at the shop with holes all over so it wasn't a big deal to bolt it down (old mechanical bonded radiator headers which was steel and 3/4" thick with holes all over)

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That idea makes a lot of sense. I could just bolt the head to it. But I think I’ll have a plate machined to sit flat across the cylinder

All great ideas!
Cheers

ktm550 wrote:

Toggatug wrote:I had another thought that may help with fighting warpage. If possible bolt it down to a large flat plate And leave it bolted till completely cool


I did that a few months back with a cast intake manifold for a Mercedes and had great results. Mind you I already had a big plate at the shop with holes all over so it wasn't a big deal to bolt it down (old mechanical bonded radiator headers which was steel and 3/4" thick with holes all over)

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That idea makes a lot of sense. I could just bolt the head to it. But I think I’ll have a plate machined to sit flat across the cylinder

All great ideas!
Cheers

I would thinking bolting the head to it would make them both warp together if any warpage did occur.

However I think you'd be better off with a big ole plate of Ally to act as a heat sink.


Curious to know how this works out so keep us posted

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