Yamaha XS 650: original steering stem on Yamaha XS 750 upper and lower clamp

[expercat]

Hi!
my first thread on XS 650.com!!!
I write from Venice (Italy). I have two Yamaha XS 650 1974.
I have always found the original front legs (34 mm) a little weak.
So on one of these bikes, I thought to swap the triple tree with Yamaha XS 750 triple tree (36 mm).
I know it's not an original idea becouse other Yamaha XS 650 fans made this project.
Now I solved many problems of this operation and I have to weld the original stem (using a lathe I cut the original welding) on lower Yamaha XS 750 clamp, after pressing the stem on this clamp.
My question is: which type of welding and which type of welding material do I have to use?
My fear is to do a too hardened welding an therefore to have a fragile welding.
Thanks for any help.

 

[gggGary]

As long as your filler is mild steel and you get adequate penetration (heat) you should be good. I have used a mig to do that with no issues.

 

[expercat]

As long as your filler is mild steel and you get adequate penetration (heat) you should be good. I have used a mig to do that with no issues.

Hi!
first of all thanks for your kind answer. I apologize for my long silence but I wanted to investigate every side of this swap. Infact we have a critical welding.
So these are the results of chemical investigations on lower brace (from Yamaha XS 750) and stem (from Yamaha XS 650) by destructive tests on two items.
STEM
Method Felast
Fe% C% Si% Mn% P% S% Cr% Mo%
98.26 0.364 0.342 0.733 0.0144 0.0289 0.0994 0.0056
Ni% Al% Cu% Ti% V% Nb% W% As%
0.0262 0.0344 0.0487 0.0021 0.0059 0.0012 0.0045 0.0102
Sn% Co% Pb% B % Sb% Ta% Ca% Ceq%
0.0018 0.0086 0.0002 0.003 0.0064 0.0015 0.0002 0.514
PCM%
0.421
LOWER BRACE
Method Felast
Fe% C% Si% Mn% P% S% Cr% Mo%
98.95 0.237 0.234 0.437 0.0211 0.0185 0.0253 0.0052
Ni% Al% Cu% Ti% V% Nb% W% As%
0.0157 0.0118 0.0137 0.0009 0.0040 0.0014 0.0051 0.0030
Sn% Co% Pb% B% Sb% Ta% Ca% Ceq%
0.010 0.0049 0.0003 0.002 0.0077 0.0001 0.0003 0.319
PCM%
0.270

Now after these cold data it's necessary an operative translation.
For the stem a possible classification is C35 by UNI EN 10083
while for lower brace it's not possible an exact classification becouse its fusion is in conformity about ten steels.
However, for welding together stem and brace it's better to use TIG and first 309 filler where there was the original welding (first passing) and then a second filler SG2 (second passing).
It's better a pre heating to 60/70° Celsius and slow cooling after welding.
I hope everything helps other crazy guys like me.
Rergards.
Mike

 

[gggGary]

Or use MIG, "no doubt" how the factory did it.

 

[TwoManyXS1Bs]

Expercat, Wow, fascinating. The lower brace has much lower carbon than I would have expected, being a casting.

Would love to see similar testing results for the various aluminum alloys used for these engines. Many members wonder about weldability of engine cases, and we suspect varying levels of silicon that was used to improve flowability of the early casting methods...

 

[expercat]

Hi!
first of all I want to apologize for my English. I write from Italy.
OK! The metal investigation is really fascinating but.....very expensive.
For two items (lower brace and stem) I spent about $ 180 plus the cost of material which has been destroyed. The engineers who made this investigation cut both the items.
Of course I didn't destroy the stem and lower which I'll install on bike but another couple which I bought on eBay for this target.
If I'll manage to have a cheap price, I could make an investigation on engine cases but I want to remember that these tests are destructive.
Best regards.
Mike

 

[gggGary]

expercat it would be wonderful to do this with crankshafts and crank pins...........

LOL thanks for the hard work and report.

Il tuo inglese è molto meglio del mio italiano!

(thanks to google)