I repaired a snapped off lug on my Gen 1 radiator with Technoweld but like you I found the pencil blowtorches just don't get it hot enough to get the weld started. The whole radiator is a massive heat sink so it soaks a lot of heat up. Use a proper blow torch and go easy. It works like a charm when you get it right and you can reheat it and move it if it's not in the right position.If the weld doesn't hold, it will be because of corrosion. Mine eventually became so rotten it just wasn't worth the effort - you can't weld corrosion! So I bought a cheap radiator on eBayRadiator Cooling Aluminum Replacement for YAMAHA FZS1000 1998-2003 99 00 01 2002Definitely not as well made as the Yamaha OE (it's 80 quid, not 400) but it's been on the bike for 20k miles now, so it works. Luckily, there are many more fans than radiators on eBay, so it's usually not a problem. And R1 fans are the same, you just need to keep the original mount/surround and bolt it on, but again, when the bolts are so corroded, it's very easy to snap the surround.