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OK to weld fins back on Barrel

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

OK to weld fins back on Barrel

Postby Granty » Sun Jun 14, 2020 8:27 am

Guys -- I've got an original 150 barrel, it's been butchered when trying to get the seized piston out and lost a few fins. I have the bits, has anyone just welded the fins back on as well as the usual re-bore etc? Just wondering if this is a lost cause? Have a good day all -- G
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Re: OK to weld fins back on Barrel

Postby holty » Sun Jun 14, 2020 10:08 am

welding cast iron is not very easy, I know you can buy cast rods for using in a stick welder, only other thing I have seen done to cast iron is braizing, but you will need an oxy acetyline welding plant, is it worth doing, depends how many fins you have lost and what is the barrel worth.
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Re: OK to weld fins back on Barrel

Postby Warkton Tornado No.1 » Sun Jun 14, 2020 11:31 am

Brazing them back on as Holty suggests is a good solution & worth doing IMHO. It will aid cooling, but so does cleaning the barrels back to parent metal, which you ought to do prior to brazing.it'll probably take longer to get the jigsaw pieces properly positioned in place than to braze, but will tell on how the finished job turns out.

(If the bore is tatered, you could always braze in a piece of fin to bridge the exhaust port for an old school tune, prior to boring. Nowt wrong with a nice wide exhaust port if bridged, & in my experience, can be extremely torquey)

There are Eutectic rods available for welding, but I'd still opt for brazing with oxy-acetylene. BTW. Don't be tempted by claims that a blow lamp will ever get hot enough..... :roll:
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Re: OK to weld fins back on Barrel

Postby Granty » Sun Jun 14, 2020 1:40 pm

holty wrote:welding cast iron is not very easy, I know you can buy cast rods for using in a stick welder, only other thing I have seen done to cast iron is braizing, but you will need an oxy acetyline welding plant, is it worth doing, depends how many fins you have lost and what is the barrel worth.



Thanks Guys -- lost 3 or 4 fins so far, going to a machine shop to hydraulic press out the piston the last inch or so -- might not be worth it in the end as you say but wanted to keep the original barrel if I could. Cheers G
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Re: OK to weld fins back on Barrel

Postby Wack » Fri Jun 19, 2020 10:50 pm

I just MIG them back on,not had a problem.
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Re: OK to weld fins back on Barrel

Postby Brash » Sat Jun 20, 2020 9:18 pm

I use a small oxy-turbo set which is basically like a gas welding torch (3000*c) and brazing rods with a high percentage silver which make them run at a lower heat. Also best to get the barrel aqua blasted or similar for best results.
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