MAKING TWIN TANKS
I’ve been making twin tank conversions for what seems like a life time, when Dean Orton of Rimini Lambretta sent a tank and tool box for doing a conversion it made me think.
It was 1986 when I first did one, I remember it well, it was for a Liquid Cooled 230 bike I did for Steve Ash in Southampton, and he still has it. I’ve rebuilt his bike a couple of times when he’s wrote it off. Surprisingly it wasn’t when he caught the train to collect it the first time and on his first road test my dog chased him into the gutter! Opps!
Originally this bike was a cast LC cylinder, now it’s a TS1 230, the frame is Liquid Cooled with frame mod’s and it’s …………………….. a genuine SX200!
As part payment when it was restored to white restoration he paid me with a UK GP Electronic and a Tv200! I kept the GP, it’s the Carbon one on our Lambretta Spares home page and I sold the Tv to Rob Skipsey. There’s always a story to tell, runs in the family.
So his was the first, and it started from there, except the first one I sealed the tank and toolbox separately and used an extra petrol tap from the toolbox and a had a cut out in the panel to get to the tap and yes it was a genuine Sx200 panel as well but it did show off the 4 petal reed valve and water cooled barrel as well.
The filler cap was under the toolbox and it was all a bit of a pain to use. I looked and thought I can connect the tank and toolbox together by pipes and use one the original filler cap and petrol tap. So with some tweaking I redesigned it with a large lower pipe to fill up quick on a refill but for this to happen it would need a bleed pipe at the top. This way it would hold as much fuel as possible.
Others in the Far East have copied my design but used a little pipe at the bottom and it took days to fill up……….. NEVER BUY INFERIOR PARTS!
All that needs thinking about is where the pipes go to clear either the carb on either side, the battery or air box.
Now all this sounds easy but trust me its not. Metal thickness varies as does quality from manufacturers, condition and rust effects the job so everything needs to be perfect and supplied with paint stripped and sand blasted to help me do the job. Some Indian tanks are badly twisted but can be tweaked to fit. Small dints usually come out before the job is finished so this isn’t a worry, but any tank with rot is a waste of time working on. Nearly all have shit under the metal seems and this can be a right pain to weld over or remove and the smallest of hole that you can not see WILL LEAK when tested!
When the tanks are finished, reblasted, painted and fitted to a bike you will see they look standard. My usual approach to doing conversions to Lambrettas so they are wolves in sheeps clothing. Always tidy, neat and functional.
If you follow the photos you can see my step by step way I go about making the MB Twin Tank.
Take a perfect tank and sand blast it
Measure the strange shape and cut out some sheet metal
Roll bend and shape it to fit this strange shape
Tack the plate into position, taking care to get it to fit
The plate has to be sealed
The mounts for the tie rods have to be welded to seal the spot welds
Then all the seems need welding to totally seal the tank
Mark Broadhurst any questions ask email@example.com