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O Biffa's Basement
Beginning a new thread
Sometimes things just have to be done, everything else in life has to take second place and something that’s been bugging you just has to be sorted. Such ideals came to the fore in The Basement recently and the CBG Triumph was on the receiving end of a bit of tlc.
Those who suffer this column on a regular basis, or saw me at Red Marley hill climb where I looked like James Dean in Giant – the bit where his oil well came in, not the iconic image of him with a rifle behind his neck – will know that the oil tank of my long suffering 650 Triumph gave up the ghost and spewed hot oil everywhere. I’ve used this as an excuse to leave the poor thing alone and plan a strip down and rebuild as there are several things that need attention.
With Biffa’s B40 having a few things away for specialist coating treatment, which means the kick-start will soon be shiny instead of rusty, it was an ideal opportunity to cast an eye over the Triumph. I was fairly certain that the oil tank had split, as there was so much oil everywhere and all the oil lines were still attached. As I could see nothing obvious I reckoned a seam had parted and was opening up as the tank got warm. Obviously this was going to involve welding then painting, so it made sense to get the welding bit done asap and the Triumph was rushed on to the workbench to strip out the offending part.
It turns out that the tank wasn’t split after all but the oil filter thread is so worn as to be almost non-existent and, under the heat of frantic competition, oil was getting past it. OK, the Triumph oil tank is a tin box with a feed through a gauze strainer device. This laughingly basic filter screws into the bottom of the oil tank and the engine feed screws onto it, which is all well and good when the bike is new and the threads are sharp. I’ve always been careful to use plumber’s thread tape – known as either ‘white tape’ or ‘PTFE’ tape – around the threads to seal them and this has been good enough for some time, years in fact. This is no longer the case and some repair work is going to be needed.
The accepted way to fettle up a bu… er knac… er stripped thread is to use a thread repair kit and as it happens one of these kits has just arrived in The Basement. Inside the kit is a drill, tap, some wire inserts and an insert tool for winding the things in. What happens is the old thread is drilled out, the tap in the kit cuts a new thread the exact size for the insert, which is then wound in and the thread is as good as new.
Not wanting to experiment on a bike part, I got a bit of scrap alloy, drilled a hole in it, forced a bolt through until it destroyed the thread and set to with the repair kit. First up was a quick glance through the instructions to see what to do. They were surprisingly easy to follow and did have the warning ‘keep the drill and tap square to the work’ for best results. I did this by setting up my pillar drill and drilling out the thread then fitting the tap and turning it by hand – it was unplugged at the time! It was a simple task then to fit the insert with the tool, break off the tang and screw in a new bolt of the correct thread. Wow, was I impressed.
It’s at times like this you want a large and appreciative audience but I had to make do with next door’s Jack Russell peering through the fence. Anyway, thanks to Will at Trafalgar Tools I can now repair 1/4in BSF threads – primary case size for BSA B40s if you were wondering. But they’re a bit small for the inch-and-a-bit diameter that the oil tank needs. So, what will be done to this thread will involve a bit of machining to turn up a ring, have it brazed in place, a thread cut in it to take a new filter, maybe with an ‘O’ ring on it and then I can slap some paint on, secure in the knowledge that I’ve finally cured one more oil leak on my Triumph.
Tim
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