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Kind of the same, kind of different

Discussion in 'Modifications and Projects' started by mattb, Mar 23, 2009.

  1. Hey All.

    I'm going for eccentric question of the month.

    I'm not a big fan of the angles on the tank and side cover of the Starfire, but anyway not to digress...Here is a picture of the BSA Starfire


    And here is another


    Have you opened up both and had a good look? I once shared the second picture and somebody referred to it as "that blue abortion". I don't know what went on, but in my book as long as you don't cut the sacred brit iron then all is ok. And besides, it's a damn fine engine, that SR500 engine you can see there.

    I contrasted these engines to communicate a sense of a long-term niggle of mine. While they build the best engines, aside from the XS650 and direct imitations like the W650 the Japanese don't build beautiful engines. Not compared to some of the works of art that came out of the West prior to 1970. Now, I frequently see right side engine covers going on eBay for not much (who needs a right side engine cover?! - SRs are too slow to crash!), and I gets to thinking: could some light metal be moulded onto a spare engine cover to create that egg shape, or at least some nice rounded-ness, that made the earlier engines such a work of art, covering especially that busy front half of the cover? Of course that creates complications: for instance what about heat dispersal? How much of an issue is it? Would a series of spilt pipes, open-ended and drawing air across the original surface, be enough? What sort of metal would be used? I think I can get round the access to teh oil filter issue. Do other people have ideas how to do this of it is do-able?

  2. As per usual, I've got some ideas on this. No time to expand on them now but will get back to you later.
  3. IIRC, the SR's a dry sump design with the oil in the frame. If that's the case, I wouldn't regard heat dispersal as being a huge issue as the engine isn't (or shouldn't be) relying on long residence times in the ally crankcase to cool it. I wouldn't expect any problems from covering up the case. Certainly none that couldn't be cured by the addition of a small oil cooler, probably in the return line.

    How much "stuff" lives inside the case?. I assume the clutch, but what else? Perhaps more importantly, how much stuff requires the cover for support or location?

    if the answer to the last question was nothing, it opens up your options quite a bit. My thinking in such a case would be to get a spare cover and build (or, at least, have a competent ally welder build) the desired egg shape on the outside, fabricating a skeleton from sheet/plate and building up enough thickness that the result can be carved to the final profile. Having done so, and, hopefully, being confident in the welder's ability, I'd consider cutting away the now reduntant areas of the cover to allow the oil to get a bit closer to the outside world.

    Of course, this would also work without cutting away the cover, allowing the technique to be used even if various bits rely on it for support but I have views on adding stuff to motorcycles that doesn't work for its keep :grin: .

    Welding on the cover is highly likely to cause some distortion so it won't seal flat any more. Any machine shop or competent amateur worthy of milling machine ownership should be able to correct any problems by taking the lightest of light skims over the mating face.

    I can't think of too many other materials that could be used to mould the required shape. Various epoxy fillers could probably be used, but you'd have to paint them and they would probably be working at the upper end of their useful temperature range. On the plus side, epoxy and microballoons would almost certainly be the lightest solution.

    Nope, I'd still go with the ally fabrication. Thinking about it, it's surprisingly easy to beat aluminium into a suitable shape if you're not worried about achieving a brilliant finish right off the bat but are prepared to go at the final product with files and sandpaper to get rid of the hammer marks. Maybe go with a strip of ally bent around the perimeter, with a beaten to shape outer casing welded to it and blended in.

    Of course, if you really want to go the whole hog, you could try finding one of these guys in your area and seeing if it would be possible to cast a whole new cover :shock: and get it machined.

    Realistically, though, you're going to be limited to fabrication and carving. Not a quick and easy job by any means.
  4. Thanks Pat! This would be the last of my priorities but when all the other stuff's done I'm pretty sure it's going to be on the books (half the fun of this bike is modding it). I think the idea of having an allow frame built up and then covering it is best. The SR is oil in frame, and a cooler is definitely on the books.

    My partner's uncle, a very technically clever man, is a fanatic for machines - very early Melbourne-made tractors for instance, with red-lines at 600rpm, lined up in his suburban backyard, and he collects any crappy little engine that comes along and repairs it for fun. And...he has all the metal-work machines!! Plus, while never a rider, he likes bikes.
    Methinks I need to get cosy with this guy! Maybe go mow his lawn for him (with one of the array of old lawn-mowers he has found and repaired).