They had a bad rep for big ends not lasting long after a rebuild.
That's because they have a hollow galley in the cranks throws that act as a centrifugal oil filter, which wasn't widely known about.
These need cleaning out every so often due to a build up of sludge, which can build up till it is half full with hard sludge and block off the oil holes to the BE bearing.
A wire can be pushed in which will feel like it's clear but it ain't, the screwed in end caps need removing to clear the galleries out.
No I don't think it can be, memory is a tad hazy..
Anyone watch "Junk and disorderly" on the box tonight ? That double engined sunbeam was being ridden around an autojumble by Sam Lovegrove. Very long looking thing. Sad to see the British Motorcycle Museum in west London is closing down and selling off their exhibits.
After welding up the sump plug hole it warped the casting in the corner for about 3" requiring attention; if I ever wanted it to be oil tight. Just a dry fit at the moment, oil strainer cage needs dropping, oil pickup needs lengthening.
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While the sump was off, I could see the bores, and unfortunately it looked like they were scored.
The head needs to come off to replace the leaking composite gasket, so that was the next job.
Rocker cover is also warped so that got a rub down. It also doesnt lineup with the head, as the holes are out of alinement, they arent flat either. So Ill weld them up and mill new holes in the correct place
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Cam looks in good nick, rocker faces are fine, valve caps need replacing.
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The head is held down with 11 bolts, two of which are behind the camchain cover.
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Good old British engineering
Head came off very easily, a bit of coking
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A shiney bit of sheet to make a new gasket
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You going to have it rebored ? Are the cylinders separate to the crankcase or are they all one piece like modern bikes ?
Would you not save yourself the hassle and order a gasket off Draganfly or whoever sells Sunbeam bits
That cost me £9.79. To buy one is £69. Took me 30mins
Besides no pain, no gain