Vintage Workshop
Services for Brough Superior motorcycles and their contemporaries

Valve spring trouble
last update 6/2003

When it comes to real engine bits, I try to use modern substitutes wherever possible. The problem with valve springs is that there are a lot available, but I do not know of any 3rd party supplier that would give their dimensions in a catalogue. If you know any thing of that sort, please tell me! So I had to resort to a set of re-made springs of unknown origin but correct dimensions. I should not have done that! Luckily, on explaining the valve stem lubrication to an interested by-stander, I noticed some disorder in the spring coils. Two of the springs were partly broken, but not quite. Thus damage was only to my pride, but not to the pistons!
So, off came the heads. Incidentally, I find an old cutlery drawer basket very useful to make sure all the bolts and rods go back to the same pot they came off!
I found the piston tops quite wet with oil. This made me decide to take the barrels off as well and fit the oil control rings I had left out when I had assembled the engine.
The rear piston looked perfect after 1200 miles...
... but the front one less so! I know the engine nipped up once during the first 10 miles I rode it, but I had not thought this would leave such a bad score on the piston. I cleaned he spot up with a very fine file and will see how things develop.
This is the spring of the rear inlet valve. I wonder when I would have run into serious trouble!
After taking the springs off, 2 of them collapsed to pieces.
To cut the story short, I fitted another set of these dubious springs, as I realised I will not easily find anything better. They will probably last for another 1000 miles, but I hope to have found a good substitute by then! So, back with the barrels (oil control rings fitted), anneal the head gaskets....
... and back on with the heads...
... and the gas works! Well, it runs now as fine as ever, but when I have found a modern car equivalent for the springs, I'll let you know! Re oil control rings: At the same oil feeding rate I do now have a much higher oil level in the crankcase (about 80cc if I drain it) but no bad leaks. So it should have been a good move!

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