Hi, y'all...
The engine for my basket case rebuild is a bit of a mongrel. I only had the bare, matching number, crankcase halves and the cylinder head from the original engine. The guy I bought the lot from had also bought a "donor" engine which I also acquired and I'm using the internals from that.
OK, first problem.. The donor engine had been used for racing and some of the bits were non-standard. I have a set of pushrods that aren't like any I've seen from suppliers like Andover Norton or RGM. They seem to be the correct length (8.25" and 7.40") but they've been machined from solid aluminium. Does anybody recognise them?
Second problem... Having re-assembled the cylinder head, the clearance adjustment screws in the rocker arms don't appear to be on the valve stem centre line. Mr Haynes says the spring washer should be at the innermost end of the rocker with the plain shim washer at the outer end, and that's the way I've assembled them. If I do it the other way round, I think the rockers will be too far the other way. I was thinking of machining up thicker steel spacers for each side or the rocker to align it with the valve. Am I overthinking it? Will it be ok as it is?
Thanks
John
Pushrods
Your push rods are an all alloy replacement version first sold in the 1970s. I do believe they were one of Wassells first Norton spares offerings and allegedly were made from Dural. While the main body was very tough, the cup ends were easily damaged especially when replacing the cylinder head.
It is premissable to use shims to help reposition the rocker feet over the valve ends. The racer boys quite often chucked the thrust springs and replaced them with shims/spacers in order to limit any sideways rocker movement.
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Its also possible that you…
Its also possible that you have a missmatch with the valve length and pushrod length . The Longer valves fitted to later 750 motors needed shorter pushrods , looks like you may be running the longer valves .
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Thanks for your replies
Alan ... Thanks. These do show signs of wear and I probably won't use them in the final assembly.
Phillip ... Thanks. I wasn't aware that these could have been a Wassel offering. Making up spacers to position the rockers is relatively easy. It's something I did way back in a different life as a "Rocker"!!
Robert ... As I mentioned, this engine is built from parts from different sources. The head was restored and the valves assembled by Seager Engineering, who I have great faith in. I refitted the rockers. I'm aware of the change in valve / pushrod lengths but won't really know what I've got until I put the whole lot together. I'll put it together with the alloy pushrods. See what it looks like and then assess whether I need the buy the longer or shorter new pushrods for the final assembly.
Peter ... That's possible, I suppose, but I think, unlikely, given the forces involved.
So.. I'll buy new pushrods. Whether they be the longer or shorter version has yet to be determined. I will probably reposition the rockers with custom spacers.
Thanks, John
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Be careful.
With regard to repositioning the rockers by making spacers, yes easy enough BUT I was always cautioned with this manoeuvrer that the racers did, as if the spacers grew due to temperature rise the rockers could lock up! Not a good idea. So one idea I saw was to make the spacers from phosphor bronze. But in the end make sure you have clearance and that such does not disappear when it gets hot! This was always the reason for the Thackery washers, good for mass production and cheap and cheerful.
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john, its ok to shim the…
john,
its ok to shim the rockers to centre them,you can use a bronze spacer or the thackery washers you have,,,the bronze bush and the shims are available from most suppliers,i,ve done that on my commando and dommi,if your concerned about expantion use the thackery washers and shims,
use the standard pushrods [alloy rods and metal ends],i would also use standard adjusters,all parts are available,
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Dural push rods
As Phil has detailed, the alloy pushrods were, indeed, supplied by Wassells. Their part number was (is) MD.32 G.
I tried a set in my 650SS in the early 1980's but found the cups wore out quickly (as my engine had low pressure lubrication to the rockers).
I still have another unopened pack.
I reverted back to the original pushrods and have not had a problem since.
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I had a set of these solid ally pushrods once. Rubbish, was the final decision on them. They managed to pick up some dirt in one rocker oiling hole, so the push rod then started to wear big time! Stick with the standard ones in this department.
Norton twin valve action geometry has never been good I also ask is it worth and successful to re-aline it?
The rocker screws, are socket head screws-good idea if they are hardened. Again I had a set that weren't hardened.