The 650 Norton thread

Fast Eddie

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annajeannette... you are replying to comments posted in 2012... by a member not seen on the forum since 2015...
 

t ingermanson

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I'm going to risk some ire, and breathe a bit of air into this one.

While researching the difference between a 650ss and Mercury, I'm not getting very consistent performance info. Seeing a variation in bhp, from a claimed 47 to 52 (most claiming 49 for the 650ss). With the single carb on the Mercury, I would expect lower performance values, but not sure how much.

Does anyone know if the Mercury was detuned more than just the subtraction of a carb? Still running the SS cam? Same 9:1 pistons? I read that it may have been "tuned for unleaded fuel", but what does that really mean? Given the reputed state of Norton at that time, I can't imagine there was much done engine-wise for the inventory-clearing exercise that the Mercury seems to have been.

Somewhere THE INTERNET claims the Mercury was more of a "touring" bike, and I understand the lower compression Atlas was marketed as such, but can't find any actual information that points to a touring intention of the Mercury other than a single carb. Is that all it took to make a "touring bike" out of what was marketed as the top road scorcher the year before?

I understand the 650ss changed over to larger concentric carbs late in its run, and therefore the Mercury too? Is there a measured power loss? Many say their Dommie "runs better/stronger/faster/louder with monoblocs", but what's the data, if any?

Does anyone have any Norton literature or period magazine testing that differentiates the two models more? I'm mostly concerned with motor differences, not the tinware.

Thanks.
 
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Most likely that the Mercury was a stopgap to use up the remaining feartherbed stocks. Why touring Trim?, a likely explanation is that they did not have/could not afford the Expensive deep valenced chrome guards so reverted to the cheap light painted guards and painted case ,a single carb fits well with that image. Can't imagine that they would have commissioned a batch of LC pistons just for that. Even if there is somewhere an "Official" explanation I would take it with a pinch of salt as they were past masters in propaganda.
 

t ingermanson

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Most likely that the Mercury was a stopgap to use up the remaining feartherbed stocks. Why touring Trim?, a likely explanation is that they did not have/could not afford the Expensive deep valenced chrome guards so reverted to the cheap light painted guards and painted case ,a single carb fits well with that image. Can't imagine that they would have commissioned a batch of LC pistons just for that. Even if there is somewhere an "Official" explanation I would take it with a pinch of salt as they were past masters in propaganda.


Yes. Exactly, and why I would like to figure out what was actually inside one of these motors from the factory and what I should expect to see when opening one up.

The info on the 650ss seems pretty exhaustive, but not much is out there when it comes to the Mercury.
 
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I'm pretty much in agreement with NB.
The 650 components readily available to assemble this slimline should be fairly straight forward.
There are several examples of 06-0380 head cores originally intended for commando, as being finish machined as small bolt pattern, small combustion chamber, no spigot counterbore, and featherbed top of head oiler, regular 1.4" intake valves instead of 750/1.5" .
SS cam like ALL NHT of that period(61-70). crank, rods, cases (finished for small bolt pattern barrels) only difference is the flywheel.
All you need to do is reintroduce the 1x2 intake manifold from the early atlas.
Turn it over to the marketing department and bingo, one carb touring bike.....LOL
 
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t ingermanson

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I'm pretty much in agreement with NB.
The 650 components readily available to assemble this slimline should be fairly straight forward.
There are several examples of 06-0380 head cores originally intended for commando, as being finish machined as small bolt pattern, small combustion chamber, no spigot counterbore, and featherbed top of head oiler, regular 1.4" intake valves instead of 750/1.5" .
SS cam like ALL NHT of that period(61-70). crank, rods, cases (finished for small bolt pattern barrels) only difference is the flywheel.
All you need to do is reintroduce the 1x2 intake manifold from the early atlas.
Turn it over to the marketing department and bingo, touring bike.....LOL


That sounds great, what was expected, and what I was hoping for. Just picked up a late Mercury motor, so it'll be interesting to see what's inside as opposed to the 67 650ss motor I've got. I realize they were all built at once according to lore, but the number is late in the run, so it may have something interesting going on. Or perhaps not any more interesting than any late 650ss.
 
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John Hudson ,Norton factory guru and the most practical Norton owner ever ,ran a Mercury to the end and thought very highly of it.
 
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