Is the gearing correct?
Hi Jonathan,
While the issue may well be carb related (sounds like it is running weak), are you sure that the gearing is correct?
There is every chance it has been raised over the last 60 years and the engine simply can't pull it?
Regards,
George.
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I can't believe that too…
I can't believe that too large carb size will big it down at high revs. Might make it less flexible low down. You have lifted the air slides? The correct size was 1 1/16 monoblocs, but mine runs fine on a pair of 28 concentric
I'd check air leaks in manifold, air slides properly lifted, both carbs are opening together, and of course timing. Fuel tap filter blocked, fuel hose blocked. Needles sound high, but there's no standard to go by so you need to go through the Amal setting up list.
And is the camshaft OK? A rough check might be possible by looking at the movement of the tops of the push rods.
If it was over geared it should get to max in 3rd gear instead of top.
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There may be other issues with this bike but my gut feeling says the carb is way to big and wrongly jetterd for this Norton. The original Carb was a 1 /1/16" Monobloc with a 250 main jet. With two of these on the 88SS. Twin 626 or a single 928 Concentric would possibly be better. I would also suggest 240 main jets and do plug chop checks to get the mixture correct.