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1 Posts

Posted - 09/19/2011 :  13:28:09  Show Profile  Visit Drubi's Homepage  Reply with Quote
Good evening,

Last year a bought a set of brandnew Amal 932 carbs and it was only last week that I was thinking that I couldn't carry on like that (won't hold idle speed and rpm "floats" sometimes around 1500rpm rather than returning to idle) so I decided to replace them thinking to myself "it isn't rocket science, how hard can it be?" but I guess I was way off...

I've read some older (2006) posts of JubeePrince about the pilot jet of Amals that more or less correspond to what I have now; my Norton 850 MK1a is difficult to start and she only runs idle on the left cilinder. When reving up above 1500rpm, the right cilinder kicks in at sudden. When closing the gas the opposite happens; just under 1500rpm the right cilinder stops and only idles on the left.

I've opened the right carb several times, blowed it through, cleaned it and.. No difference, same thing happens.

I may have found (in theory) the answer; when I bought the new Amals I only checked the main jet size (230) and didn't pay attention to anything else. But as it appears, the needle (4 rings for a Norton) and spray tube are different, too?!?
I've opened and checked the old carburator, those pieces are exactly as the specs for Norton indicate, while the new ones ... don't correspond at all.
I know, perhaps a silly question, but if the inner configuration of the Amal is wrong, could that lead to the result I have?

f scott dundas

253 Posts

Posted - 09/22/2011 :  18:20:20  Show Profile  Reply with Quote
The main area of wear and hence erratic running at idle speed will be the slide and bore of the carb body. The jets will probably be OK in the original carbs. Try replacing the jets in the new carbs with the old. Im assuming the slides in the new carbs are the correct cutaway. Also check the timing and make sure you dont have an intermittent short or fuel blockage.
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