amal carb problem with mk 11 850

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hi all,
i think it's the first time i've used this forum
i feel defeated by the carbs on my very standard mk11 850 commando,
I am unable to reduce the idle speed below about 1500 rpm
i am reasonabley well aquainted with amals have done the obvious thing such as;
# stripped carbs
# needle position is the top groove (leanest)
# slide appears in good condition (perhaps wear is greater than i imagine and it's letting air past)
# ensured that the slides are free to drop to bottom of throat with correctly adjusted cable
# idle screws backed right off
# checked for manifold air leaks at head ,carby and balancing tube
# Actually sucked on the carby throat (hey whatever gets you off) and it appears to be a very small airflow past the slides (it's difficult to know what is correct)
# all airways and jets clear (air scews work as expected and engine runs best aith screw about 1 turn out)

Any help and suggestions would be greatly appreciated, it's so frustrating as i can't imagine where the air (and fuel) is coming from to enable the engine to rev so hard at idle, maybe it is just slide wear, i'm happy to buy new ones but would rather know it's the problem first
regards with thanks
al
 
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A good guide line when setting the slide to run is to use a 3/16 drill bit shoulder as a feeler gauge to set the idle adjustment screw. I use a pair of drill rods as tools to set the syncro of the pair at the same time. This will get you very close to the right idle speed. Once the drill stock is trapped under each slide (they only need to go in till they just touch the spray tube) and the slide is set so the rod will just slip fit in each carb just touch the throttle as light as you can watching the rods at eye level. Now you can set the cable slack on one or the other carbs to get them moving perfectly together. Once it's running you will need to set the idle just a bit higher keeping a good track on each adjustment so that it can be done to each carb just the same. I do this every time I set up Amals and have done hundreds of them. Be very fussy to keep the best accuracy with these adjustments and if you never checked the float height to see that they are correct and exactly the same you are wasting your time. If you have not set the timing with a strobe you are wasting your time.
 

Flo

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I have exactly the same problem, go out for a run, try to lower it & it speeds up again.
Contacted Mick Hemmings (via Angela) & the answer was "set it by the book". Mine is set with a colourtume, so I assume it is alright. In a few months I shall set it by the book & try it, as some work is about to be done on it.
Funny really, I only started riding with a tickover a year or two back, as I always cut the tickover off & just held the throttle when stationary. Only started using it because of the increase in traffic & hand signals. Considering putting winkers on & cutting the tickover again.
I can guess what somebody is going to say, don't do it.
 

Flo

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I havn't, will do as I am about to do a lot of work on the bike.
 
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The level of the fuel in the bowls must match and be correct this setting effects all the other adjustments and must be done as a matter of course as a base line first before you play at anything else.
 
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You said you have needle set at highest groove (leanest)
Leaning tends to raise rpm before falling off when taken too far.
Do the plug colors indicate running hot?
If so I'd try a lower notch to richen the mix that may drop rpm a bit.

Bo
 
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Flo said:
No, I've got a Boyer.

I had a lot of difficulty getting a smooth idle with my amals and boyer ignition. It all became a lot easier when I put a new, larger battery on and it now idles quite well. It might be worthwile to check the state of your battery and ignition box. That might be the main problem.
 

maylar

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Have you also poked the idle pilot jet clean? And those 2 tiny holes in the carb floor?
 

L.A.B.

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Can you tell if this high RPM running is actually occurring more on one side's carb & cylinder than it is on the other?
 
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