Idle dont goes under 2000 mph

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pierodn

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Hi.
Is a 750 with amal 932, cut 3 throttle valve, 220 main jet, 106 needle jet, throttle needle with jet needle clip in the midle notch.
But the manifolds are 930 in and 930 out.
When the engine is hot the idle dont goes under 1900/2000 mph.
The bike runs very very well.
What i have to do?
I dont want to change the carbs.
Thank you.
Piero
 
Surely this has to be because the throttle slides are not closing properly? Sticking slides, or short cables ?
 
Or, an air leak at the carb-manifold or manifold-head joint, or a split balance tube?
 
Hi pierodn.
Assure that the slides close completely against the upward angled throttle speed screw on the outside of each carburetor. With the engine not running, open, then snap the twist grip shut. You should hear a 'clunk' as the slides quickly drop onto the throttle speed screws. If you do not, either the slides are sticking in the carburetor bodies or the throttle cables need to be adjusted longer. If you do hear the clunk, equally turn those screws out a little at a time until a slower idle speed is achieved.
 
Hi, it's my roadster...
thanks Piero :)
yes we first checked throttle cables and we found the throttle slides work fine,
so it could be an air leaking problem from the manifold...

I believe manifolds are a bit "irregular" I mean not perfectly flat...
I will work on them to flatten both surfaces and check for some hidden crack,
do you use any sealant between head and manifold and between manifold and carbs?

thanks in advance
Mario
 
If you have AAU and points the AAU may not be retarding sufficiently to lower the idle.
All the best.
 
If the AMAL carburetors were not originally used on the Norton Commando, it's possible that the carburetors are bumping into each other and preventing them from seating properly on the manifolds. If the carburetors are rubbing against each other you need to file some of the material from the carburetor bodies so that they don't touch each other.

Peter Joe
 
Check for manifold leaks by spraying some WD 40 around suspect areas and watch for smoke in the exhaust.

Slick
 
AntrimMan said:
If you have AAU and points the AAU may not be retarding sufficiently to lower the idle.
All the best.
Click to expand...

+1 what he says.

The Automatic Advance Unit (AAU) is notorious for stick the ignition in the full advance. This is the most typical cause for a high idle. See if you can confirm the AAU is free to move and spray a little lubricant in there......assuming you still have points.
 
Dances with Shrapnel said:
AntrimMan said:
If you have AAU and points the AAU may not be retarding sufficiently to lower the idle.
All the best.
Click to expand...

+1 what he says.

The Automatic Advance Unit (AAU) is notorious for stick the ignition in the full advance. This is the most typical cause for a high idle. See if you can confirm the AAU is free to move and spray a little lubricant in there......assuming you still have points.
Click to expand...

Had the same problem. Kept cleaning the single Mikuni, checking the cable and route, lubed the AAU. Still had the problem. Replaced ignition with a Tri-Spark and single coil conversion, BINGO! Immediately idled nice and idle came back down as it should while riding without having to blip it.
Idle dont goes under 2000 mph

Idle dont goes under 2000 mph
 
Dances with Shrapnel said:
AntrimMan said:
If you have AAU and points the AAU may not be retarding sufficiently to lower the idle.
All the best.
Click to expand...

+1 what he says.

The Automatic Advance Unit (AAU) is notorious for stick the ignition in the full advance. This is the most typical cause for a high idle. See if you can confirm the AAU is free to move and spray a little lubricant in there......assuming you still have points.
Click to expand...

Hi,
I don't have points,
I have a Boyer Bransden e-ignition fitted on the bike,

since the bike was just rebuild I had kick back problems,
It was a bit advanced,
working on the ignition plate and using a strobo the problem has been solved,
but, yesterday the bike was again a bit advanced and gave me some kick back,

Idle still too high 2.000 rpm since the bike was rebuild, no way to lower it,

Do you think it could possibile I have a problem with the e ignition?
May be it doesn't work correctly?
I could try to fit another e ignition...
Thanks
Mario
 
Did you by chance just clean and perhaps oil the air cleaner filters as this will often produce a fast idle if they are to heavily oiled!
Regards Mike
 
Hi mario/piero.
I had a similar problem when a throttle slide skirt broke off and the gap created a lean condition and fast idle.
Ta.
Just curious: Is the head 30mm to match the manifold? or 32mm like the carbys but with 30mm manifolds?
 
needing said:
Hi mario/piero.
I had a similar problem when a throttle slide skirt broke off and the gap created a lean condition and fast idle.
Ta.
Just curious: Is the head 30mm to match the manifold? or 32mm like the carbys but with 30mm manifolds?
Click to expand...

Hi needing,

the head has 30 mm port with manifold 30/30 mm
carbs are 932 from a 74 mk2 850 but with the standard 930 setting:
220 main jeet - 106 needle jet - slides cut 3

(the original setting was 260-106-cut 3,5)
 
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