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Amal Premier report

Classic Norton Commando Motorcycles.

Amal Premier report

Postby mgrant » Thu Jul 05, 2012 7:20 pm

After a full mechanical rebuild and installing a Sparx 3 Phase and a Tri-Spark, my bike ran great except a few little issues that seemed clearly related to the standard Amal carbs.
    1. Even with stay-up float kits installed, the float on the right carb would consistently hang up and piss gas when I released the tickler.
    2. Very randomly the bike would idle at 500 rpm instead of 800, and when I cracked the throttle open when it was idling at 500, it would always give a lean spit back through one of the carbs. When it would idle at 800, there was never a lean spit back.
    3. I was not able to sync the carbs with my Morgan Carbtune manometer. The left carb responded normally, but the right carb didn't. The metal slider in the manometer tube didn't bounce at all like the left carb and it wouldn't move much with carb adjustments.
    4. Frequently when I would close the throttle and roll up to a stop, the bike would idle between 1200 and 1400, then slowly drop down to the stable idle speed.

I like the looks of the stock carbs and airbox so I decided to try the Amal Premiers. From the outside they're just a stock Amal, but the finish is a slightly brighter silver. Looking into the throat you can see the dark anodized slide. With the old Amals, the jetting seemed to be about right, excellent response from idle to redline, no flat spots in the power and no misses or pops. The plugs looked okay, sooty around the base, but the electrode and tip are a nice medium gray, and the mileage was pretty consistent at around 42mpg while I was breaking in the engine and constantly varying the throttle. So I ordered the Premiers with the same jetting as the older carbs, which I think is stock for an 850; 106 needle, 260 main jet, 3.5 slide, and the idle mixture jet at whatever is standard.

All of the above listed problems were solved by the Premiers. I found it very easy to tune the carbs with the manometer. I was able to sync the slide height for idle and sync the slide lift off in less than 10 minutes without removing the tank, and I did notice a slight difference in smoothness and responsiveness. The shop that installed the carbs for me doesn't use gauges and they got the settings pretty close, but the minor tweaks that I did made a difference. Now, it will be really easy to make sure that my carbs are synced.

Looking back, the old right carb probably had an air leak that was causing the lean spit back and random idle fluctuations, and it could be what made the carb hard to tune with the manometer. Whatever the cause, the problems are gone now. So far, I'm very satisfied with the Premiers. I'll see how they perform after a few thousand miles.

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Re: Amal Premier report

Postby Whitworth Ranch » Thu Jul 05, 2012 7:32 pm

This is about the same experience I've had with my Premiers. I've probably run them about 1000 miles. With these and a Tri-Spark, idle is rock-solid and the carbs tune like instruments. I also set idle and throttle pickup (cable length) with a manometer and have to say it makes a big difference in smoothness and response. My sleeved Amals never ran like this. Steady-state freeway cruising at 75-80 mph with a 24-tooth front sprocket has returned about 55 mpg and my last tank of mixed town/highway, now running a 23 for increased pep, was 50.

I had to use richer #3 slides (California gas, I think), but the rest is as you describe. It runs beautifully and I am not tempted to try anything else at the moment. I'll be interested in longevity, like how slide-to-body wear is over the next 5000-8000 miles.


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Re: Amal Premier report

Postby AussieCombat » Thu Jul 05, 2012 7:47 pm

Thanks for sharing guys,
that has to be a good result for those wanting to stay original.
24 teeth, wow, I use 22 and thought that was high.
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Re: Amal Premier report

Postby Whitworth Ranch » Thu Jul 05, 2012 9:34 pm

Yes, 24 was a bit too much. I'm pretty happy with 23. It is pretty smooth at 60 and the gearing for "natural" speeds in street riding seems pretty good. It was definitely much snappier with the 21, but cruise at 75 is much more relaxed now, and there is plenty of 75 mph needed in Southern California. A 22 might be the next step. Dunno. I am pretty sure I don't want to take off the primary again for a while, though. I've been in there three times recently with various things. Just going to roll with it for a while.

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Re: Amal Premier report

Postby concours » Fri Jul 06, 2012 3:30 am

22T yeilds me 4000 rpm at 80 mph indicated, JFWIW. I'm a big fan of long legs, and I'm very happy with 22.
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Re: Amal Premier report

Postby lrutt » Fri Jul 06, 2012 4:43 am

Tempting. I just dropped the new slides in my old carbs and they ran so much better I thought I was very happy with that. Maybe later after the stockers wear a little more I might try the premiers.
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Re: Amal Premier report

Postby madass140 » Fri Jul 06, 2012 5:04 am

that sounds promising, I have a set of premier's on my 98% unfinished 750 Interstate, not started yet, but I'm confident that I made the right decision. I reckon once there is a few good reports , they will be a big seller.
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Re: Amal Premier report

Postby shrugger » Fri Jul 06, 2012 11:32 pm

for those of us with 72 Combats. Typo?
AMAL has listed as 1973 Combat for the Premier's ?!?
72 Combat Roadster
70 T120R Bonneville
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