- 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.