Idle Problem Fixed

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Jul 19, 2003
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I've posted a few times before on a hot idle issue that I had on my 73 850. After getting some excellent advice on setting up the Amals mechanically and replacing my throttle cables, I went out for a ride today. The problem is fixed, I've got it set up so that it idles around 800. If I blip the throttle, the idle drops to around 600, then slowly returns to 800. After I get back from my next ride I'll probably tweak it a little more, but the settings are at the point that when I adjust the trottle stop screws I'm only taking them less than 1/8 turn. I think it's pretty close now.

Some observations...

1) On this bike, using a 1/4" drill bit to set the throttle slide height with the throttle stop screws gets it very close to the best setting.

2) I know that the nominal setting for the pilot jet screw is 1.5 turns from full in, but on these carbs, the best setting is around 3/4 of a turn from full in. I set it up at 1.5 and the bike fired right up on the first kick, but then started spitting back through the carbs. I took them in to 1 turn from stop and the spitting back stopped, then I went for a ride and came back when the bike was warmed up and found that 3/4 turn seems the best. I guess this is okay because the bike idles best at this setting - does anyone else have their carbs set like this?

3) The float heights are identical. Both of them were low when I started this exercise, with the right carb being very low. So, prior to this tuning the bike was running a little lean which probably contributed to my hot stalling.

4) The pilot jets are clear. The left was okay, the right might have had some minor obstruction.

5) So far, the most frustrating thing I've done on the bike is to take the stock air filter out of the stock air box. It used to be nearly impossible when I had a K&N filter in it, now it's just merely incredibly frustrating. Does anyone have any tips on how to do this EASILY?

The next step will be to balance the carbs with a Morgan Carbtune.

I appreciate all the help I received on this forum, it helped me fix a problem and also taught me about setting up Amals.
Don't worry mate you're doing fine, as long as the air screw isn't too far in or out and she runs well. 3/4 turn only indicates you might be getting a little more air leaking past the slide, or you may be well setting the screws with the tickover too low.
I don't like idling that low, it's lugging the engine.

The low speed mixture screws should not necessarily be set the same, or at any specifit number of turns, etc. they SHOULD be set for proper low speed mixture, which could end up being anything, depending of the condition of the mixture screw tip and the seat in the carb. Also, a lot depends on the particular setup you might have. I've had some carbs more than a full turn difference from right side to left side.

The "1-1/2 turns out" setting is a general baseline STARTING point from which you tune the bike to obtain the best setting for your conditions.
Thanks. Yeah, there is a slight difference in the mixture settings between each carb. What tickover speed to you set your bikes to? Mine seems real happy at 800, but there are times when it drops below that. I may set it a little higher after the next ride.
Given that the rev counter could be miles out, about 900 to 950. Mainly because I have a very bad right knee and hip and cannot afford to stall the beggar.
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