New Amal 932 carb adjusting

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I set my pilot mixture screws perfectly with two Colortunes.

Then I had to change their settings, to get it right!
That's not surprising to me...

I get tired of explaining why it's important to understand that the best static A/F ratio at idle, set by the idle air screw position is not necessarily the best placement for the idle air screw because it ignores the screw position's effect on early throttle engagement, which is a dynamic interaction, so the screw position has to be set with a dynamic method that explores the screw position's effect as the secondary fuel component combines with the idle air screw setting as the throttle is engaged.

If you can do this with a colortune, I don't see a problem, but plenty of people complain about how their bike idles fine, but has a stumble when they accelerate. Their problem, I have found in some cases, is they don't set their idle air screw position dynamically.
 
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A tool is never a substitute for knowledge - it can' think. So to blindly set a colortune and say "I nailed it" if your bike runs like garbage is just as silly as saying it has no use because I can sniff the exhaust and get to the one hundreth decimal place on the A/F mixture, which while I've never technically heard that, some are not far from it as times. The goal is to have a reliable, rideable bike that I enjoy. If folks have a similar goal may they get there how they like but don't lose sight of your own end game and using tools doesn't make you less educated. I have a 74 Trident T150V which is why I bought mine and it certainly helps when you have the old "middle" carb thrown in to the fun.
 
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maylar

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A Colortune can also tell you if something's wrong. If you can't get the right flame color with reasonable movement of the air screw something's wrong. This is especially true when using digital EI with idle stabilization. My TriSpark ignition will hold the idle speed steady over a wide range of AF adjustments. Tuning by ear is nearly impossible.
 
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A Colortune can also tell you if something's wrong. If you can't get the right flame color with reasonable movement of the air screw something's wrong. This is especially true when using digital EI with idle stabilization. My TriSpark ignition will hold the idle speed steady over a wide range of AF adjustments. Tuning by ear is nearly impossible.
Exactly why mine was pulled out of the cobwebs, idle stabilisation curve was messing up the manual tuning routine.
 
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A Colortune can also tell you if something's wrong. If you can't get the right flame color with reasonable movement of the air screw something's wrong. This is especially true when using digital EI with idle stabilization. My TriSpark ignition will hold the idle speed steady over a wide range of AF adjustments. Tuning by ear is nearly impossible.
the idle is steady anyway over a wide range of A/F adjustment at an idle only... It's only when the A/F ratio gets nearer to it's rich or lean stumbling points at an idle that it breaks up.... My amals have almost 3/4 of a turn of the screw where it will idle fine, but a very narrow range where it accelerates smoothly...

If you don't lift and lower your throttle observing how smoothly the idle air screw position interacts with the secondary influence of lifting the throttle, then you set Your idle air screw "statically", which ignores the idle air screws participation in the lower RPM range's A/F ratio...

Again,... If you can use the colortune in this process, then it's valuable. If it only works for static A/F adjusting, then you are using a gadget instead of your brain.

The most important thing is understanding how the idle circuit and the secondary fuel delivery components interact, so you can understand WHY just statically positioning the idle air screw ignores a big part of it's function in the low RPM range.
 

maylar

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If you don't lift and lower your throttle observing how smoothly the idle air screw position interacts with the secondary influence of lifting the throttle, then you set Your idle air screw "statically", which ignores the idle air screws participation in the lower RPM range's A/F ratio...
I never said that a Colortune is the be all end all of AF adjustment. I said it's a useful tool for verifying that your carbs are working within their design parameters at idle. If you can't get the blue flame within 1/2 turn either side of 1-1/2 turns out, something is wrong.

On a sample of one, my own bike which I've been tuning for 45 years, I've experienced the off idle stumble that you mention and found that slowly enrichening the mixture from the perceived "ideal" point makes it go away. It ain't rocket science.
 
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I never said that a Colortune is the be all end all of AF adjustment. I said it's a useful tool for verifying that your carbs are working within their design parameters at idle. If you can't get the blue flame within 1/2 turn either side of 1-1/2 turns out, something is wrong.

On a sample of one, my own bike which I've been tuning for 45 years, I've experienced the off idle stumble that you mention and found that slowly enrichening the mixture from the perceived "ideal" point makes it go away. It ain't rocket science.
Well Dave, I'm just trying to popularize the idea of setting the idle air screw position with a certain technique because I see people complaining that their bike idles fine, but stumbles when they take off... What they lack is the understanding of WHY it stumbles, and of course that precludes them from knowing HOW to fix it...

The "it ain't rocket science" comment implies that it's a simple thing that pretty much everyone already understands. I pretty much explained it 5 times, precisely because I don't think all that many people understand the complete interaction of the idle screw setting... beyond just setting the static A/F.... Done


,
 
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I set my pilot mixture screws perfectly with two Colortunes.
Then I had to change their settings, to get it right!
What you are saying here is that after getting the A/F ratio 100% correct, ( or so you say,- no offence ) then it went onto the next carb circuit and stumbled. ( please read my next post) All carbs have overlapping circuits, but they also need to be set up correctly in order for smooth acceleration, just look up one of the many Amal carb pages for an explanation.
You set both your pilot screws perfectly, but you neglected to jet the next circuit set correctly for a smooth transition. Setting carbs is not all plain sailing it's a lot harder than that, even one cylinder firing in a different timescale on a twin- and there's a few like that with a out of kilter K2F magneto- will have an adverse outcome to smooth engine running.
 
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Colortune does the idle plus if you look at it as you just open the throttle you can see if the slide cutaway is correct or not. Fudging the idle so you get a clean throttle opening off the throttle stop works for a short time, but the proper cure is to change the slide with the correct leaner or richer cutaway.
 
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In the 1970s I had a tuned 750 with 32 mm Amals that stumbled off the pilot onto the silde cutaway. I tried a 3 and a 3.5 cuaway but couldnt cure the fault. Finally I decided that it needed a 3.25 cutaway slide which I got by filing the no 3 cutaway slide to halfway to a 3.5.slide. result? The engine then pulled cleanly, much better than before . P.S. I had no Colourtune then.
Maybe that is the fault the 0P is having with his single carb.
 
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Fine tuning issues aside the first thing the op needs to do is see if the carb was fitted with 17 pilot jets and replace them with 19's. All the back and forth about transition tuning is a moot point if the pilot jet is wrong.
 
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I always set my idle circuit on the slightly rich side of the perfect bunsen burner blue using the Colortune.
That's exactly what I do, the quickest way to get the carbs right for the best acceleration from a standstill by far. But once again everything else has to be right, from ignition timing to the correct jets/slides in carb(s) - and I only use it on a dark moonless night.
(But if you alter one thing, you may have to go back over your setting that you have just done, again. You have to carefully think of what you do, and try and be one step aheard of yourself)
 
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What idle jets did your carb come with? Many suppliers fit them with #17's. These are generally too lean and #19's need to be fitted especially on 850's. The idle jets are the cross head screw on the opposite side of the carb from the mixture screw. Remove one carb and unscrew them to see what you have. The sizes are identified by rings on the jet. Two rings are 17's, three rings are 19's.
I wish I'd seen this before now... I had the carbs off this weekend for inspection and cleaning (even though they are brand new as of 5 weeks ago) - I checked the needle size and clip placement, cleaned both thoroughly, replaced gaskets, then reinstalled.

I am struggling horribly with this. I would welcome a phone conversation if you'd allow it. If so, you can text me at 6192047505 (San Diego, CA) and I will call back...
 
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Chris, I don't have new amal premier carbs. I have old amal carbs. The designs are similar, BUT,... as Htown said, the premiers were being sent out with #17 idle jets in them, and it seems like everyone who bought them has to change the idle jets out to #19 size.

On my original amal carbs, the idle jets are pressed into the recess opposite the idle air screw, so they are fixed in place and there's no access to them. If you have premiers you can access the idle jets and change them. You certainly need to check your carbs to see what size idle jets your carbs have. You should hope they are currently the wrong size, because then you've probably found your problem, and the correct idle jets will solve your problem...
 
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I wish I'd seen this before now... I had the carbs off this weekend for inspection and cleaning (even though they are brand new as of 5 weeks ago) - I checked the needle size and clip placement, cleaned both thoroughly, replaced gaskets, then reinstalled.

I am struggling horribly with this. I would welcome a phone conversation if you'd allow it. If so, you can text me at 6192047505 (San Diego, CA) and I will call back...
I just order a new set of 932 premiers and installed them over the weekend. 1973 850 - after looking around on here I asked for the following:

- #19 idle jet
- 106 Needle (it arrived in position three (bottom clip position (richest)) which is where I kept it and it runs well)
- 206 Main
- 3 1/2 slide

Finished tuning it up and it goes places quickly, just fine tuning. Right side air screw turned about one full turn out, left side almost 2 full turns). No stumbling off idle without dragging the clutch and not giving too much gas.
 
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I just order a new set of 932 premiers and installed them over the weekend. 1973 850 - after looking around on here I asked for the following:

- #19 idle jet
- 106 Needle (it arrived in position three (bottom clip position (richest)) which is where I kept it and it runs well)
- 206 Main
- 3 1/2 slide

Finished tuning it up and it goes places quickly, just fine tuning. Right side air screw turned about one full turn out, left side almost 2 full turns). No stumbling off idle without dragging the clutch and not giving too much gas.
Hello Eric,

I also have a 73' 850 - my new Amal 932 carbs list out as:

RJ 17
106 needle (I set the clips on the middle notch - (I live at sea level in a temperate climate)
260 main
3.5 sleeve

Prior to installing, I set the slides at 1/16 inch height on the fuel side (by eyeball) - but have jimmied with it so much I now reset the slide height by using a 7/32 drill bit (smooth end) on the cutaway side (raise the slide till the drill bit dips slightly). I can start it, get the idle strong at about 1300 - but when I lower the slides and it dips below 1000 rpm it will stumble and die. Most often when I twist the throttle to get revs, it seems to drown in air. I start with the pilot screw at 1 & 1/4 turns on both sides - and they typically stay within a quarter turn from there - most often clockwise (in) to richen)

Two full weekends of trying to dial it in and I'm at my wits end. I'm ready to hire a pro, or toss it off a bluff.
 
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Hello Eric,

I also have a 73' 850 - my new Amal 932 carbs list out as:

RJ 17
106 needle (I set the clips on the middle notch - (I live at sea level in a temperate climate)
260 main
3.5 sleeve

Prior to installing, I set the slides at 1/16 inch height on the fuel side (by eyeball) - but have jimmied with it so much I now reset the slide height by using a 7/32 drill bit (smooth end) on the cutaway side (raise the slide till the drill bit dips slightly). I can start it, get the idle strong at about 1300 - but when I lower the slides and it dips below 1000 rpm it will stumble and die. Most often when I twist the throttle to get revs, it seems to drown in air. I start with the pilot screw at 1 & 1/4 turns on both sides - and they typically stay within a quarter turn from there - most often clockwise (in) to richen)

Two full weekends of trying to dial it in and I'm at my wits end. I'm ready to hire a pro, or toss it off a bluff.
Hi Chris - Not sure how new you are with these things so my apologies if my response sounds silly but if things are a little bit off - the bike will do awful things. I've been shocked by what being off on carbs (what you would think is not much) just will make the bike feel like its about to explode. If i were you I might try the Number 19 pilot jet and see if that helps. That seems to cause a lot of 850 bikes to run lean. The pilot jet and the slide height are the only things that will effect at ilde so the rest is basically irrelevant. I doubt a brand new carb is dirty. I used a 3/16" drill bit to set my slides and they are running about at that height now ( i marked it on the carb body). How quickly are you taking down the idle? If it's at 1300 and running fine after you start it - I might take it out for 5 miles like that then come back and bring it down slowly in exactly the same increments on each side. Have you already done an exercise like that? Also what do you mean by drowning in air when you rev it? If you rev it and it goes up in rpm and sticks there and takes a long time to come down it’s too much air. If you rev it and it drops back down below where you started and either slowly comes back up or dies it’s rich.
 
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