Amal Throttle Stop Screw Question

Hi Everybody,
I have an Amal question : It is stated as boiler plate to always set the throttle stop screws mechanically equal. I use a .201 drill bit and engage the screws until it is a slip fit in the carburetor bore--I mark the screw position and mover equally up or down from there. My question is : in real world carburetors and cylinder head ports, does this always work out to be the optimal setting strategy?? Might not actual carb/head systems end up with some amount of offset between carbs for the most equal pulses at the tailpipe?
Very Sincerely,
Kara

Good for initial setup only. Nothing wrong in your procedure. Ignition timing variation, F/A ratio mixture variation, valve adjustment variation, actual carburetor manufacture mechanical differences, etc, are all part of the tuning game.
Choice of actual ignition system can make a pretty big difference on idle speed based on idle speed timing advance. You do seem to be choosing a good starting position...then up or down from there. Now you will need to train your ear
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As Dave said. A starting point only. The objective at the carb end is to balance for optimal mixture and vacuum. The latter doesn't assume the slides will be at the same position at any point in the throttle range, you need gauges to dial them in for optimal running. But if you don't have them you can, as Dave said, learn listen for bias between the two (one cylinder picking up late, uneven pulses from exhaust etc.)

acadian said:

you need gauges to dial them in for optimal running

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Sorry to disagree with the gauges thing.
I've had several sets. I was not all that impressed with their lack of accuracy.
I ended up using (if really necessary ) mercury carb stix to validate the tune by ear thing.
The most impressive thing about the gauges was how they flew across the garage to end up in the trash can. 2 sets...
This idle tuning procedure is nice but the important syncronization for under load/ cruising is the IMPORTANT part and is much more elusive as has been proved on the brake dyno time and time again...

They are problematic to an extent, I agree, I've found the carbtune gauges will give me different readings based on the time of day, so I use them to get me in the ballpark and fine tune by ear/feel from there

dynodave said:

Sorry to disagree with the gauges thing.
I've had several sets. I was not all that impressed with their lack of accuracy.
I ended up using (if really necessary ) mercury carb stix to validate the tune by ear thing.
The most impressive thing about the gauges was how they flew across the garage to end up in the trash can. 2 sets...
This idle tuning procedure is nice but the important syncronization for under load/ cruising is the IMPORTANT part and is much more elusive as has been proved on the brake dyno time and time again...

Click to expand...

+ 1 on mercury manometer....don't think they use mercury any more and its coloured water....H&S brigade probably
I have used gauges but I have never felt I get the same level of accuracy

I use a Harmonizer. Its great because I can view it while I ride to check all the throttle positions. I bought it through Far Horizon off of the Adventure Rider forum. Unfortunately the designer of the product passed away. Not sure if anyone else took it over. I use a colour tune to set my initial idle.

I generally use the drill bit method for initial syncing, this has served me well.

I also have a TwinMax that I use to double check if I have any doubt:


On a Norton it installs in place of the balance tube between carbs. IMO it takes, virtually, all the judgement out of carb syncing.

Two inputs, one transducer between the two vacuum sources, no mercury, no fluids of any kind, can be easily mounted on a tank bag or rubber pad and used for sync conditions under load. I purchased it to set the throttle bodies on an R1200 GS and it works quite well on the vacuum slide Keihans that do the mixing on my W650, what a sweetheart.

Best.

For setting the idle balance I put my hand close to the exhaust exit and you can feel if the cylinders are firing evenly. Especially easy with pea shooters.

If you are going to use any vacuum gauges, you need a damper knob, but this is still almost useless, you really have to set the tickover high enough by screwing in the slide stop screws untill the needle has settled down, then when you have got both carbs reading the same, equally lower the slides until you have a 1000 rpm tick over , - or whatever you set it at.