Amal slide cutaway differences

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Dec 19, 2004
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Greetings all,
I presently have #3 slides in my Amals, I would like to go to #3.5.
I know I could purchase the #3.5s, but, my carbs have previously been resleeved. I could be wrong, but, I doubt anyone is offering pre-sleeved slides for sale (well maybe used ones).
I have considered cutting them myself, but, without a #3.5 in my hand I have no idea what the dimensional change is. I was hoping someone could enlighten me. IE 0.5mm, 1mm, 2mm??? are we talking shallower angle, steeper angle, or same angle???

info appreciated,

I believe that the cutaway angle on a #3 and a #3.5 slide is the same; I;ll double check when I get home. The difference between the two is the amount of cutaway.

The company that sleeved your carb slides should be able to provide you with #3.5 slides. Alternatively, you can carefully sand your #3 slide to make a #3.5 slide with 320 grit sand paper. Use a panel of glass to ensure uniform removal of material from the slide.

What makes you think you need a #3.5 slide? What symptoms are you experiencing?


Ok, I just measured the cutaway height on my #3.5 slides and came up with .217". According to Dynodave a #3 slide is .188" (3/16") and each half step is .031" (1/32"). In theory then a #3.5 slide cutaway height should be: .188" + .031 = .219". As such my .217" measured height is pretty darn close to Dynodave's information.

And as Dynodave mentioned, the angle of cutaway does change. I confirmed this when I compared a #3 to a #3.5 cutaway when I got home from work today. However, I don't think it's too critical in the overall scheme of things.

So, get out your flat piece of glass or other flat surface and sand down your #3 slides unitl you have a #3.5 cutaway height of .219". And don't worry too much about the angle. Check your progress periodicly using a verneer caliper. First measure the overall height of the slide. Next measure from the cutaway to the top of the slide. Then subtract the two dimensions and you will have a pretty accurate dimension of the cutaway height.

I'm leaving town to visit my brother in Fort Worth, Texas tomorrow, which may put me out of touch for a couple of days. So, I'd like to take this opportunity to say: MERRY CHRISTMAS EVERYONE!


Thanks for info

Dave and Jason,
Thanks for providing those figueres. I am in the middle of a few winter upgrades as I'm sure most everyone is. Presently the bike is in my shop strapped to my lift:

1. Single Amal conversion
2. Primary belt drive (RGM unit via Clubmanracing)
3. Tie rod headsteady (copied with improvements from
an article posted on Captain Nortons Notes)
4. May just fab up some rearsets if time permits

Happy Holidays,
cutaway angles

Hi Guys:
The cutaway angle on a #3 is 20 Deg and a #31/2 is 23 Deg.
It makes about a 1/16 difference. Sometimes when I Bore and sleeve the carbs they run a little rich for awhile. If you swivel a sanding table to 20 deg. you can confirm it is 20 Deg. Then swivel it to 23 Deg. and lightly sand the difference off til it blends at the bottom area. If anyone needs angles for others let me know.
cutaway math

1. The cutaway starts at the outer edged of the idle stop slot.
Therefore the cutaway angle starts there.

2. A stock slide (pn928) yeilds .57 inches... that gives the base of the triangle for the angle.

3. Doing the rise for the angle using 2-1/2, 3, 3-1/2, and 4 also using 1/16 (.0625") for a full cutaway, yields these angles,

(opposite over adjacent is what I was trying for also, darn calculator buttons........Jasons numbers are better)


that's how I see it.
I hope everyone had a great Christmas! I got a chance to see some really intersting vintage European motorcyles in Fort Worth over Christmas; the most interesting was a Munch Mammoth!

I noticed we managed to get off track a bit on the carburetor slide angles. I maintain that the anlge is not super critical; it's the increase or decrease in the volume of the cutaway void that changes the air/fuel mixture. And as Dynodave suggested, you should start the angle at the throttle stop slot when modifying your slides. Good advice.

However, for sport I double checked the posted angles using Dynodave's dimensions and found some discrepancies. I used trigonometry to calculate the angles: Tangent of the angle = oppposite side (rise) divided by adjacent side (base) of the triangle. Following are the results of these basic trigonometry calculations:

But again, its the volume of the void in the slide that matters most. It's prudent to take off a little bit of material at a time and assemble the slides in the carburetors for a trial run. The end result of this trial and error method is that you may find that an in-between size works best.
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