Throttle disc 27714-66

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panhead_kicker
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Throttle disc 27714-66

#1

Post by panhead_kicker »

I made the mistake of removing the throttle disc 27714-66 from my Tillotson HD2D before realizing its not the same from both sides. One side has a dash imprinted, and the circumference looks to have a slight bevel towards the opposite side.
Does anyone have documents that describe the correct orientation? 69 service manual doesn’t seem to address this.
*edit* closer inspection shows the bevel changes sides , from top to bottom. So it would make sense the bevel would follow the angle of the disc seated in the bore.
This lets you see the imprinted dash , looking into the bore from choke side.
Mongrel505558
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Re: Throttle disc 27714-66

#2

Post by Mongrel505558 »

If it's like any other butterfly carburetor, the bevel, or angled edge of the throttle plate, will be parallel with the bore when in the closed position. I can't imagine any reason for doing the opposite.
kitabel
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Re: Throttle disc 27714-66

#3

Post by kitabel »

The disc never completely closes. The bevel determines when the edge of the disc passes through the idle and transition holes, and largely controls off-idle response.
Smaller angles (the MR-4 1-1/2" Model M bevel is 8 degree) have richer tip-in than larger angles (all 1-1/4" Model M are 13 degrees).
In addition, a small amount of material may be removed to alter this characteristic: the 1-1/2" M-74B uses a 9X, the bevel mod is at 6:00 o'clock.

[image]https://www.picclickimg.com/d/l400/pict ... te-9-X.jpg[/image]
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Re: Throttle disc 27714-66

#4

Post by panheadrider1961 »

can you post picture of both sides?
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Re: Throttle disc 27714-66

#5

Post by kitabel »

Other side is blank, only the beveled area has any effect on mixture.
With the correct carburetor and disc etc. the idle speed will place the disc edge between the small idle and transition holes. If your idle speed is too low with the disc in proper alignment (not likely to happen), air can be admitted to the manifold through a small hole on the disc.
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Re: Throttle disc 27714-66

#6

Post by panhead_kicker »

panheadrider1961 wrote: Sun Aug 28, 2022 9:45 pm can you post picture of both sides?
65382125-5BAB-4EC7-94E8-00CA1DE27EF0.jpeg
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panheadrider1961
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Re: Throttle disc 27714-66

#7

Post by panheadrider1961 »

First picture is screw side see outline of impression from screw heads and last picture see outline of shaft centerline put it back on shaft side and screw side then bevel should be back where it is needed at bleed port make sure you don’t turn it 180 out bevel and hole should be aligned hope this helps
panhead_kicker
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Re: Throttle disc 27714-66

#8

Post by panhead_kicker »

panheadrider1961 wrote: Tue Aug 30, 2022 3:09 pm First picture is screw side see outline of impression from screw heads and last picture see outline of shaft centerline put it back on shaft side and screw side then bevel should be back where it is needed at bleed port make sure you don’t turn it 180 out bevel and hole should be aligned hope this helps
Actually, the throttle lever is slotted so the screw heads never land on the disc, but good effort! I have found some original documents on this carb describing the proper orientation, which is as everyone has stated; bevels parallel to the bore.
panheadrider1961
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Re: Throttle disc 27714-66

#9

Post by panheadrider1961 »

Good deal
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