flywheel diameter?

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I've been messing with timing, and it started me wondering how many degrees you can see in the inspection window on the flywheel cover. I can measure the size of the window--can anyone with a spare flywheel tell me what the diameter is? From those two I figure I can calculate the circumference, and from that how much advance or retard is represented by the span of the window. I'll post back to the thread if someonce can shoot me the diameter.

Or better yet, does anyone know already? :idea:
 
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Since I have one sitting on the floor-
ring inner diameter is 12.60" (best I can measure)
OD is 12.85 (flywheel, not the ring gear)
and C= 40 5/8" measured with a cloth tape.

hth

t
 
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Since I have one sitting on the floor-
ring inner diameter is 12.60" (best I can measure)
OD is 12.85 (flywheel, not the ring gear)
and C= 40 5/8" measured with a cloth tape.

hth

t
Sweet. Thanks so much Toby!

So which line did you use to measure "ring inner diameter"?
See picture below

How about OD of the flywheel (not the ring gear)?

I'm assuming C is the circumference, which must include the height of the gear teeth too, right?

Thx.
 

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Joined
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I measured at B, the split between the flywheel and the ring gear. There's a shoulder that's turned down
a bit under the flywheel diameter.
The diameter is the outer diameter of the flywheel itself (the ring gear is bigger, but I didn't measure that...)
as is the circumference. pi d should equal the circumference... and it's close, but not exact.
I used a cloth tape for the circumference, and my digital calipers only go to 12", so neither
dimension is accurate to more than .1" !!


t
 

Mace

rock scientist..
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Line to the BB is 7 deg. Easier to measure.
 
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Line to the BB is 7 deg. Easier to measure.
Yeah, that's where I started. But I'm gonna try to mock up a timing tape on masking tape first. If that doesn't work, I make marks on the flywheel itself.

Have you done this? Measure ignition advance off the flywheel? You know a better way to do this?

There's gotta be a machine for it, but I'm just a lowly survival mechanic type...
 

Mace

rock scientist..
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Feb 17, 2002
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get a timing gun with an advance knob.. Set from there...

It really is that easy..

From fudge factor, it looks like 1" = 7* or so.. Tape won't last long on most cruiser flywheels. How much advance are you looking for? If you put the BB at the edge of the window, it's about 10*.
 
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I'm measuring advance at different rpms. At high rpms advance can go up above 35*?

I guess it might be possible to the use advance knob from a timing gun to take those measurements. Set rpm, then switch through the knob until the bb aligns with the pointer on the viewing window. Then add 7 to whatever setting is on the gun and that is total advance for that rpm.
But I don't have a gun with advancer knob on it...
 
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