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Harley-Davidson 45 WLDR & WR Front Drive Magneto
Beginning in 1939 the 45” WLDR & WR factory racing motor was equipped with a magneto driven horizontally from the generator position (although a vertically mounted Wico was also used 1948-49).
The magneto and driven gear used for the 1939 WLDR are not listed in the factory racing data; I have interpolated the appropriate numbers for the magneto and its drive gear; these are only a guess.
The drive was composed of eight separate and interconnected elements, two of them unique to this application, as shown below. The change of speed and transfer of motion takes place as follows: |
1. The 18 tooth pinion gear drives the #2 rear intake cam’s 36 tooth outer row at ½ engine speed.
2. The #2 cam’s 28 tooth inner row drives the 28 tooth #3 front intake cam at the same speed.
3. The 28 tooth #3 cam drives the #4 front exhaust cam’s 28 tooth inner row at the same speed.
4. The #4 cam’s 36 tooth outer row drives the 36 tooth idler at the same speed.
5. The 36 tooth idler rotates the 36 tooth magneto driven gear counter-clockwise at the correct ½-speed. |
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WR magneto front
drive components |
Component | Tooth Count |
Pinion gear | 18; std. |
#2 rear intake cam | 36; std.; outer row |
28; std.; inner row |
#3 front intake cam | 28 |
#4 front exhaust cam | 28; std.; inner row |
36; std.; outer row |
Idler gear | 36; unique to magneto |
Magneto driven gear | 36; unique to magneto | |
Please note that there is only one ratio/speed change (pinion gear to #2 cam outer row: 18/36); all other mated gear pairs have the same tooth count, so the correct ½ engine speed is preserved through to the magneto.
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Tracking the various components used over the years is somewhat confused by the H-D factory method of assigning part numbers, which changed twice during the critical period 1939-52. |
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Magneto Front Drive Part Nos |
Year | Component | Magneto | Idler | Driver |
1939 | Edison-Splitdorf | 1802-30 | 80619-39 | 0626-30 |
1940 WLDR | 81802-40 | 80626-40 |
1941-47 WR |
80619-41 |
1950-2 | Wico | 29504-50R | 29675-50R |
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Racing parts in the 1930’s used a 5-digit number, with “8” as the 1st digit, then the identifying characteristic, then the hyphen, and ending with the year. For example: a WR intake manifold for this period is 81107-40.
The next type began in the late 1940’s, with a 5-character number beginning with “R“ in place of the “8”, otherwise identical: R1107-40.
The last type is modern and current (195?-*), in which a 5-digit number with a different characteristic reference is used, then the hyphen & year, with the letter “R” as a suffix, as: 27020-40R. |
A std. WL, G etc. right crankcase will require complex modification to use the front drive magneto. As shown in the picture (courtesy of Beauty of Speed), various machining (and possibly welding) operations are needed to the interior of the right crankcase half to either move or add to the existing generator idler post and boss, since the magneto idler gear is smaller than the generator idler. The support boss inside the cam chest cover must also be re-located; here is a 1941 WLDR cover (again, courtesy of Beauty of Speed) with both idler post positions (the hole to the left is magneto).
As in all magnetos of this type, ignition timing is fixed. There is no automatic (centrifugal) advance mechanism or retard feature for starting. There is no method of timing the ignition advance without removing the cam chest cover, magneto, etc. This is unlike the subsequent 1950-* WR front drive system, in which two vernier plates permit very small adjustments to be made through an access cover. I have no pictures or other details. |
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Click the picture, right, for a much larger view of the H-D factory 1950-* vernier-style adjustments on a separate screen.
Please note that these parts will not fit the 1937-48 U-Series or 1936-69 OHV motors, as the pinion gear tooth count is different (18 vs. 20 or 21), along with many other dimensional differences. I have some comments on these installations, click to see 1936-69 OHV:  .
Contributions and corrections welcome as always, e-mail text and jpgs (or URL) to: jdiamond@optonline.net. |
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