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American Bosch Magneto Parts

American Bosch (originally Robert Bosch) built mags in Germany for the newly emerging gas engine industry starting around 1905 or so. Robert Bosch was probably one of the most prolific of the early magneto builders making many design innovations. His shuttle-wound armature design was copied by almost every other magneto builder of the time, but Bosch was always the best. A properly tuned DU4 with all new parts could jump a 7mm gap (almost 3/8") with very little effort. Bosch mags were used heavily in cars, trucks, tractors, motorcycles, stationary engines and airplanes. Their aviation mags were so popular, that they adopted "Fritz The Flyer" as their company as their company mascot, and that appeared on many of their mags. Their official company logo, the armature, was used on many of their early mags and is still used today by their power tool division.

During and after WW I, German assets were seized by the US government and sold to the highest bidder under the Trading With The Enemy act. The Robert was dropped from the name and they became simply known as "Bosch". This did not sit well with many American consumers who recognized the German "Bosch" name. The name was quick changed to American Bosch and production continued in the US under that name for quite some time. One of their largest contracts was for an ultra-compact and low-cost mag to be used by Fairbanks-Morse, the AB33. After many years and many engines, Fairbanks-Morse asked American Bosch to try and reduce the cost of the mag. The reduced cost version became known as the AB34. This proved to have some manufacturing problems and Fairbanks asked Bosch to switch back after only 1 year. Today it is somewhat rare to find an AB34 on an engine.

Over the years, the name changed back and forth, all variants seemed to be used interchangeably. Today, Bosch no longer makes magnetos or their parts. Their rights have been sold off to aftermarket vendors. Some parts are available for their modern mags. The more common ones are listed below. I can get many other parts, but I generally do not stock them. There are over 600 parts available for these modern mags. I have also put together a susbsitutions table for some of the discontinued parts. It is not all good news, many of the substitute parts have been discontinued, but what can you do.... It is better than nothing.

Check out this company history from the Bosch web site <click here for Bosch history>

As for the old mags, there are very few parts to fail on them. I can rebuild condensers (these are located in the end of the armature) and have coils rewound. This is all done on an exchange basis. I can also make some of the leadout towers. Please ask with your needs. Points can generally be saved with a good honing with a diamond file. If they are beyond salvage, I can put on new tungsten. Oscillating versions of these mags are essentially the same as the rotary ones. I can usually find some springs to replace bad or missing ones. I make rollers and can also make the posts if I have one to go by.

Parts for the AB33 and AB34 are listed under Fairbanks-Morse magneto parts (since they were used exclusively on Fairbanks Morse engines.)

Just received!!! Lead out towers for Bosch ZEV magnetos. These were commonly used on Indian and early Harley Davidson motorcycles. Each comes with a brush, spring, and wire piercing screw.

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AB33/34 Magneto Parts

DU, U, AT, ZR, ZE, ZEV, & Many Other Older Mag Parts

Modern Mag Parts

 

Order number

Description

Picture

Price each

 DU6, DU4, DU2, DU1, U4, AT4, & many other older mags

CND20

Condenser rebuild, you send me your condenser, I install a new modern-style condenser

 

25.00

CLR20

Coil rewind, DU1,2,4,6 & many other single spark coils

 

130.00

CLR21

Coil rewind, U4 & many other single spark coils

 

130.00

 

I can have almost every Bosch, Robert Bosch, & American Bosch coil rewound. Please call, e-mail, or write with requests

 

 

FM030

Roller, spring, (hardened)

 

4.00

FM034

Spring, oscillator, most

 

5.00

BRG02

Bearing, type E15, three piece take apart, inner race, outer race, bearing cage

 

25.00

AB100

ZEV spark plug wire lead out tower, left hand, with brush

 

35.00

AB101

ZEV spark plug wire lead out tower, right hand, with brush

 

35.00

Modern Rotary Mags

MJA, MJB Variable & Fixed Timing Rotary Mags

 

 

 

 

AB11

Condenser, CW5210, MJA ed A,B,C, MJB, MRA & MRF variable

 

24.00

AB12

Condenser, CW5291, MJA ed D, MJB ed B, MRA &MRF fixed

24.00

AB13

Condenser, CW5279, MJH, MRD, MSA, MSB

 

24.00

AB20

Points, CS521, MJA, MJB, MRA, MRF, MRB

 

18.00

AB30

Coil, a generic replacement, CL521043

 

75.00

AB60

Gasket, control arm cover, MJA, MJB, GA521

 

2.00

AB67

Gasket, cap, MJA, GA522

 

6.00

AB61

Gasket, cap, MJB, GA523

 

3.00

AB46

Distributor rotor, MJA 4 cylinder, RT52418AS, *** special order

 

115.00

AB47

Distributor rotor, MJA 6 cylinder, RT52422AS, *** special order

 

100.00

AB48

Distributor rotor, MJB 4 cylinder, RT52425AS, *** special order

 

85.00

AB49

Distributor rotor, MJB 6 cylinder, RT52426AS, *** special order

 

90.00

MJC Rotary Mags

AB14

Condenser, CW5232

 

28.00

 

 

 

 

AB23

Points, late (most) CS522

 

 

AB30

Coil, a generic replacement, CL521043

 

75.00

MJH Rotary Mags

AB13

Condenser, CW5279, MJH, MRD, MSA, MSB

 

24.00

AB21

Points, BK52203, MJH, MRD, MSA, MSB, TDG

 

18.00

AB30

Coil, a generic replacement, CL521043

 

75.00

AB80

Rotor, RT52288, MJH edition C only, 2 & 4 cyl

 

40.00

AB81

Rotor, RT52304, MJH edition C only, 6 cyl

 

40.00

AB62

Gasket, cap, MJH, GA5261

 

1.50

MJK Rotary Mags

AB10

Condenser, flange mount, CW52110, MJK, commonly used on Cat starting engines

 

38.00

AB22

Points, BK52234, MJK, commonly used on Cat starting engines

 

35.00

AB45

Rotor, MJK, RT52154PAS, commonly used on Cat starting engines

 

80.00

 

 

 

 

AB31

Coil, CL5298

 

75.00

AB51

Cap, DP52442, lead-outs diagonally across from each other, ** special order **

 

120.00

AB65

Cap gasket, GA52148

 

6.00

AB66

Rear gasket, GA52157

 

7.00

AB55

Gear, distributor, MJK 4/2 360o, GE52280, ** special order **

 

65.00

AB56

Gear, distributor, MJK 4/2 180o, GE52278, ** special order **

 

65.00

AB70 

Seal, MJK editions C & D, PK5237

 

5.00 

AB73

Bronze bearing, edition "D" mags only, BG52160

 

 

MRA, MRB Rotary Mags

AB11

Condenser, CW5210, MRA & MRF variable timing

 

24.00

AB12

Condenser, CW5291, MRA & MRF fixed timing

24.00

AB20

Points, CS521, MRA, MRF, MRB

 

18.00

AB52

Coil, CL52164, MRA, ** special order **

 

180.00

MRD Rotary Mags

AB13

Condenser, CW5279, MJH, MRD, MSA, MSB

 

10.00

AB21

Points, BK52203, MJH, MRD, MSA, MSB, TDG

 

18.00

AB64

Cam Felt, MRD

 

2.50

AB30

Coil, CL521043

 

75.00

AB40

Brush & spring, BR173

 

8.00

AB50

Cap, 1 cylinder, MRD, DP521005

 

30.00

AB82

Cap, 4 cylinder, MRD, DP52607, ** special order **

 

160.00

AB83 

Cap, 6 cylinder, MRD, DP52610, ** special order ** 

 

170.00 

AB80

Rotor, RT52288, MRD, 2 & 4 cyl

 

40.00

AB81 

Rotor, RT52304, MRD, 6 cyl

 

40.00 

AB84

Gear, distributor, 4 cyl, GE52238, ** special order **

 

55.00

AB85

Gear, distributor, 6 cyl, GE52243, ** special order **

 

50.00

AB63

Gasket, flange, SAE

 

1.50

AB70

Seal, PK5237

 

5.00

AB71

Seal, SE3004

 

6.00

Impulse Parts

AB72

Impulse coupling disk, 2 " OD, 1" ID, DC739-1

 

25.00

AB75

Impulse spring, compression type, spring with 2 ball bearings

 

30.00