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 armeture 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, motorcyles, 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 armeture, 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 chenged 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 manufactoring 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 interchangably. 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 armeture) 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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DU, U, AT, ZR, ZE, ZEV, & Many Other Older Mag Parts
| Order number | Description | Picture | Price each |
| 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 | |
|
MJA, MJB Variable & Fixed Timing Rotary Mags |
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| AB11 | Condenser, CW5210, MJA ed A,B,C, MJB, MRA & MRF variable |  |
12.00 |
| AB12 | Condenser, CW5291, MJA ed D, MJB ed B, MRA &MRF fixed | 10.00 | |
| AB13 | Condenser, CW5279, MJH, MRD, MSA, MSB | 10.00 | |
| AB20 | Points, CS521, MJA, MJB, MRA, MRF, MRB |  |
14.00 |
| 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 |
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| AB14 | Condenser, CW5232 | 28.00 | |
| AB30 | Coil, a generic replacement, CL521043 | 75.00 | |
|
MJH Rotary Mags |
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| AB13 | Condenser, CW5279, MJH, MRD, MSA, MSB | 10.00 | |
| 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 |
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| AB10 | Condenser, flange mount, CW52110, MJK, commonly used on Cat starting engines |  |
10.00 |
| AB22 | Points, BK52234, MJK, commonly used on Cat starting engines |  |
30.00 |
| AB45 | Rotor, MJK, RT52154PAS, ** special order **, commonly used on Cat starting engines |  |
80.00 |
| AB30 | Coil, a generic replacement, CL521043 | 75.00 | |
| AB31 | Coil, CL5298, ** special order ** | 170.00 | |
| AB51 | Cap, DP52442, lead-outs diagonally across from each other, ** special order ** | 120.00 | |
| AB65 | Cap gasket, GA52148 | 6.99 | |
| 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 |
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| AB11 | Condenser, CW5210, MRA & MRF variable timing | |
12.00 |
| AB12 | Condenser, CW5291, MRA & MRF fixed timing | 10.00 | |
| AB20 | Points, CS521, MRA, MRF, MRB | |
14.00 |
| AB52 | Coil, CL52164, MRA, ** special order ** | 180.00 | |
|
MRD Rotary Mags |
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| 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, BR521005 |  |
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 |
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| AB72 | Impulse coupling disk, 2 ½" OD, 1" ID, DC739-1 | 25.00 | |
| AB75 | Impulse spring, compression type, spring with 2 ball bearings | 30.00 | |