For the base-mount WICO magneto described by Ron Van Zee, set the adjustable inner index trip ring according to the magneto’s lug: 4½ marks left of 12 o’clock for a 35° lug, or 1½ marks left for a 25° lug. Identify the lug before applying either setting; these are configuration-specific instructions, not universal magneto specifications.
Identify the WICO magneto and lug first
The procedure below concerns a base-mount WICO magneto. The lug type matters because the two settings differ. Van Zee’s 2015 Successful Farming article describes an example with a 35° lug and notes that some magnetos use a 25° lug. Confirm the magneto and lug against the correct tractor and magneto service information before adjusting it.
Look past the impulse coupling for the V-shaped trip attached to the adjustable inner index trip ring. With the appropriate lug identified, set the ring as follows, then tighten its retaining screws:
| Lug configuration | Index-ring position |
|---|---|
| 35° lug | 4½ marks left of 12 o’clock |
| 25° lug | 1½ marks left of 12 o’clock |
These positions are the settings reported in Ron Van Zee’s November 3, 2015 article, “Rustoration 101: Timing a Magneto”. They should not be treated as a full engine timing specification.
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#1 Best Overall
- Fits: John Deere- X, XH, XB4001L WICO series magnetos-
- All JJAgParts items have been hand selected by our team and are continuously monitored for Quality. Should a craftsmanship or fitment concern be identified, JJAgParts will work with you to stand behind our products. JJAgParts is an American owned and operated family business!
- Here at JJAgParts, we strive for customer satisfaction. If you are not satisfied with your order, please contact us so we can make it right. Note: OEM Part Numbers are for reference only and should be verified before purchase.
Prepare the ignition system
Van Zee reports magneto expert Cork Groth’s recommendation to replace the ignition switch and all electrical wiring before timing and installing a tractor magneto. For spark-plug leads, the article specifies non-resistor copper wire with new brass tips soldered to the wire.
Install the magneto and check the impulse
- Engage the coupling: Fit the magneto’s two fingers into the appropriate slots in the governor or camshaft coupling.
- Turn the engine slowly: Check that the magneto impulse clicks when the piston is at top dead center (TDC), as described in the article.
- Make a fine adjustment only if applicable: Some magnetos have slotted mounting-plate holes for adjustment. Use the correct model-specific service information for the required timing and any allowable tolerance.
The reported TDC click is an installation check; it does not supply the tractor’s complete firing-angle specification or full instructions for positioning the engine.
Rank #2
- Compatible with John Deere Tractor(s) A, AO, AR, B, D, G, GH, L, LA, LI, R
- Replaces John Deere OEM Number(s) AR12006
- Replaces Wico Mfg Number(s) X5700C
What the spark check does—and does not—tell you
Van Zee reports Groth’s test-stand observation that a magneto in good condition produces a hot blue-white spark extending about ¼ inch when the impulse is tripped and the magneto turns at engine operating speed. Treat this as the article’s reported criterion, not as an independently established universal standard or a substitute for model-specific testing.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Use tractor-specific safety and timing information
A magneto can generate ignition independently of the battery or ignition switch, so switch position or battery state alone should not be assumed to make magneto work safe. The available safety discussion is about aircraft magnetos, not tractor isolation procedures; consult the correct tractor and WICO service information for safe handling and work practices.
Rank #3
- Fits: International (Wico mags only, will NOT fit IH mags) I4 AV Super A B BN C Super C H HV Super H I9 M Super M MTA MV O4 O6 OS6 T6 W4 W6 W6TA; John Deere A B AO AR BO BR D G H LA R(pony mag); Allis Chalmers (w Wico replacement mag) B C RC WC WD WF; Case (w Wico mag only, will NOT fit Case mags) S SC D DC DI DO SI SO
- Replaces PNs: International X5700; John Deere AR12006R, X5700, Wico X5700B
- All JJAgParts items have been hand selected by our team and are continuously monitored for Quality. Should a craftsmanship or fitment concern be identified, JJAgParts will work with you to stand behind our products. JJAgParts is an American owned and operated family business!
- Here at JJAgParts, we strive for customer satisfaction. If you are not satisfied with your order, please contact us so we can make it right. Note: OEM Part Numbers are for reference only and should be verified before purchase.
The Continental S-20/S-200 aircraft magneto manual lists an E-50 timing light or equivalent for checking magneto-to-engine timing and an 11-8150-1 timing kit for internal timing. Those references show that physical timing tools are used for magneto service, but they do not establish that those tools or aircraft procedures apply to a tractor WICO magneto. Verify any timing light’s compatibility with your engine and magneto before use.
Quick Recap
Best Value
- Compatible with John Deere Backhoe Loader(s) 50
- Compatible with John Deere Tractor(s) A, ANH, AO, AR, B, BN, BNH, BO, BR, D, G, GH, GM, GN, GW, H, HNH, HWH, 50, 60
- Replaces John Deere OEM Number(s) X2938
- For Wico Magneto Number(s) C
- Top cap where the plug wires connect
Rank #4
- Magneto tune up kit for the Wico X. Points, condenser and rotor in one box, which is the whole ignition service on these tractors short of the cap, the coil and the impulse coupling
- Wico X only. A tractor that left the factory with a Wico C or an XH takes a different kit, so lift the cap and read the tag on the magneto body before ordering rather than going by the tractor model
- Fits John Deere A, AO, AR, B, BO, BR, D, G, H and R tractors built with the Wico X magneto. Hard starting, a thin blue spark or no spark after a winter in the shed is usually points and condenser
- Replaces R6847. Set the point gap to specification with the magneto at full separation, because a set gapped by eye will fire on the bench and still not make the spark it should at cranking speed
- Aftermarket replacement, not an OEM part. Points, condenser and rotor only. The cap, the coil and the impulse coupling are separate parts, so check those as well if new points do not bring spark back
Sources
- Ron Van Zee, “Rustoration 101: Timing a Magneto,” Agriculture.com / Successful Farming, November 3, 2015. Read the article.
- Continental Motors, S-20/S-200 Series High Tension Magneto Service Support Manual, August 31, 2011. The manual concerns aircraft magnetos and is not a tractor WICO service guide.
- Bill Ross, “Magneto Maintenance 101,” Cessna Flyer Association. The article discusses aircraft magnetos; its publication date is not established.
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