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Wiring Diagrams / Schematics

Honda 250R with electrical problemsThe Honda ATC250R was in production from 1981 to 1986. Most enthusiasts would agree that the 1985 and 1986 models were the most popular, but there are those out there who stand by the earlier model years.

I posted these old wiring diagrams, or schematics, to help with troubleshooting in the event you are having an electrical problem.

They are easy to read and the wire colors are clear. If you know and understand these engine circuits, you will see that the electrical design of these Honda engines are remarkably similar to most other two stroke engines.

The biggest benefit of the engine schematic is, of course, the wire colors; the colors are essential for solving stubborn electrical problems...

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The CDI Box

In my experience with electrical problems on Honda ATC's, I know that it's very easy to blame the CDI. Engine electrical problems always seemed to point toward the big ticket item, the CDI unit. The CDI unit is a mystery box to most ATC mechanics. Those who are unsure of the source of their electrical problems always point toward the CDI unit because it's the easy scapegoat.

They are actually very reliable and durable electrical components. For those who would like some education on the matter, the CDI unit stands for "capacitive discharge ignition". Its sole purpose is to replace the old mechanical distributor style ignition of mechanical points. The CDI unit electronically raises the frequency and voltage created in your stator (or alternator) to thousands of volts, then it strategically energizes your spark plug with pinpoint accuracy.

It is far more efficient than those sloppy old points and distributor cap. In far too many cases, electrical do-it-yourselfers quickly assume they've got a bad CDI on board their Honda ATC whenever the engine won't start. Since CDI units usually don't have a black and white, bulletproof method of troubleshooting, they are often replaced unnecessarily. CDI replacement should be a last-ditch attempt to resolve your engine strating problems when all else has definitely been ruled out.

The problem of no spark can be many things. Always start with the simplest items because they are actually the most common sources of the "no spark" situation. Is the engine kill switch closed? Is the spark plug fouled? Are you electrical connectors corroded? Is a wiring harness unplugged? Do you have a broken wire?

Believe it or not, these are the most common reasons for a non-starting engine. It is not unusual for an ATC owner to assume the worst when the ATC won't fire up. Before throwing any parts at your ATC, be sure you have ruled out these common, and often easy to see, problems. Use the following wiring diagrams (wiring schematics) to assist with your ATC250R troubleshooting.


Wiring Diagrams

1981, 1982, 1983, 1984 250R wiring

Click or tap for full size view: 1981, 1982, 1983, 1984

1985, 1986 250R wiring

Click or tap for full size view: 1985, 1986


As a footnote, the ATC250R has ridden into the sunset from a manufacturers point of view, however, these off-road vehicles still have a quite a cult following. Whether you are planning to ride this weekend, or get started on a frame-up restoration, the electrical system is a critical component to the 250R.

I have also listed some ATC parts here. These are some of the more popular suppliers and may be worth a look.

And use the buttons below to share the glory of the legendary 250R... Keep on Ridin'...