Vintage Dirt Bike Q & A

Hello,

I am glad to have found this website today and wanted to introduce myself and ask for help. I have already learned some things from reading your posts, thank you for that.

I am a not so mechanical person who has very little experience with engines. I know to check the oil and how to mix gas. Although I am not sure what ratio to use yet. My Father-in-law, a super guy, gave me a mr250 which I read moments ago is a 1976 year only bike. Anyways, it is running very well at the moment but the brake light and headlight do not work. I know this is not a big deal to some but I wanted to try to fix them to show that I appreciate the bike and that I am willing to learn about them.

I found the manual and am trying to understand the wiring diagram. I took a few pictures to show you what I am looking at as well. I have a tester (ohms meter) The bike has a new stator and rectifier and the kill switch works.

I thought about taking the tail light off and hooking it to a car battery to see if the bulb was good but this system is 6v and I wasn't sure if that would damage the bulb.

Do these pictures look pretty standard? On the headlight, I believe the blue wire coming in is the high beam, the white is the low beam and the green is ground so the ground could just plug into the green harness. Does that sound about right?

any ideas on the break lights

Hi,

Congratulations on your new acquisition!

With your meter set to the lowest ohms setting (short the leads together to make sure you get a reading and the meter's battery is OK), clip one lead to the green wire (or chassis ground) and then touch the other lead to the various black, white, and brown wires associated with the hi/lo headlight and taillight bulbs (unplug them from the wiring harness first, of course). You should get a low ohms reading on each of them; no reading at all means that bulb is toasted or there's a socket/connector/wiring fault.

It looks like your headlight wiring may have been modified to accept a single-filament (lo-beam-only) bulb. It appears the correct 34901-030-003 or 34901-087-640 headlight bulbs and 34902-202-000 taillight bulbs are still available from Honda.

Here's a link to a wiring diagram:

http://alp-sys.com/vintagedbforums/down ... &mode=view

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Ray: if I EVER get a bike with an electrical system or lights, I'm gonna have to get your cell phone number !! I referred a guy from another site to you and you helped him a great deal, I believe. Thanks in advance for the day I'll need your electrical troubleshooting help !

mitchie,

No problem at all ! ... except I'm probably the only guy on the East Coast without a cell phone . If you ever need help, just shoot me a PM and we'll take it from there.

I was an electronics tech for nearly 28 years, so hopefully I picked up at least a little stuff that's applicable to bikes along the way. Even though vintage MC electrical systems are pretty basic, they can still put up a good fight sometimes. One thing I've found is that a good meter can be essential to determine if an ignition is operating correctly, as opposed to simply putting out a spark.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric