Monday, May 6, 2013

PROJECT SR250: Wiring, Assembly and Testfire

According to my calculations an update to the Yamaha SR250 is long over due. I've been working at full speed the past few weeks after a certain calendar event invite from Kara regarding completion of her sweet summer ride. 

The biggest hang up for me, mentally, was wiring up a new harness from scratch. Wiring diagrams weren't covered in my art school education. The best I could do is paint you a picture describing what they mean to me. Many parts on the bike were either relocated or replaced by parts with different electrical needs. I picked up as many wire color combinations I could find and some fresh connectors ( - highly recommended) then gave my auto tech / mech. engineering friend Joe a call. He's been kind enough to lend a hand whenever I find myself standing and starring at a project for 20-30 minutes visualizing how difficult it's going to be.

We started by mapping everything out that would be on the new harness and cross referencing the stock diagram for where lines would need to run. This took a while but helped tremendously down the line when we needed to diagnose some issues, like a flashing headlight.

After about 7 days worth of drawing up diagrams, running leads, cutting lengths and making new connectors, we hooked everything up and tested all elements to verify we did it correctly (we didn't). Our main problem resulted from us not having enough color combos and using the same color twice. My advice would be to match all color combinations with the stock colors - this would have saved many headaches and translation issues. After that was sorted I wrapped everything using abrasion resistant harness tape made by Tesa.

I added some final touches to the electronics box, put everything back on the bike, poured in some fresh oil and gave it a go. You can' task for a result much better then this from a bike that's been on a table for a year:
Last night was the first test ride. She made it around the block a few times but is having trouble idling. I'll be working on getting the carb dialed in this week and hopefully get to take her on a real test ride. For those of you interested in seeing the final product in person, I'm aiming at getting everything wrapped up for the Chicago Mods vs. Rockers show June 14-15. More updates will be on their way.


  1. Looks great. Thanks for the link to the re-wiring kit, I'm going to have to attempt the same on my 69 CL 175 in a the coming months. I've got to say I love the blog. Awesome features, and you've given me the guts to try and restore a bike of my own.

  2. ^ What Daniel said. Great blog, man. Love the details.

  3. Posh Switch: Any issues running a 3-amp headlight switch on the CX500 (~5amp i think) system?
    Thanks, Ben

  4. Amazing coverage, amazing photos, and sexy looking bike. Nice job with the diagrams too!

  5. electrics have to be the hairiest part of motorcycle rehab. can you recommend a book or website that explains it all for the electrically impaired?

    1. Most good repair manuals have a section that teaches you to read wiring diagrams. On too of that I would learn the basics of testing with a multimeter (YouTube). Once you fully understand both concepts you can fill in the gaps.