1975 RD125 Resto-rebuild

with 6 Comments
Yamaha RD125
Yamaha RD125

I bought this RD125 for my wife as an engagement present in the spring of 2016. I snuck around, borrowed a truck from a friend, took a day off work, ran halfway across the state, bought the bike, drove back home, snuck the bike into our garage, returned the pickup truck, then made it home at the same time I always got home. My wife never suspected a thing. When I proposed I surprised her with it and she was blown away! That’s the upside. The downside is that life has seriously gotten in the way of getting this little twin 125 on the road. The time for that rebuild and restoration is now.

I don’t plan on doing a full restoration. Parts for the RD125 are just too hard to come by these days to get this bike back to a perfect OEM state, and the bike isn’t particularly valuable or sought after anyways. This in mind, the plan is to keep it mostly stock, and most importantly get it running nicely. In the process of getting there, I will clean up the rust, replace anything that needs replacing, and generally make sure it’s safe to ride.

I have a good start on it. Over the last four years I have managed to replace the tires, work over the charging system, fix the turn signals, and replace the carburetors. The bike ran, but ran inconsistently as of last fall. The lead me to me to believe crank seals were due for replacing, of course, them being 45 years old should have been enough convincing.

The bike is mostly disassembled now. I have cleaned up a large number of the parts in the blast cabinet and am getting close to applying some powder coat. I also picked up a new toaster oven for curing the powder coat as my old oven was damaged in a flood. The motor is partly disassembled and once I have that finished, I will be ordering parts for it. A new chain and sprockets are on the way, new seat cover has been ordered, stainless engine bolts are coming, new keys (to replace the lost originals) are here already, and I’ll of course be building shocks for it too! Here are a few photos of the process, I will make new posts as updates continue.

6 Responses

  1. Ross
    | Reply

    Any update on the rebuild. I’m in the process of rebuilding one myself

    • Chris
      | Reply

      Ross,

      I haven’t done a lot to it recently but I plan to get back to it next week. The motor is ready to go back together. Cylinders are done, crank is rebuilt, the bike is on its wheels and looks okay. The tank and plastics need work, but I’ll worry about that in the fall.

      The plan is to get it running and then chip away at the remaining parts.

      Thanks,
      Chris

  2. Rob
    | Reply

    If you took pictures or videos disassembling your motor id really appreciate seeing them…a mechanic took mine apart honed the engine and rebuilt the crank and he didnt finish it so im having to do it myself… given quotes of $900 and $1500 i just cant pay that?
    Thanks

    • Chris
      | Reply

      Hi Rob,

      Sorry for not getting back to you sooner. I don’t have any videos, they would be terribly boring anyways.

      I use manuals from this site: http://www.yamaparts.com/manuals/

      – CL

  3. Rob
    | Reply

    Is there a shop manual you can recommend? I have one ready to reassemble as well(crank and barrels are done)
    Ive never rebuilt anything in my life…lol

  4. gary
    | Reply

    A RD 200 engine drops right it. Did it on girlfriend’s bike back in the late ’70’s. Can’t remember if I got the electric start to work.

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