1975 RD125 Build

[apgamer]

Hi all,

New to this board and this is a first for me as far as bike projects go. This will be my first cafe project and my first time working with a two stroke. I've got a built up DRZ440 motard but this will be my first major bike project as far as fabrication goes.

I picked it up without a title for $400. Yeah, I think I overpaid a little but I didn't really know what to look for. The lack of a title shouldn't be an issue since I'm from Maine and anything over 25 years or under 300cc doesn't need one.

It has 3000 original miles and hadn't been ridden in years. Started with two kicks but wouldn't idle since the carbs are probably gummed to hell. Looked to be in decent shape but had a flat rear tire so I haven't ridden it. I can't leave something stock so I immediately tore it down in my school parking lot. I work as a TA in the machine shop at school so this will be an ongoing winter project to keep me occupied. I'm short on cash but I have access to fun machines so we will see how it goes:

Plans:

Delete oil injection and run premix to give a clean look

Clean, paint, re-gasket and re-ring the motor

De-tab frame, sandblast, paint with appliance paint

Get rid of all the light mounts, center-stand, air-box, battery-box and the ugly seat

Strip and paint tank and headlight shroud (thinking silver with black stripes)

Fabricate carbon fiber hump seat (taking a composites class this quarter and will do this as a class project)

Clean, paint, polish everything

I kinda forgot to take a picture before I started to tear it down but it looked pretty much like this:

 

[apgamer]

Started the teardown. It's a little rusty and corroded and the previous owner did a crappy job painting the pipes with BBQ paint







Pulled the motor



here it is motor out




Pulled the whole wiring harness



Here it is stripped




Took off the side covers to strip off the nasty looking black paint. Used the stripper from Autozone. i can't believe the enviroweenies still let them sell this stuff.



Here's the motor with the cylinders and heads off once it was cleaned up





The cylinders are off getting blasted and I will most likely paint them and the side covers while leaving the main cases as they are. I really should polish the side covers but I don't think I have the patience

Here's the frame stripped and getting all the tabs cut off. Battery and air box mounts, seat mounts, tail light mounts, centerstand mounts, passenger foot pegs, ect.....




The rest of the parts are piled in the back of my SUV. I hate not having a garage or storage space.

More to come

 

[skatetheame]

Nice bike man, I'm no 2 strike guru but I think that the oil injection will be superior to the premix, just somethin you might want to look into. I know there's a few topics on here about it. I could be completely wrong tho.

 

[Dirty Dan]

You didn't over pay at all. Seriously, great looking bike. I'll be watching this build.

 

[4eyes]

I would definitely keep the oil injection. Pre-mix is a pain, unless you keep a mixed gas-can with you all the time. When I bought my R5, the first question I asked was if the oil injection worked properly.

 

[apgamer]

Okay then, I guess I will keep the oil injection. Does anyone happen to have a set of the oil injection line hose fittings that connect to the head? Not the banjo bolts but the loops that go over them and attach to the hose.

I don't want to use the stock oil tank, anyone got any creative ideas on where I can put one?

 

[Erskine]

Welcome on board!
Sweet donor bike there ..... and all the resources to make it a fun winter!
I'll be checking in on your build too.
I agree with the suggestion to keep the oil pump

 

[apgamer]

Updates:

Got the frame sandblasted and just sprayed a quick coat of primer to stop the flash rusting



Got the heads and cylinders cleaned up, re-gasketed, and put back together




Had to order gaskets from the UK


Here's the motor all put back together. I ended first painted the side covers but it looked like crap so I stripped the paint off again and polished them. i have a newfound respect for how much sanding that takes......and I wasn't even very OCD about my polish job






Started upgrading the wiring harness by getting rid of the old rectifier and running a Radio Shack one that you can get for $3.49! Added some spade connectors and plug-and-play.





I also drilled and mounted for a toggle switch on the headlight bezel. I'm going to try and run a capacitor instead of a battery since the bike's kickstart only. This switch will kill the headlight and taillight so that all available voltage can go to the ignition while starting.





This is the 12 volt source that powers both the headlight and taillight which I'm putting the switch on



Some of the wiring harness is a crazy hackjob due to the previous owner. This gem is the main line to the batter which has two fuseholders of different amperage in series along with some weird boogersoldered wires that don't go to anything.





I'm thinking about replacing these with some moped shocks. I can get them cheap and the correct size. Anyone see any reason not to? The bike only weighs like 240 lbs.





and now for the carb issue..........I'm ditching these crappy TK's. Since rebuild kits are like $45 a piece and there is now way to get larger main jets, I'm going to replace them with some Mikuni VM 20mm carbs. They are only $74 a piece and will be easier to tune once I figure out a baseline jetting. Planning on using the rapid prototyping machine to print out some intake manifold adapters so I can mount them. (hope the plastic is gas resistant)

 

[suddenlycalm]

Just wanted to throw in my .2 cents. I have one of these great little machines. If your looking at tires, i bought the michelin gazelles for around 15 bucks for the rear and 11 for the front. Wonderful riding tires. Just a suggestion.

 

[apgamer]

Thanks for the advice. Where did you buy the tires from?

 

[rjz5400]

Motorcycle superstore has them the cheapest and tubes as well. but sometimes they are on sale other places bike bandit ect....

Also good to know is that gazelles tend to be about a 1/4" bigger than the size says, meaning a 2.25 will look like any other 2.5" tire and so on. Great tires though had them on my cb125 and all my mopeds.

I thought you tore up the first picture to do all this stuff, but then i see yours is actually not perfect perfect so i guess it is cool.
Yea i would pay 400 for a non titled rd125 here in NC where you need a title.

I would however keep the center-stand, it is crucial for both tuning and maintenance like chain adjusting and oil changing, I really like center stand and get rid of the side stand, especially on such a light bike. You can clean it up, repaint it, and take off the rubber thing and narrow the feet(slightly) to make it "disappear"

 

[50gary]

I would use a set of spools and a paddock stand, the center stand is heavy and on a low HP bike every pound is important. I'm working on a two stroke Yamaha at the moment, a single, RT360 conversion as a cafe. I would like to do a pre-mix only. I'm thinking of making a laminated pocket chart for the amount of fuel to pump and then add the amount of oil to achieve correct ratio? It's sounds like a lot of work but I have other bikes for trips and longer ride etc. I've heard BT45 are also good tires for these smaller bikes.
Cheers, 50gary

 

[suddenlycalm]

Bought mine from dennis kirk. I live in iowa and they ship same day. I ordered them on weds had them by thurs night. And only cost me 6 bucks shipping.

 

[apgamer]

I would use a set of spools and a paddock stand, the center stand is heavy and on a low HP bike every pound is important. I'm working on a two stroke Yamaha at the moment, a single, RT360 conversion as a cafe. I would like to do a pre-mix only. I'm thinking of making a laminated pocket chart for the amount of fuel to pump and then add the amount of oil to achieve correct ratio? It's sounds like a lot of work but I have other bikes for trips and longer ride etc. I've heard BT45 are also good tires for these smaller bikes.
Cheers, 50gary

Yeah, that's my thinking on the center-stand. I was in the "hack everything unnecessary off with my grinder mood" so it's not going back on.

I did decide to keep the oil injection. It's a pretty well designed system and I'll find a way to mount a smaller oil tank somewhere.

 

[apgamer]

Stripped and sanded the tank. It's a little bit rusty inside so I'm going to try the "Calcium, Lime, Rust" remover from homedepot.



Chopped the rear hoop off the frame. It will go back on but will be flat with the rest of the frame


Getting started on the seat. This is the beginning of my plug






Don't worry the front is gonna get trimmed up

 

[modifiedamerican]

anxious to see the seat!

 

[Titan performance]

Very much enjoying your thread......I had one of these little beasties back in 1976. It was my second bike, following 18 months on a YB100. It was a 74 model in a similar colour to yours. The bike was a real giant killer, top speed was 80 mph, and with lively acceleration, it was enough to have close races with 4 strokes twice the capacity ! It was so low, and light, you just couldn't fall off the thing no matter how far over you cranked it.
The healthy power band gave you a real feeling of power..........fond memories.

Keep up the good work, I'm looking forward to seeing what you come up with !

 

[apgamer]

Started to bondo and sand the seat to shape:







let me know what you think about the shape

 

[montessa172]

I like to keep everything below the top of the tank, sloping forwards or back, the point in the top looks a little high to me. I like the overall shape though.

 

[apgamer]

Yeah, that's the first thing I said when I looked at it. Problem is the tank is so tiny on the bike it would make for a really short hump and I need to fit the electronics in there.