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mtothef 03-18-2012 08:48 AM

The saddest RD350 in the world
I swear, I had no intention of doing this. The last two "it's raining and I'm getting a bit twitchy" projects proved ALL the old adages about old motorcycles and flushing money down the toilet, but they also served notice that I am a hopeless sucker for just about anything Yamaha cobbled together in the 70s and 80s:

giant time and money hole #1

and giant time and money hole #2

It should be noted that both the abovementioned money holes are, as is usually the case with me and internal combustion things, unfinished. Little things like brake lights and horns and clacky exhaust valves, but they are done enough to run, and the hunger for something new has been chewing at me for a long time now. And that hunger has been entirely two-stroke in nature.

So, just as the search for a Bultaco Metralla had raised nothing but frustration and questions about my deeper level of sanity, and the local sources for old DT or RT Yamahas (remember, I have a weakness) to turn into lightweight canyon rippers was proving dry as the Arizona desert, completely by chance this wee beast followed me home the other day:

A 1975 RD350B, minus gauges, seat, sidepanel, and any sort of paperwork. Including the dubious merit of RD400 cast boat anchors, err, wheels and brakes, and a pair of expansion chambers that can only charitably be described as "crude." But, the bike was free, or close to it. How bad could it get, right?

fastdadio 03-18-2012 09:05 AM

Oh man, I feel your pain. It's like taking that first shot of tequila. You know your gonna regret it, but it's going to be a fun ride all the way down.

mtothef 03-18-2012 09:21 AM

So, we begin digging...
How bad could it get? Pretty bad.

The bike turned over, and as I would discover later, not one of the bolts I touched was frozen, which is a rare and beautiful discovery when stripping old shitpiles. Oops, scratch that. ONE bolt frozen, the barrel end for the autolube cable where it enters the crankcase to pull the oil pump. Other than that, relatively plain sailing. Let the deconstruction begin:

"Dude, you're gonna be pretty surprised and stoked by this. It was kept inside the whole time it's been sitting! It looks rough, but it's in much better condition than it looks..." So it goes with the lines of bullshit people use when trying to somehow polish what is very evidently a turd. Probably should just say, "Look, it's a turd. You know it, I know it. But it's not costing you anything yet, and you are dumb enough to see some nugget of value hidden somewhere in all that turd, so here, take it away." In this case, we will assume that the bike was stored inside an arboretum, with all the indoor oak trees.

That'll buff right out...

Yeah, so will that.

Nothing but the finest materials and most skilled handiwork were used in this bold leap into the disc brake future...

We will assume this is the secret ignition bypass switch. Hidden under the tank, where nobody would think to look. That way, bike thieves would be thwarted in their efforts to make off with this treasure. Seriously, why the fuck is there a switch here?

Okay, first spot of good news, aside from the bolts all turning. The tank is only modestly dented, and there is barely a hint of rust inside it. I'm assuming that the sheen of jellied old premix leaking out of the tank vents acted as a corrosion inhibitor, but seriously, the tank looks good inside.

So, the many cancers are removed and placed in a pile:

the patient's heart is made ready for what will surely be a very invasive surgery:

and the corpse is stripped until only the laughing bones remain:

And now the questions begin. No way am I going to try and return this to stock. Too much missing, so much of what is present is very very bad. So, what I want to do is end up with a lightweight, stripped down little beast that is quicker than stock but won't continually try to eat itself (I have an Aprilia for that), that makes me grin when it hits the powerband, and that can be used to good effect on the twisty roads that are everywhere here. But, this is my first RD. I really don't know jack about them, other than the fact that they are well loved and that there sure does seem to be a mountain of parts options out there for them. For now, the tentative build is looking as follows:

Crank rebuild, balance

Mellow port job, rebore

Squish band work on the head

Bearings and seals as needed

New chambers

Y-boot intake and single K&N filter

While that is taking place, gonna cut some brackets off the frame, blast it and powdercoat it black. Might invest in a fancy swingarm. I've got a couple pairs of shocks laying around that are an inch longer. The entire front end looks like a horror movie, not sure what to do about that.

Gonna need some spoke wheels, probably go back to a drum rear brake. Rearsets. Got an Omar's seat somewhere that looks like it'll fit. End result I am hoping will look a bit skeletal, upright, somewhere between stock street and cafe. The proliferation of brat style bikes has me real bummed out, so I want this to look a bit more spindly and functional. I want it to work that way too.

Questions, for the pro/con peanut gallery:

Premix, or rebuild the autolube?

Electronic ignition, worth it? (I like the possibility of ditching battery for weight reasons alone)

What chambers work best, assuming this is going to be more a mid-range ripper than an imitation TZ?

What hubs fit old RDs, front and rear?

Dear god, what do I do about the front end?

Here we go again!

mtothef 03-18-2012 09:22 AM


Originally Posted by fastdadio (Post 18244136)
Oh man, I feel your pain. It's like taking that first shot of tequila. You know your gonna regret it, but it's going to be a fun ride all the way down.


mtothef 03-19-2012 07:32 AM

Digging in...
Caked in oxidization and coated in leaves and spiderwebs, the old girl wasn't giving me much reason for optimism about the state of things inside the motor. But, there was pretty decent compression and no funny noises when turning it over, so, hard to tell. Pulling the heads and barrels off revealed some nice surprises:

Obviously someone had done some work not too long before parking it. Bores looked relatively clean as well, hardly any blow-by around the rings, plugs were clean. Top end and rod bearings felt okay to the touch, even the main bearings seemed to be rolling smoothly. She's coming apart anyway, but it sure feels and looks like someone tried to give the old girl some love once upon a distant past.

Piston says 50 on top of it. Does this mean it's on the second oversize? Gonna have to get a manual here one of these days...:

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