So a long time ago in a mindset far far away . . . I was surfing E-bay. Had a credit card. Probably had something to drink. I ran across an auction for a 1970 AT1 125 that was the spitting image of my first Yamaha Enduro. I had originally purchased it in 1973-74 from a friend's father and it was in immaculate condition. The infamous little old man who only rode it to church on nice days! It was the bike I got my first street license endorsement on. The first bike I rode on the freeway with a trail sprocket and knobby on. Too many good memories to say no. So I bought the darned thing in about 2004 and brought it home.








Pretty complete overall, and it ran. The tank badges were missing (and I was not aware of how hard they were to find back then!), it rattled, needed tires seat cover, general tlc. But it made me smile

The search began for parts and other crazy folks who liked these old bikes.

So the bike sat there - kind of mocking me - in the garage. I worked out the title paperwork so I could get a tag on it. Then I located a seat cover from NW Vintage parts - the beginning of a long and prosperous relationship . . . for them! Good folks who really treated me very well and continue to be good friends of the site.

I scoured Ebay and found a brocure of what it should look like:



Then I ordered up some Cheng Shen repop universal tires, a bit larger than stock but I liked the look.

I was able to ride the bike about town, and really began to relish the smiles and "thumbs up" the bike would generate. I even found some "fake" tank badges to make it look at least presentable.

Re-doing the seat was one of the first orders of business, and probably the biggest visual improvement on the bike. This has repeated itself many bikes over, with a ripped seat making the curb appeal of a bike simply change overnight!



Of course, just re-doing the seat, and thinking now things are great! I began to ride the bike without really doing too much more. Big mistake.

A short in the wiring led to a complete melt down of the harness. Toasted my regulator. The bike got rolled to the back of the garage to be forsaken for more than a year as I began prep on my Trans America Trail ride DT400.

More to come . . .

Great story. Looking forward to the "more to come."

Very cool. I have a couple of these bikes. I like the color, its the opposite coloring of the 1970 RT1. I know some people only like the bigger bore bikes but I like all of them. The little bikes are lighter and more agile on some trails. Captain Dave knows what I am talking about. . I plan to do the same mod you did. A 175 top end put on a 125.
I am looking forward to seeing this build.

For those of you new to this tale, the bike was purchased about 3 years ago late one night on E-bay in a sick attempt to re-acquire the bike upon which I had obtained my very first (and only) motorcycle endorsement, in 1974! The bike was located about an hour and a half from me, so I had to have it. I had not yet been diagnosed with Enduroholism. But then again, they hadn’t come out with the new DSM-5 manual for diagnosing such disorders at that time . . .

Here is the bike I brought home:

Then, of course, the TAT DT400 Bike came into being and the planning and prep for the Vintage Trans America Trail (documented elsewhere) began, and this old gal got pushed to the side of the garage as the "other woman" usurped its rightful place.....

Well - as luck would have it, during the TAT bike build, I was also looking for needed parts for the AT1. I sourced a NOS wiring harness from Northwest Vintage, and a NOS regulator from Old Part Shop in Singapore. Somewhere along the line I found a pair of NOS key switches (the old one worked, but was a bit rusty).

One day, while waiting for paint to dry on the TAT bike, I moved a box and saw the old gal sitting there in the back corner of the garage, so decided to replace the wiring harness and regulator and get it running so I could have something to toy around with.

At the time I purchased the bike, the missing tank badges did not bother me too much. Little did I know the trials and tribulations I would go through on just that one little pair of details!

These ended up being like Hen’s teeth. This was before the quality repops became available.

One night I was able to find a nice set of NOS on Ebay for a price that was too low to disclose. It was about 11:00 p.m. and it was a buy it now. I happened onto the listing less than 10 minutes after it was listed, so of course I bit!

Yep - NOS original badges still in their factory wrappers!

After getting most of the little problems fixed (very little cosmetics) and nearly losing my mind trying to fix the electrical starting and charging system, with the help of an old school mechanic and many friends, the bike became a runner and I got to play around with it some. I got some tank badges made of stainless with a black overlay, which at least filled in the ovals on the tank. The NOS badges are locked in the safe until I do a full-on restoration of this bike.

So as more and more bits and pieces came off the frame (necessary to get to the wiring harness for proper replacement, at some point you arrive here:

A crucial decision was made. Gee - While I'm in here this far.........

When you replace the wiring harness, you have so much stuff off the bike that to get to this point, it is only about an hour or so more wrenching. So what could I do? You get to the point it is closer to strip the bike down to the frame and do all that stuff you always were gonna do . . .

Of course, it seemed a good time to get the annoying rattle in the top end fixed, so I acquired a new piston, then, in a moment of ADHD, I lost focus and decided it would be neat to make it into a 175! :P

A new piston and head was acquired courtesy of Dave Rymal in Paso Robles, California. A piston was found on E-bay, and sent off with the 400 piston for ceramic and teflon coating at SwainTech .

Before:



After:



Sure it is overkill, but what could I do? There was space in the box! (Note the rare, special edition Yama-Phone on the table . . .)

While those items were in New York, getting a pretty grey protective coating applied, I started a discussion with Enduronut, (a really big mistake). We determined that the 175 cylinder would work so much better with a mild port job, so when the piston got back home, it went on another little trip to South Dakota . . .

Just a little testimonial for EN's work. This stuff is amazing. If I were a Rapper, I would probably have the cylinder hanging around my neck! I really hated to take it off my desk and put it on the bike!


More to come!

_

Another shot of the Enduronut prepped cylinder:

Ports reworked and polished, the head shaved and polished, piston slightly reworked for better performance, and gosh, wouldn't it be a shame to dump all that fresh new oily exhaust into a nasty old stock pipe? EN hooked me up with a fresh in the box, NOS Torque Engineering Chamber which will eventually find a home on the bike if it is not too loud.

This is what goes into a 125-175 conversion such as this:

Head, cylinder, piston, piston pin, circlips, rings, head and base gaskets, exhaust gasket, carb gasket, and piston pin bearing (it is different on the 175 than what is on the 125). I ended up not needing any of the round seals, but will replace them if need be later.

Now the teasers - The assembly has started. I am anticipating completion in about a week, depending on my free time. All the parts are here. I have left the oil and fuel tanks un-painted (i.e. left them stock), but anticipate that may happen later.

The motor went together nicely:

NOS clutch cable installed, fresh paint on the stator side covers (the other side was fine). I used Duplicolor Caliper Paint which ended up being almost a perfect match for the engine covers. Hopefully it will be more durable than most others. The little yellow hose behind the cylinder is a new crankcase vent hose.

To see just how dramatically the bike is changing, here is a before and after picture of the voltage regulator area.

Before:

After:

You can see the nice gold-toned plated NOS voltage regulator direct from Singapore!

Renthal (non-o-ring) gold chain and new factory sprockets were also added.

Below is a picture of the cylinder that Enduronut ported ....... as you can plainly see from the casting, this engine/cylinder is obviously a 125 ..... and not a 175!

That is Enduronuts hand, carefully replilcating the 123cc casting. by hand, on the base of the newly ported 175 cylinder . . .

The power of the Dark Side is great, and only true Enduroholics can be trusted to use it for good . . .

I got my carb back, after a full on dip in the cleaner, it is nice enough to eat out of. I changed out the main jet (Richer) for break in and installed it.

I also got the taillight rebuilt, new stainless socket heads for all mounting points and the new grey cable sheathing from Vintage Connections .

Other than blinkers, which I waited to install until after I got the bike all going (I didn't want to add any possible electrical issues until it was running right and all the stock stuff worked) the back of the bike was mostly done. I also needed to add the rear rack, but that would happen with the blinkers to minimize the possibility of scratching things.

I was working in some really close quarters on this thing and it had been pouring down rain for a few days, so the only picture of the whole bike I could get was two photo's stitched together. It makes the bike look somewhat out of proportion, but it will give you an idea of how things were coming along.


More soon!

_

OK - another day, another post.

The controls were next. Handlebars, levers, mirror mounts, grips, cables in place. I was able to get outside between showers and get a few pics showing the progress a bit better.



The lever ounts were stock and some modified mirror mounts were added, as I really hate the original style which tend not to stay put well. I also adapted some "dogleg" levers to work on the bike. The brake lever being a challenge, as the lever did not include a little nub to operate the early style brake switch which mounts under the lever.





I took a stock lever and laid it next to the dogleg to locate the spot, then drilled a small hole, and inserted a roll pin to operate the switch. Cheap and easy, and allows the later levers.








The rubber lever covers were located in a NOS bin of aftermarket stuff at a place called Bent Bike in Lynnwood, WA. Nice to keep the lever clean in really bad conditions. The bike is also using the repopped grips from the Motobiker store on Ebay . The ONLY grips to make the bikes like original.

I was next able to get it off the stand and test the shocks, both the front and the rear feel really nice.



I used 7.5 lbs oil in the fronts and the Showa shocks on the rear are set at their softest. I may need to increase both of those after riding it a bit. The steering is a lot smoother now, after cleaning and re greasing the steering head. This bike also has a factory steering damper designed for the DT series which is a direct bolt on! These really help on a bike which is mostly street ridden. Fits up under the steering head.

I was able to locate a couple of NOS factory paper air filters so the bike got a new breather!


I also spoke earlier of the NOS Torque Pipe that I got from forum member Enduronut. I was not ready to install it when I wrote this originally, but I had to get it out of it's hermetically sealed case and test fit it......

As you can see - it feels right at home!

The tires are Chen Shin. 4.00-18 on the rear and 3.50-18 on the front. They are copies of the old Dunlops and actually ride out pretty well. I will find a set of streetable knobbies in similar sizes for the bike, 'Cuz I really like the look of them. I have an extra set of wheels I could use for them too.

I will still be installing the stock pipe for break-in as we discussed. I just had to see what the chamber looked like on the bike! I really couldn't be happier with it! [:-!]

Since I planned on riding this bike on the street, I later did a short test on the comparative noise levels of the factory VS the Torque Engineering pipe. I live in a town where the police are not too strict on such things, but it is interesting. NOTE: The pipe in the test has an aftermarket spark arrestor which will be documented later in the thread.



More on the way!

I'm currently converting a AT2 125 to a 175 as well. Can't wait to a have an electric start 175. Would love to find an after market pipe for it too

Your project is looking awesome. I'm envious of that nice pipe. My CT1 pipe is getting the works as we speak.

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