Yamaha AT1 Budget Street Tracker

Discussion in '2 smokers' started by Kiba, Dec 24, 2013.

  1. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    My new-to-me, titled project:

    [​IMG]
    [​IMG]

    Delivered by a fellow inmate today, christmas eve 2013. Maybe I can get it done by morning and stick it under the tree.
    [​IMG]
    ...or not. :D

    It's a titled, non-running 1969 AT-1E, yep, the one with 12v electrics, e-start and that funny gen/starter thing on the crank.

    [​IMG]

    I love the lines on the bike, and its mechanical simplicity compared to even my big thumper. I'll have to tear down the bike to chase what is likely an electrical gremlin anyway, so I figured I'd go for a simple restomod as well.

    ****DISCLAIMER: The direction of the project has changed. Ignore the eggnog-fueled brainstorming session below, unless you like that sort of thing.


    I would like to do a basic street-tracker/street scrambler look in the cosmetic department. Basically, a high front fender or small universal low front fender, lower bars, bar end mirrors, etc.

    In the performance department, I'm having a hard time finding decent street tires for 18" rims, of which the AT has two.

    The mechanical drum at the front is tiny enough to inspire some dread too, even at low speed.

    The stock gearing is very low. Although it is a 125, I think I could go a little higher and still cope with some off-road work.

    All of these factors have me considering a wheel swap, but I have no idea what wheels would fit this bike. Even a front wheel swap to a 19" and maybe a rear rim swap and respoke would make a difference. A front hydraulic disc, even an old outmoded one, would be nice. I have no problem swapping the forks too if necessary, or even the triples and bearings. I was thinking a YZ125, maybe? There are plenty of local CL w/o title or running, but with probably unbent, skinny forks and little front wheels with discs.

    From what I understand, the CT-1 shared a bottom end with the AT-1 and they were essentially the same engine with a bigger piston, cylinder and head (175 vs 125). I'd love to get a decent piston/ring set and pop on a 175 cylinder/head for some more pep.

    The stock rear shocks are soft- too soft- and a bit low even for me.

    Last but not least, the bike came stock with both a 12v lighting system and no turn signals, so I see potential for a plug-in solution to crappy lighting on this little bike. LED taillight bulb to take load off the gen, than a 35W or better modern halogen.

    My mind's eye sees a small, very light little street scrambler with a small rack for groceries/camping stuff, backroad cruising ability and retaining some competence off-road (at the very least, not complaining about a rutty gravel road).

    I'm just spitballin' the specifics, but that's my general idea. Suggestions on the various parts swaps? I haven't been able to find much on this bike, and if anyone owns one and might have some information, I'd appreciate it :ear


    Also, in case this ruffles some feathers-
    I wouldn't usually do this kind of modification on a bike this old. But someone- the previous, previous owner- seriously hurt the bike's value for OEM restoration by repainting the tank, a few frame bits, and exhaust, and did a few other miscellaneous mods that, when added together, make it not worth the time and money to bring back to OEM shape. I am also intent on doing the build properly, selling rather than discarding the OEM bits I don't use, etc.

    More pics to follow.
    #1
  2. Foot dragger

    Foot dragger singletracker

    Joined:
    Dec 27, 2006
    Oddometer:
    14,552
    Location:
    chico,just below rag dump(nor-cal)
    Dang,that little thing is still awful clean and oem stock looking to mod it up.
    But I guess they made a lot of them. Back in olden days when I raced shorttrack those bikes were known for handling like a cross between a shopping cart and a flexy flier wagon. short wheelbase,skinny forks and frame,twitchy is a kind word. But guys rode em anyway.
    #2
  3. bykpimp

    bykpimp Live and let ride

    Joined:
    Oct 18, 2006
    Oddometer:
    1,410
    Location:
    Santa Cruz Ca
    What a sweetheart of a bike. Why on Gods green earth are you even considering hacking it up? Bring it back and use it for it's intended purpose. I know it's your bike and you can do as you like.
    #3
  4. Mr. Carts

    Mr. Carts Been here awhile

    Joined:
    Jan 14, 2010
    Oddometer:
    411
    Location:
    Cahuilla Mountian
    I did the 175c conversion on one that stuck a piston years ago.

    I went down to the dealer a paid I think it was under $75 for the barrel and piston, I cant remember if I reused the stock head or put a 175 head on it.
    #4
  5. Scootern29

    Scootern29 Been here awhile

    Joined:
    Sep 4, 2012
    Oddometer:
    931
    Location:
    In the hot, hot, dezert
    I'm with bykpimp on this. That bike looks very close to original, and it would be a shame to hack it. There is a big following for old Yamaha enduro's like yours. I just picked up a 175 that is no where near yours condition wise and I would not even consider changing it from it's intended purpose. If you are going to build a street tracker, use a bike that is bigger cc wise.

    These guys on this forum www.yamahaenduro.ocm have a wealth of knowledge on these bikes and live, eat, and breath Yamaha enduro's.

    My two cents
    #5
  6. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    Okay, okay...

    I may have had a bit too much eggnog last night. :D

    I'll start over.

    I finished the teardown today, down to almost a bare frame. I found myself enjoying the utter simplicity of the thing and I started to desire to change it less as time went on.

    However, I still have some needs that will require modification. I want to change as little as possible, but where I need to change something for safety or ergo, I will. If I have any spares from the bike, I will post them for sale (or give them) here on ADV to other owners before ebaying.

    I have three main concerns:

    1. Lighting. Mainly the headlight. There are no indicators on this bike from the factory, so the electrical system doesn't have to put up with a ton of load. But the 12V, 35W H4 bulb on my XT600 is just bright enough for safe riding at night. I doubt the stock 12V bulb on this machine is.

    However, the bulb on this bike is not a sealed beam!:clap

    I don't need to change anything visible on this bike to get better lighting. I need some assistance though, on how many watts this thing can tolerate without straining the generator. 35W on an H4 or similar would be fine.

    2. Brakes. My first bike was a KE100 with a similar tiny, mechanical drum on the front, and it braked like crap. I would not feel safe riding it on the street here because my emergency stop distance would be so long. I haven't used the brakes on this bike, but given that its the exact same size and type I'm not enthused. I also don't only ride in the sunshine, so when the weather is bad I can't get instant washout or fade.

    Please, old bike gurus, tell me the secrets of riding a bike with terrible brakes. Or how to improve them mechanically, even a little. :ear

    3. I need this bike to cruise at about 40-45, and hit around 60-65 top, for safe use in Houston backroads. This seems like a reasonable goal for a 125 smoker with stock gearing. My unmodified KE100 could do it. Please tell me if otherwise.

    I may hold off on the go-faster head swap for now, since it has compression. But I won't rule it out for the future since it's period correct.
    #6
  7. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    I've looked at the specs for the AT1 and it seems that my performance goals are about what the stock bike should be able to do.

    The Clymer lists the stock gearing as 16/45, and the wikipedia page suggests the top speed is about 60-65.

    The lighting issue remains a problem since I can't seem to find anything on what wattage of bulb is acceptable for the little generator. But it will only involve swapping bulbs, since its not a sealed beam.
    #7
  8. mtothef

    mtothef Been here awhile

    Joined:
    Dec 23, 2006
    Oddometer:
    411
    Location:
    santa cruz, ca...
    so true... i remember being about 13 and watching my buddy hauling ass on an at1mx down a flat, almost perfectly smooth straightaway. he hit what was basically a ripple in the dirt and proceeded to go into this tankslapper to ragdoll to yardsale endo. it was spectacular. once we determined he wasn't too broken, we all went looking for the huge rock that must have caused such a violent crash. nothing. just a little dip in the dirt. grim handling little beasts...
    #8
  9. plugeye

    plugeye dreamer

    Joined:
    May 11, 2007
    Oddometer:
    5,324
    Location:
    Garland, Texas
    always use engine braking/ downshifting way before braking.
    on a 2-stroke it might not be enough, but it's how i ride my 4-stoke.

    service the brakes & get them working well.
    #9
  10. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    I did have a question on that. I was thinking of engine braking but remembered that it wasn't supposed to be good on a 2-stroke due to oil starvation.

    However, is it different if it has oil injection? According to the Clymer the injector pump on the AT/CT bikes actually lubes the bearings and various other bits that cannot be lubed with premix in this motor, hence the need to have the injector setup.

    Does this mean I can engine brake this bike like I do a regular four-stroke engine without grenading it? If so I have no worries about the brakes. I just don't want to ride around with no engine brake and primitive drums.
    #10
  11. bykpimp

    bykpimp Live and let ride

    Joined:
    Oct 18, 2006
    Oddometer:
    1,410
    Location:
    Santa Cruz Ca
    You ride it accordingly. Ever drive an old split window VW Bus? You're an active participant. You plan your hills and stoping in advance. Don't over ride your tires or your brakes. They also had this wacky device for smokers in the ole days. In fact I had one a an Yamaha MX100, 360 and have one on my 74 SC500 which is still on original tires. It's called a compression release. Works very much like Jake brakes on big riggs. Engine breaking on smokers is nest to noexistant, anyone that's ever ridden one will tell you the same. I also think you're being optimistic if you think you're gonna cruise down the road at 60 mph on the thing. You may, just not for long......:lol3

    My plated 07 WR450 with every bit of gearing available will barely do 60 down the road without reving it's nutz off!
    #11
  12. Foot dragger

    Foot dragger singletracker

    Joined:
    Dec 27, 2006
    Oddometer:
    14,552
    Location:
    chico,just below rag dump(nor-cal)
    You'll find now that 1971 has come and gone some time ago,finding a good 175 cylinder can be done but not quite so easy.
    Yamaha DID make cubic tons of these things at one time.

    The trick would be finding a Noguchi 175 top end,guys ran those at the local shorttrack and stuck the engine in a Champion frame,light and ungodly fast compared to my 200 Bultaco at the time.
    #12
  13. Foot dragger

    Foot dragger singletracker

    Joined:
    Dec 27, 2006
    Oddometer:
    14,552
    Location:
    chico,just below rag dump(nor-cal)
    Oh Yeah,a compression release would add much to the drama of riding an AT1 around town,I think they can be found on ebay,the noise and engine braking provided are well worth it! The AT1 cylinder head should have two spark plug holes,one with a spark plug and one with just a plug,compression release goes there.

    Rev a two stroke to peak revs,hit the C release,its great fun and addicting.
    An original Gyt-Kit pipe would also add to the fun,neighbors would then hate you and the bike equally.:rofl
    #13
  14. Andyinhilo

    Andyinhilo Long timer

    Joined:
    May 16, 2008
    Oddometer:
    1,773
    Location:
    Hilo, Hawaii
    My step-mother had one of these as her first motorcycle, and I rode it a bit. It is within the capabilities of what you want to do.

    The generator should be able to handle a 35W light with no trouble, just make sure that you check the brushes for wear occasionally.

    You can use the engine braking with no worries, but as noted, there isn't too much there.

    As for the drum brakes, make sure the cables and levers are in good shape, and adjusted properly, and the lever on the brake itself is installed correctly. If the drum and shoes are in good condition and clean, it should stop OK. Not great, but OK. Planning ahead as much as you can will enhance your safety experience.
    #14
  15. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    I'm familiar with the nature of 2-stroke engine braking, but at least it does something. On my KE, the oil injector didn't function well, so I ran premix and was afraid to use the engine brake for too long because of oil starvation.

    Gearing counts too. That same ratty KE could do 60, and cruised at around 45-50 pretty comfortably. And it had 25ccs less and a much worse mechanic servicing it at the time :D

    As for compression release, well, I do have the original assembly...

    That's what's weird to me. I know these were made in large numbers yet there doesn't seem to be an abundance of parts bikes/etc for them. I was hoping to build a little stable of them: one stockish, one MX, one cafe-type, etc.

    I really should do the 175 top end while I have it apart. Do you remember whether the 125 head was the same or did you have to swap that too?

    Thanks for the help. In your experience, how bad was the Yamahop in corners?
    #15
  16. plugeye

    plugeye dreamer

    Joined:
    May 11, 2007
    Oddometer:
    5,324
    Location:
    Garland, Texas
    +2
    wrung-out maybe 50
    #16
  17. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    Jeez guys... my KE100 would do an (indicated) 65mph, flat out in fifth. With 25 fewer ccs, questionable maintenance history and running 25:1 premix.

    Because of speedometer inaccuracy I figure the real speed was around 60.

    But I could cruise in top gear pretty comfortably at an indicated 55mph, which was probably about 50 in real speed.

    Why couldn't this bike do the same? It has a displacement advantage, better maintenance, functional oil injection, and tires that aren't knobbies.

    I'm all ears, but what's the difference? :ear
    #17
  18. Foot dragger

    Foot dragger singletracker

    Joined:
    Dec 27, 2006
    Oddometer:
    14,552
    Location:
    chico,just below rag dump(nor-cal)
    AT1's are ratty little bikes designed in the late 60's,to put it bluntly.
    The noises they make going down the road would cause any sympathetic person to slow down. They are good for putting around,going fishing,cruising around town. They dont make much power is a kind way of saying it.

    Even my old 1972 250 Yamaha Enduro wasnt fond of hiway cruising at much speed. I blew it up at least 3 times in 30,000 miles or so and still didnt kill it completely,just kept cleaning it out and boring it again.
    Ill handling knee breaker of a bike.
    #18
  19. Kiba

    Kiba Dances With Huskies

    Joined:
    Nov 8, 2013
    Oddometer:
    2,662
    Location:
    Houston, Motorcycle Purgatory
    footdragger, since you have some experience with these bikes, can you remember how complex the CT head swap was? A guy on ebay has the jug and piston and it would be nice if it were that simple. But if not, there's the head, pipe, carb jetting- and whether the bottom end is really the same. Do you remember whether the jet, head, etc had to be changed or was it a straight shot w/ jug and piston?

    I have a spare parts motor coming in so I'm thinking, "Why not?" :lol3
    #19
  20. Reverend12

    Reverend12 Well there it is..

    Joined:
    Nov 21, 2008
    Oddometer:
    1,517
    Location:
    Classified
    My first Bike, That bike is really nice, don't hack it.
    #20