71 CT1 175 2-Stroke

Not sure this will completely be a 'cafe' when done, but it'll certainly be heavily influenced by them. Rebuilt some years back now doing a little customization... Where it sits now:










A quick concept sketch of the direction I see it going...




Input is appreciated, I'll try to keep this updated as I make changes to it!

signing up. photoshop looks great dude

Potential for a cool smaller smoker!

Something I'd like to try myself on a bike like this is replace the header with a new shape to enable the chamber to be routed underneath (plenty of clearance, unlike straight road bikes!) and exit on the left side.

If you don't do it I might be forced to but I have too much to do now!

Crazy

Rad little scoot, sir. I am on board.

There is one of those on craigslist locally and I so wanted to pick it up. (too many current projects and my wife would kill me) My first real motorcycle was the AT1 125 (your bikes little brother) That is going to be a really fun bike. Looking forward to see how it turns out.

Looks like it has some awesome potential. Can't wait to see where it goes.

I like the concept, would be a real nice around town rider. Looks like you have a Hooker exhaust.
Rider

Rider52 said:

I like the concept, would be a real nice around town rider. Looks like you have a Hooker exhaust.
Rider

Click to expand...

My 1970 125 had a hooker pipe also, good stuff. These have a much higher top speed than you might expect. My 125 topped out at over 70 mph and got there pretty quick. Of course back then I only weighed 140 pounds.

stroker crazy said:

Potential for a cool smaller smoker!

Something I'd like to try myself on a bike like this is replace the header with a new shape to enable the chamber to be routed underneath (plenty of clearance, unlike straight road bikes!) and exit on the left side.

If you don't do it I might be forced to but I have too much to do now!

Crazy

Click to expand...

Re-routing the exhaust is definitely something I'll be looking into down the road, the expansion chamber gets pretty hot on longer rides I have to be careful not to burn my leg on it when stopped. Especially because I don't plan on taking this bike off pavement very often there's no reason to have it up so high.

Rider52 said:

I like the concept, would be a real nice around town rider. Looks like you have a Hooker exhaust.
Rider

Click to expand...

Yep, Hooker header! Came with the bike when I got it, just put some fresh paint and shined the cover up a little. Would be pretty impossible to find one of these now I'm sure it got put on sometime in the 70's. It really opens the bike up in combination with the cone filter I have on it this thing rips for it's size (also makes ridiculous amounds of noise). Power band doesn't kick in until 5500 RPM with this chamber but it pulls hard in any gear to the end.

cloudrider said:

My 1970 125 had a hooker pipe also, good stuff. These have a much higher top speed than you might expect. My 125 topped out at over 70 mph and got there pretty quick. Of course back then I only weighed 140 pounds.

Click to expand...

Wow really? With stock sprocketing I hit about 65-70 at 7500 rpm right now (redline) but I have a 14 tooth front to put on when I get the chance rather than the stock 15 which should earn me a few more on the top end. Power definitely isn't an issue it'll pull all the way until it runs out of gears at the moment.

flon3y said:

Wow really? With stock sprocketing I hit about 65-70 at 7500 rpm right now (redline) but I have a 14 tooth front to put on when I get the chance rather than the stock 15 which should earn me a few more on the top end. Power definitely isn't an issue it'll pull all the way until it runs out of gears at the moment.

Click to expand...

you need to go bigger on the front for more speed, or smaller on the rear. I'm not sure how easy it would be to get a larger front sprocket but I bet the rears are pretty easy to find.I'm sure you could easily gear it to hit 75 or 80 mph and hardly notice much difference off the line.

I'm in, love these small bikes. Your photoshop is really nice and your bike is pretty clean to start with, should be a good build, good luck. I've got a couple of Yamaha dirt bike to cafe conversions going on right now so this is interesting.
Cheers, 50gary

cloudrider said:

you need to go bigger on the front for more speed, or smaller on the rear. I'm not sure how easy it would be to get a larger front sprocket but I bet the rears are pretty easy to find.I'm sure you could easily gear it to hit 75 or 80 mph and hardly notice much difference off the line.

Click to expand...

Oops, you are correct sir. I actually have a 16t just forgot since I purchased it a while ago. From my calcs this should bump my top speed up from 68 to about 75 which isn't really a huge difference.

I'm having some difficulties sourcing smaller rear sprockets however. The one on the bike now is a 45t seems like it'd be nice to get closer to the 40t range. Most websites don't list this bike so it isn't easy to look up available sprockets, does anyone have suggestions of places to look?

Ebay item number 230727589819 is a 42 tooth
Oops, that's for a '69. Competition cycle has it for the '71
http://competitioncycleusa.com/categories.php?category=JT-Rear-Sprockets/Yamaha/CT1-70%252d71

flon3y said:

Oops, you are correct sir. I actually have a 16t just forgot since I purchased it a while ago. From my calcs this should bump my top speed up from 68 to about 75 which isn't really a huge difference.

I'm having some difficulties sourcing smaller rear sprockets however. The one on the bike now is a 45t seems like it'd be nice to get closer to the 40t range. Most websites don't list this bike so it isn't easy to look up available sprockets, does anyone have suggestions of places to look?

Click to expand...

Try "Sprocket Specialists" They'll make what you need. I've used them several times before with good results.
Cheers, 50gary

Thanks a lot for the help guys. The sprocket specialist page is really helpful since you can cross reference which bikes have the same sprocket part number! Between that and JT sprockets' page I was able to find the 42t on ebay for $25 shipped not bad. It looks like the 37t is also available from some retailers so I might end up getting one of those as well depending on how the 42 goes. Combined with the 16t should buy me another 10mph on the top end and drop about 1000rpm's at freeway speeds. Maybe some gas mileage improvements as well?

I've been putting some time into it over the past few weeks while waiting for my new control cables to come. They finally came though! Got it closer to a rideable state which feels good.

Installed the new clutch, brake, and throttle cables which I had redone with black housings to clean things up some. Also shortened them a few inches to adjust for the new bars. Then I shortened up the handlebar wiring and put new coverings on it since the old grey plastic was breaking away. Also made a new bracket for the gauges as you can see in the picture and re-located the ignition switch below the tank.



Currently I am in the process of converting to 12v too! I got everything figured out and working but the headlight is drawing too much power for what the bike is producing. It turns out there are two coils in the mag, one for daytime charging and night time charging, and one for the headlight. Currently I am running everything off of the headlight coil since it was putting out the most power but am thinking I can grab power from the charging coil as well to maximize input to the battery. In the process of this I was able to run all accessories off the battery rather than directly off the coils as before.

All the gauge lights I switched over to LED's and the tail is an incandescent but I am planning to convert that to LED as well to draw less power. The headlight is a 45/55w h4 bulb which I might switch to a lower wattage bulb. Hopefully I can get this headlight to work it is MUCH brighter than the stocker



In addition I got both new front/rear sprockets on and am now running 16/42 as opposed to the stock 15/45. I only got to ride it breifly this way as the lights aren't fully functional yet but man what a difference. It feels way better and I can actually use 1st gear now. Probably part of why it feels so much better is that I finally trued and balanced the wheels which it was desperately in need of. I got the front wheel within .005" and the rear within .010".

Hopefully with all these new improvements I can get this thing into a reliable safe daily driver state, then start banging away at the bigger modifications like new forks and bodywork! Sorry for the crappy cell phone pictures I'll get my real camera out once I finish up the electrical hopefully this weekend.

looking good so far. I really want a 2 stroke about this size and era but I have to finish some other projects first though. In the mean time, I'll keep following your build with great anticipation.

I've actually been making a lot of small updates to the bike since the last post.

Ended up converting it to 12v, and installing a new 7" diamond headlight before replacing the tail light with a smaller unit. This worked out great because the new rectifier also has a regulator removing the headlight pulse at idle, as well as getting rid of the old sealed beam unit in favor of a more standard h4 bulb. Then I replaced the tail bulb, gauge back lights, neutral position light and signal light with LED units to lessen draw and provide more current to the headlight. I also installed an LED daytime running light in the headlight housing and mounted some LED license plate lights. To back all of this up I sourced a new lightweight sealed compact battery to store up some juice.

I also have polished up the case some to remove the old clear coat, and fitted a spertrapp muffler to the hooker pipe. Tarozzi rear pegs were added for the passenger since they have been getting a lot of use lately.



With two people on the bike I've been having some issues with a slipping clutch so I put in new clutch plates and some stiffer clutch springs in which drastically improved the situation but I still get slipping sometimes. I'm thinking about shimming the springs with some washers but haven't tried anything yet.

Now I'm in the process of converting to newer electric controls, a bar mounted kill switch, and adding turn signals.