I figured some of you guys may think this is a cool project and some may not. I have documented the build so far on another forum that I'm a bit more active on, but I would like to "contribute" a little more over here as well. I will copy an paste posts to get this thread up to date and then try to keep the thread updated here as I go. Here we go, the story of the neglected, bruised and beaten little tw200 fat tire converson.
I've long wanted to own a Yamaha tw200, but every time I've found one for sale, people tend to be pretty proud of them and ask what is in my opinion a little bit too much money for a long production run small CC bike. That is until when my "harmless" daily Facebook Marketplace search turned into a spur of the moment 4 Hour round trip after work to go pick this gem up. It's a 1988 model that has been robbed of a few parts by the previous owner to keep another tw200 on the road. Since it's incomplete, I don't feel too horrible about some minor customization to turn it into a neat and quirky little trail bike. The plan for the bike is to make it a fun, cheap little ride to take with me Down to Georgia When I visit the in-laws which is usually about 6 times a year. My dr650 is a blast, but after riding MisterE.'s xr200, I realized how much fun a small CC lightweight beater bike can be. I've seen pictures on and off for a few years of this red tw200 around and have always thought it has a neat look with a vintage tank and stripped down Style. At the bones it is kind of my inspiration for this build with the exception of a few things added that will make it more rideable off road including fenders and the stock airbox. I have also kicked around the idea of running another rear wheel out front. There are a few good forum posts online, and it's a fairly straightforward project which uses BW 200 Forks and triples. One of the things that has always drawn me to these little bikes is the unique and almost comically disproportionate balloon rear tire.
The rear subframe has a weird drop seat Style Bend in it which did not work well with the flat bottom vintage dirt bike seat, so after a couple hours of cutting and de tabbing the frame along with bending up some 1/8" wall 3/4" inch OD tubing, I have a subframe that fits much better. I left the frame a little long until I decide what I am doing to mount a fender and possibly a luggage rack. There will be more bracing added, but the basic shape is there.
I had made up some quick alloy spacers for the front tank mounts just to get it in place, but wanted to use rubber ones for the finished design. Surprisingly, no-one makes off the shelf mounts to adapt an atc tank to a tw200 I found these "boat plugs" at the local Menards, and the o.d. and length of the rubber part turned out to be exactly right (score), just had to drill out the middle a bit, and Walla. Also turned and welded in a threaded 10mm bung to mount the back, using rubber/ fabric washers top and bottom.
I had racked my brain on the best possible way to mount the trailer wheel to a rear spindle, and what I had planned to do was make a complete spindle from scratch, and use a bw200 wheel mount center welded to it. I figured that if it can hold up to braking and steering forces on the front of a bike, it should be able to hold up to braking and driven forces out back, at least on a 17 h.p. bike. I bought a used bw200 front hub on eBay, and it just came in. I was pleasantly surprised to find that it should work as a compete unit with a little bit of modification. The rear drum from the TW bolts directly up to the flange on the bw hub, and with an extension tube to mount a sprocket carrier and a bearing internally, it'll bolt right up. Next I need to make up a set of tabs that'll weld to the wheel and bolt up to the hub. Sometimes even a blind squirrel finds a nut.
Got a little lathe time in making the extension for the bw200 front -hub-to-rear-hub conversion. I had to turn a bit of the drum side tube of the bw hub down to make clearance for the brake plate to rest on the inner bearing race itself instead of the tube. I then turned and bored one end of a piece of heavy tube to press fit over the hub, then bored the other end to fit the bearings and seals. Yes that's right, bearings, plural. The stock tw hub had two bearings side by side on the sprocket side of the hub. I figured the engineers had a reason for this, so I'd do the same, plus it means that it'll use all standard tw200 bearings for if they ever need replaced again. I also turned a shoulder on the o.d. so ill have a square shoulder to press and weld the sprocket carrier against. I drilled a few holes to plug weld the extension onto the hub and pressed it on and welded it up. Once it was welded, I put fresh bearings in with the stock tw spacer. I checked for run- out, and all 4 tabs are within .020", and the welded tube itself is within .003". I'm not sure how close the tabs were from the factory, so I'm not gonna sweat it too much. Also, a cool dude from the dr650 facebook page sent me a stock white fender for the cost of shipping, so it matches the white front fender. (Stock rear wheel just mounted back on for some measurements)
A fairly common carb swap for the tw200's is to use a Chinese mikuni clone carb for a bw200. The early tw200 carbs are known to be fiddly and prone to angst, so I figured for $18 shipped to my door, why not. There are a few fitment issues at the outlet of the carb, in that it is to long to seat into the ridge that's cast into the intake boot. Many that do the swap just run it with the carb not completely seated and hose clamp it tightly, but I figured why not just hacksaw and file it shorter so that it fits like it "should". Even if it's just an $18 mikuni clone, it still feels weird taking a hacksaw to a brand new carb, but it fits a treat now. Ill likely have to turn an adapter to make it fit the stock airbox boot, but even that could likely be fudged a bit since I have to make new mounts for it anyways.
The bw200 rim came in the mail today, and while I knew it was wider than stock, I hadn't envisioned how much wider in my head. (Stock is 4.5" wide and the bw200 is 6" wide). No big deal though, there seems to be plenty of clearance still. Wheel has a bit of a wobble/ shimmy that I may have to get creative about straightening out. The tire spooned on easy enough again and popped on the bead pretty easily as well. All in all I'm happy with it, and I'm glad that I now have a much lighter aluminum hoop than the steel trailer one that I was originally planning on using. Plus, gold wheel ftw
It was time to clean out the garage, which also made for a good opportunity to roll the tw200 scrapheap project outside for a few progress pictures without my messy shop in the background. We are getting close. There may be snow on the ground when I get around to the first test ride, but still getting close none the less.
I know this is a mongrel bike, but I couldn't help but to cash in on the gold rear rim and paint the front to match. I gambled on a "metallic gold" rattle can, and it matched up pretty well. I used drinking straws slit down the length to mask the spokes and the old playing card trick to mask off the tire. I'm happy with how it came out, especially for a dirtbike lol[img width=770 height=433]https://images.platforum.cloud/uploads/20180908/d53b1d4bf75f0dee15937bd102c680ba.jpg[/img]
I got a little time today to finish up the rear hub. I had a copy of the stock sprocket mounting bracket water jet cut and tig welded it to the extended bw200 hub. Then I chucked it up in the lathe to true it up and left a shoulder to keep the sprocket concentric. I replaced the original sprocket nuts and bolts with the pain in the butt bend over retainers with nylon locking flange nuts as well. Also, the cool looking ribbed bw200 front drum is the same dimensionally as the stock tw200 rear drum and literally bolts on. Once I get this the rest of the bike done, everything will get blown apart for paint, rear hub included.
That brings us pretty much up to date. I have a few parts coming in to ditch the dirbike front wheel and further marry the bw200 to the tw200.
I found someone parting out a bw200 on facebook and made a deal on the forks. They'll need resealed, but the tubes are in great shape. The forks are a straight bolt on operation to the tw, even using the same bearings, so not much magic to show there. The front tire looks shorter than it is probably due to the width, but in reality it is only an inch shorter than the stock tw200 front tire.
No big update, but I did rearrange the garage and rolled the tw out for a couple shots without my cluttered garage in the background. She's definitely a weirdo. I'm thinking about running a blaster shock out back to bring the rear end back up again.
I spent a shameful amount of time this evening figuring out how to and implementing a way to use a tw200 front brake cable on a set of bw200 forks/ brakes. The tw cable is much cheaper and easier to find than the bw cable, plus in the happenstance that this fat front tire handles like do do, it'll make the swap back to the tw front end even easier. I ended up turning an adapter up on the old south bend lathe, including some jakey y axis broaching for the slot. Also, after trying to figure out the best option for a front fender, I bit the bullet and bought a decent used bw200 one. Should be here along with the tank on Monday.
I got the fender and a cool patina Honda atc tank in the mail today. Happy with how they look on the bike, unhappy with the hole in the tank that was advertised as not having any holes. Ebay seller is being a tool about it too, unfortunately. Oh well, at least it'll look cool once fixed. I am planning to just clear coat the Honda green paint and leaving it alone. That'll make peoples head scratch even more with this stupid thing lol