Swamp Donkey 2.0 Fat Tire Bikes Make the Rockin World Go Round'

[Tim]

I don't think that rim is going to deflect much if at all. The big phat soft tire on that thing is going to do all the flexing. Run it! Looks like fine German engineering.

 

[irk miller]

I don't think that rim is going to deflect much if at all. The big phat soft tire on that thing is going to do all the flexing. Run it! Looks like fine German engineering.

You'd be surprised. I've experienced it first hand. Not to the point of being a huge deal, but I lost a nice groove of powder coat in a 12" rim running bias-ply street drag tires, which have no side load resistance. My lower shock mount clears the inside of the rim about 5mm, but still wore the groove in the rim and made a flat spot on the screw head.

 

[Hurco550]

I think there is just as much of a chance of fork and axle Flex /twist that might possibly cause some issues. Either way I think I have plenty of option to grind some clearance on the caliper, so it shouldn't be much of an issue.

 

[Hurco550]

Still plugging away. Right now i'm mostly designing parts for the fork conversion and swing arm. Through the facebook tw200 group, I was able to borrow a tw200 swingarm to steal some dimensions from. Also got the 250mm rotor in, so I can make the adapter and finish up the front wheel spacers and bushings.

 

[Popeye SXM]

I love this thing
Sorry for the late reply. I was determined not to use a jack shaft. I narrowed the Honda hub (not difficult as made of steel) and used a 3/4'' offset drive sprocket to line up the chain. I used the front part of the DZR swing arm with the arms from a KX100 Now fitted with custom made triple clamps from Cognito moto, lovely

 

[irk miller]

That's good stuff right there.

 

[Hurco550]

I love this thing
Sorry for the late reply. I was determined not to use a jack shaft. I narrowed the Honda hub (not difficult as made of steel) and used a 3/4'' offset drive sprocket to line up the chain. I used the front part of the DZR swing arm with the arms from a KX100 Now fitted with custom made triple clamps from Cognito moto, lovely

Awesome man, I love it! Thanks for the info. I think i will be running a wider rear tire and therefor will probably still have to use a jack shaft, but it wont be as wide as the bw200 swinger. I hadn't realized how wide they actually were until I saw the one in front of me on this bw200.

I am making my own triple clamps, and am planning on using a similar design to the XFR kit for the yz450. They will be out of 1" thick (25mm) 6061. I am assuming that they will be adequate, but I am a bit concerned about fork twist, as the stock RMZ clamps are much taller for a wider clamping area, and have two bolts per clamp. I may also be over thinking it, as these forks will be way stiffer in any setup than the stock bw200 noodles woulda been. Just kinda curious what yours are designed like from cognito?

 

[SONICJK]

Any particular reason for using 1" 6061?
Most triples are at least 1.25-1.5".

No expert opinion here, but if I were making them from scratch I would step up a bit to thicker material and use 2 m8 clamping bolts.
Unless you just have the 1" material sitting around for free in which case I'd go that direction lol

 

[Tim]

The bottom is where you need the strength, if my mind is working properly Monday morning. That's where all the real force is applied.

My BMW R75/6 has a plate metal top tree, for example. No clamping at all at the top - it is secured to the top of the fork tubes by the caps.

I think that may be why on so many bikes (my XS650, my tiny Honda ST90) the lower tree is cast steel and the top is aluminum, full of holes for gauge mounts etc.

I'd go thicker on the bottom tree and leave the top.

 

[Hurco550]

Any particular reason for using 1" 6061?
Most triples are at least 1.25-1.5".

No expert opinion here, but if I were making them from scratch I would step up a bit to thicker material and use 2 m8 clamping bolts.
Unless you just have the 1" material sitting around for free in which case I'd go that direction lol

Bingo lol thats actually one of several reasons. The others are the fact that I don't have the access to the CNC equipment that I used to. If i used 1.5 thick material, it would be uber heavy as these clamps will be almost 14.5" wide outside to outside. I have access to a waterjet and a bridgeport with a boring head, the 1" offers the best path to complete. Water jet the profile, bore the holes to the finish size and call it licked. The other reason is that the kit that they are selling is 1" with single pinch bolts. My quandry comes from the fact that just because someone sells it, doesn't mean its right lol

 

[Popeye SXM]

I am building mine to a boulevard cruiser so no mx! I am running a 23 x 8.0 (195/80) x 11 tyres. The chain my rub under extreme right hand corners, I am not sure how much the side wall will move. 3/4 inch was all i could get away with on the drive sprocket.
My triples are standard Cognito design (very nice) with 1'' top and 1 3/8'' bottom. I built plywood mock ups then when I was happy I sent Cognito the dims

 

[Hurco550]

I am building mine to a boulevard cruiser so no mx! I am running a 23 x 8.0 (195/80) x 11 tyres. The chain my rub under extreme right hand corners, I am not sure how much the side wall will move. 3/4 inch was all i could get away with on the drive sprocket.
My triples are standard Cognito design (very nice) with 1'' top and 1 3/8'' bottom. I built plywood mock ups then when I was happy I sent Cognito the dims

Good info as always. I'm not planning on doing any real MX, but it will be subjected to some pretty rough single track and trail riding, so i cant have them coming loose. I'm looking at running a 26 or 27 x 9.0 r12 up front and a 24 x 10 or 11 r11 out back.

 

[Tim]

Make it fancy and double up the bottom tree. Space them apart by an inch or so. A true 'Triple' tree (why on earth are they called triple trees anyhow - the 2 forks and the stem?)

 

[Hurco550]

Make it fancy and double up the bottom tree. Space them apart by an inch or so. A true 'Triple' tree (why on earth are they called triple trees anyhow - the 2 forks and the stem?)

Funny, a thought similar to that crossed my mind, and in a manner, may come into effect.

Also, always wondered the same on the name. I assumed it had something to do with the stem and 2 forks, but all google can tell me is further speculation lol

 

[Tim]

Apparently it might be from the Tyburn Tree / Gallows. Triple Tree comes from the triangular shape realized from the forks leading in front of the steering stem. So it might all be related to geometry, which would make a lot of sense.

I guess this is what people did for fun before motorcycles.

 

[Hurco550]

I finally got the oddball front bearings in the mail from China for the swap from the original 15mm TriZ axle size to the 17mm bw200 front axle size. I hope they hold up, because it's the only place I could find the particular o.d. and i.d. I needed.

Luckily the spacer had enough meat on it to bore out and use with the new axle. The old south bend 9 saves the day again.

 

[Hurco550]

Since I'm using the stock caliper mount on the rmz450 forks, I had to go up to a 250mm rotor. I chose an aftermarket KX125 KX250 KLX450R KX250F KX450F rotor for this job, as is uses a 4 bolt pattern as does the tri z hub. I drew up an adapter and had it water jet out of 1/2" 6061.

I counter bored the back side to accept the tri z bub.

Flipped it around and machined the front step for the rotor and a relief for the mounting bolt.

All mounted up, and it spaces the rotor out 1/4" away from the rim, which should help a bit with the clearance issues

Here it is against the original tri z rotor

 

[Hurco550]

I got a bit of tinkering done during the holiday break. Made a couple Top Hat spacers so that the RMZ Fork would accept the bw200 front axle. The unthreaded end will be split so that it will clamp the axle. The threaded end will not be split, but held in place with the pinch bolts on the fork.

While I was down in Georgia for Christmas I found a front-wheel from an ATC 250R for sale about 40 minutes away for $40. It is an 11 by 6.5 wheel which I will run on the rear. It is funny how close the gold anodized finish is between the Honda and Yamaha wheel.

I ordered a front and rear tire off of Amazon. The rear is a 24 X 10 R11 and the front that I ordered is a 27x 9 R12. The rear mounted up just fine but it became pretty obvious that the front was going to be far too big and bulky for the project. I made a trip up to Iron Pony and picked up a 25 x 8 R 12 swamp Lite for the front, which seems to be a favorite pick by the bw200 guys. It took some finagling with ratchet straps and some starting fluid to get it Seated on the rim.

Rear.
.

Front.

I made up a quick tear hub, swing arm and triple trees from wood just to do a bit of mockup.

The forks are a little bit on the long side so I will probably have to use a combination of internal lowering and sliding them up a bit in the triples to get everything where I need it to sit, but overall it is fairly close. The swingarm looks a little bit long in the mock-up but it is only an inch longer than the stock xr400 swing arm , and I have to leave myself enough room to build a jackshaft in front of the wheel yet keep it far enough back that my foot won't be into it.

 

[ridesolo]

Really lovin' that, Levi!

 

[Maritime]

Looks rad. I like it.