49mm Showa conventionals conversion

FWYT
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2/24/2021 8:14am Edited Date/Time 6/7/2021 7:44am
I've been wanting to do this for a while and the plan was to get bike to do a full rebuild with and include the Showas in the mix. That is looking like it won't be in the budget for quite a while so I've decided to do the swap
on to my trusty 2004 KTM-200.

I had picked up a set of the Showas a while back in remarkably good condition. Actually, I have two sets because the first set was just OK. Even picked up an aftermarket top clamp of some sort. Both sets are from a 1998 RM250. I am going with the Suzuki clamps for the gullwing design that is needed for these forks.

First order of biz is to check the fit into the head tube. Remarkably, they both use the same steering head bearings. Holy crap!! One less hurdle!! Or do many bikes use the same size steering head bearing? I don't know, but I am relieved.

The stem in the Suzuki clamp, however, is just a little too short. I mean just a little, maybe 5-10mm. The collar that threads onto the stem at the top, under the top clamp, only can thread on about one turn.

I really don't want to get into a custom stem. Cross referencing a longer stem possibly? But looking at the Suzuki bottom clamp, the boss is raised at least 8mm. I think what I am going to do is press out the stem and take down that boss to essentially move the clamp up in the frame and give me the length I need. I am not an engineer but that does not seem like an area where removing that material will cause a structural issue. (Please tell me I'm right. hahhaa)






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2/24/2021 11:54am Edited Date/Time 2/24/2021 11:56am
I don't know if it's right, from an engineering stand point, but I have done similar things with fork conversions without issue. I've also bored the counter sink the stem rest in a little deeper to allow the stem to stick out a little more.

The other thing I've found this that some after market bearing kits sit a little higher than OE. Usually it has to do with the seal. Yamaha, for example, have a seal flange that allows the bearing to rest on the clamp. Many of the aftermarket kits have seals with a full faced flange that the seal rests on and makes the bearing sit a few mm higher.

That one almost looks like it has a washer under the bearing.

Hope that helps.
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FWYT
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2/27/2021 8:28am
I don't know if it's right, from an engineering stand point, but I have done similar things with fork conversions without issue. I've also bored the...
I don't know if it's right, from an engineering stand point, but I have done similar things with fork conversions without issue. I've also bored the counter sink the stem rest in a little deeper to allow the stem to stick out a little more.

The other thing I've found this that some after market bearing kits sit a little higher than OE. Usually it has to do with the seal. Yamaha, for example, have a seal flange that allows the bearing to rest on the clamp. Many of the aftermarket kits have seals with a full faced flange that the seal rests on and makes the bearing sit a few mm higher.

That one almost looks like it has a washer under the bearing.

Hope that helps.
Thanks, appreciate the encouragement. I pressed the stem out and there is definitely enough material to take down on that boss. I will be able to get 6mm easy. I got a 3/8" end mill, chucked in my crappy little HF drill press and started going to town. I think if I'm careful, I can keep it flat and square. Of course, the HF press motor decided to finally expire with a puff of smelly smoke a few cuts in so the project is on hold for now. hahhhahaha


2/27/2021 9:37am
Honestly, I've never taken that much off one, but we will see how this comes out.
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FWYT
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3/3/2021 6:34pm
Came across a little Ryobi drill press for cheap so back to work. Won't win any kind of machining award but it is flat and square. Now have to figure out how to turn a little material off of the stem without a lathe. Hahaha


The Shop

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3/4/2021 7:25am
Next step is to turn down a portion of the steering stem. The stem diameter is 30.3 MM where it goes through the bottom clamp and then is 30 mm where the bottom bearing presses on. So I needed to takedown .3 mm on about 6 mm of the stem. Laugh all you want but this is how I ended up doing it. Spun the stem and then carefully and slowly, with constant measuring took a Dremel to the area that needed to come down. Came out perfect. Well, perfect in the Lo-Brow sense. 😁 Should work just fine.

7
3/4/2021 9:43am
Bravo my friend. It may not be pretty, but a mans gotta do what a mans gotta do. I think they call that ingenuity.
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FWYT
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3/4/2021 10:36am
Bravo my friend. It may not be pretty, but a mans gotta do what a mans gotta do. I think they call that ingenuity.
Thank you! Much appreciated.

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3/8/2021 10:05pm
Getting back around to it. Clamps bolt in perfect. So relieved I didn't need to mess around with different bearings or a stem!

Next is steering stops. I'm going to keep it simple and carve up some aluminum and just bolt them in place using the existing KTM steering stop lug. Should be plenty strong. (still have to shape and finish them.)


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Kidkawie
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ქუთაისი GE
3/9/2021 3:10pm
You're going to love those forks. Nice work!
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FWYT
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3/10/2021 7:39am
Shapey, cutty, grindy, sandy . . . . looks a little funny hanging off into space in front like that
but it should be plenty strong. Side note- I picked up a crummy little Harbor Freight bandsaw a while
back dirt cheap but the older gentleman who owned it before me had taken the time to set it up
and it cuts just dead nuts straight. Sometimes you get lucky.







1
3/10/2021 9:01am
Looks good.

Can't wait to hear what you think of the conversion.
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FWYT
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3/15/2021 11:23pm Edited Date/Time 3/15/2021 11:55pm
Next step was to build a bracket to maintain the stock front fender/brace, and therefore also the front number plate. Also, I want to maintain the steering damper. (I really like those little Showa dampers!) After a couple failed test brackets coming up from the bottom of the clamp, attached to the fender mount bolts, it occurred to me that the former steering stops provide no additional structural strength (I don't think. :D) and I could tap into those. Milled them down a little bit for more surface and after some work, did this little bracket. Maintains the stock fender and everything fits. Snug, but it fits.

Edit- After looking at these photos, I realized that the portion where the damper bolts on should be trimmed to more of a "V" shape. I'll do that before moving on.








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FWYT
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3/29/2021 12:05am
Easiest part of this whole deal is rebuilding the forks! hahaha
I'm not going to mess with the valving yet as I have to ride it first
to see what's up.

Also going to go with the springs that are in it for now, as well.
5mm wire, 42.75mm OD and 23 active coils.
According to this calculator http://www.racingsuspensionproducts.com/spring%20rate.htm
the springs come in at .50kg/mm which seems way high. Oh well. I'll just ride it first
and see how it feels.


4
sreidmx
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3/29/2021 1:47pm
I’m super interested as well, these are supposed to be regarded as some of the best oem forks..
1
PTshox
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3/29/2021 2:57pm
wow... 50 is super high I agree. Racetech has a good spring calculator for rates... I'll be it comes in around 39-41 kg
PTshox
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3/29/2021 3:04pm
This is what I saw on the RT site... for single track.. It said stock spring is a 42. Hmm...


Stiffness Preference: Standard Stiffness
Age: 45 years and Older
Height: Standard Rider Height
Gas Tank: Standard Gas Tank
Lowering: Not Lowered
Rider Weight: 180

FRONT FORK SPRINGS
Recommended Front Spring Rate: 0.40 kg/mm (Use closest available)
Stock Front Spring Rate: 0.42 kg/mm (stock)
1
FWYT
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3/29/2021 3:32pm
PTshox wrote:
This is what I saw on the RT site... for single track.. It said stock spring is a 42. Hmm... Stiffness Preference: Standard Stiffness Age: 45...
This is what I saw on the RT site... for single track.. It said stock spring is a 42. Hmm...


Stiffness Preference: Standard Stiffness
Age: 45 years and Older
Height: Standard Rider Height
Gas Tank: Standard Gas Tank
Lowering: Not Lowered
Rider Weight: 180

FRONT FORK SPRINGS
Recommended Front Spring Rate: 0.40 kg/mm (Use closest available)
Stock Front Spring Rate: 0.42 kg/mm (stock)
Yeah, I saw that info on Race Tech, but couldn't find a calculator to determine what I have right now. Do you have a link?
FWYT
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4/1/2021 7:28pm Edited Date/Time 4/1/2021 8:14pm
We're getting close! As much as I wanted to do all the work myself, I do not have access to a lathe so a local shop, Motorcycle Dynamics Racing in Escondido, turned some spacers and an axle for me. Very reasonable price and quick turnaround! Randy is good people!

Yes, we're going with a little Ti hardware. Grinning

4
FWYT
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4/5/2021 6:38am
Last part is this caliper adapter.
Now I just have to get a day to go ride! Tongue
1
4/5/2021 4:44pm Edited Date/Time 5/20/2021 6:09pm
Looks good. Can't wait to hear how this mod works.
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5/20/2021 5:16pm
Finally got a chance to go riding. (Pathetic, I know, but hey what are you going to do? Got to pay the bills.)

Initial first thought is that I definitely like them more than WP's that were on the bike. No harsh slap down and soaks up those braking bumps better. I will hopefully be able to get to ride some more next weekend. Keep in mind I am just a 50+ B rider. Not some Pro who hauls ass. But so far I dig them!
4
garasaki
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5/24/2021 1:21pm
How bout a pic?!?
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FWYT
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5/24/2021 10:00pm
garasaki wrote:
How bout a pic?!?
Dang, you're right, I haven't even taken any finished photos. Will do the next time I'm at the shop.
1
FWYT
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6/7/2021 7:44am Edited Date/Time 6/7/2021 7:44am
Forgot about the finished photo! Whoops!
Went racing last weekend. I dig 'em. More supple on the choppy stuff and squares.
The rider needs work for sure, though!

I still need to trim the steering stops a little more as lock-to-lock could be better.

Overall I am very happy with how this whole project worked out!!


5
FWYT
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7/24/2021 1:00pm
I'm still loving the results of this project! I completely get the saying "The best you've ridden is the best you know." and I can't sit here and tell you I am super fast or that I've tried all sorts of exotic set ups, but for a few hundred dollars and some time, I'm finding these as good or better than the forks on my other bikes in the past and haven't turned a clicker. Plus the DIY satisfaction. Good times!


4
7/25/2021 4:01pm
I think those forks look awesome on there. And you look like you're hauling in that picture. Very cool.
1

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