XR400R Inverted Fork Project

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XR400R Inverted Fork Project

Post by 4Strokes » Mon Jun 06, 2016 11:39 am

Topic: Project XR400 w/inverted fork (finally finished!)
Author: ThumperTDC
Posted: 10/20/2005 12:02:45 AM

I have recently started yet another project for my bike. Over the last 2 months I have collected all the parts I felt I needed to accomplish this project off of eBay.
  • 2000 CR125 forks
  • 2000 CR125 complete front brake system
  • 2000 CR125 complete front wheel
  • 2001 CR250 triple clamps both upper and lower
  • Race tech gold valves
  • 1996 XR400 stock triple clamps w/ steering steem
  • 2004 CRF450 White front fender
  • 2000 CR125 lower fork protectors
Last weekend I started in on some machine work. I started to mill the CR triple clamps. I felt I had to machine off the stock CR steering stops since it appeared like they would come into close contact with the stock oil cooler.
Lower clamp finished and somewhat cleaned up
Next came the upper clamp. I had noticed that the lower clamps from both bikes the XR and CR were just about the same thickness when I measured them. The upper clamps off of both bikes were no where close to being the same thickness. I was starting to think I was going to have to make a new steering stem that would be longer. Then i realized why can't I make them the same thickness and still be able to use the stock steering stem. So I started cutting on the upper clamp.

The upper clamp after it was machined to the same thickness as the XR400 upper clamp.
I will still have to make a small sleeve so the stock XR steering stem can be pressed into the lower clamp, as well as another one for the upper clamp.

10/24: Today with a little help from my father in law we got the sleeve for the steering stem mad and pressed into place.
The sleeve was kinda tricky to make, since it had to have a flange on the bottom end as well as being cut out in the inside to mate up with the flange on the steering stem.

10/27: Today I got the upper sleeve made and got the forks installed. The upper sleeve was a fair snug fit, but it was secured to the upper clamp using red loctite, it ain't moving. I packed the new lower bearing with grease and pressed it on. I cleaned the upper bearing up since it was barely a year old and repacked it with grease. Torqued the upper clamp nut and installed the fork legs.

One thing I did notice is that it definitely does not turn as sharp as the stock forks (which I knew was going to happen). I got to comparing it to how far my YZ will turn and it seems like it still doesn't turn as far as my YZ does. New steering stops will have to be made, still up in the air on exactly which way I am going to go on that. The bolts on the lower clamp end up touching the tank, so I won't be testing it until the stops are made.

The gold valves and new oil seals should be in by tomorrow so that will be the next task to complete. The forks will be topped off using Amsoil suspension fluid, used it last time ans really liked it.
After the revalve and seal change I plan on making something similar to these hand guard mounts I made for a buddy. But the new ones I am planning on making will have the tie-down holes along with a way to bolt my headlight to them, similar to the WRF's headlight bolts on.
11/2: Well I got the tie-down mounts finished and mounted. I drilled and tapped 2 small holes, one on each side to mount my front headlight to.
11/15: Went and had the new steering stops welded on. I had made them to fit one way on the clap, I showed it to the one guy at the shop I went to and he then passed it off to another guy to weld it. He ended up welding them on backwards. I didn't realize it until I got it home and got pissed. Well I slipped it onto the bike and it still stops where it is supposed to. I am thinking I will machining off just a hair off of the stops to gain just a little more turning. The welds didn't turn out to be the best looking in the world, but they are welded on and should hold just fine. I'm not sure how well a weld can turn out between cast and billet aluminum. Might work on smoothing it out a little to make it look purdy. I will get some pics posted soon.

11/19: Ordered new white Polisport '04 CRF450 front fender and lower fork protectors. Now its time to start the fork rebuild. Should have it up and running within a week or so.

11/26: Tore down the forks got the seals replaced in one of them, have the other tore down ready to remove the seals in the other. I got the race tech gold valve installed on one of the forks, but at this time before I install it I want to be absolutely positive that I have it done the right way before I reinstall it to the fork. The last thing I want to do is to tear it back down because something doesn't work right.
Stock compression valving
RaceTech compression valving with Gold Valve installed
Stock valving spread out
RaceTech valving spread out 1
RaceTech valving spread out 2
When I have it confirmed that I do in fact have it the right way, it will be going back together and filled with some AMSoil suspension fluid. I used this stuff when I rebuilt my XR forks and shock and really like the stuff, so $20 for 2 quarts is worth it to me.

11/28: While at work yesterday my fender and fork guards were delivered to my house. It is starting to come together. I cant wait to get my new CRF front fender mounted up and everything back together to take some pics to post the finished product.

12/3: Today I got the forks all put back together and I got the new fender and fork protectors mounted. The only thing left to do is to secure the lower part of my headlight and install the front brake caliper and master-cylinder. Then its ready to go test ride.
steering stops made and welded on
This is a little tool I ended up making to tear my forks apart. The forks require a 14mm Allen socket to tear them apart. Well I had spent most of the morning going all over the place to different auto parts stores and tool places with no luck. I ended up going to my local hardware store, buying a 1" long 3/8" bolt and 2 3/8" nuts. The outside diameter is exactly 14mm. I got the nuts lined up and I welded them in place and then filed it smooth. $0.27 later I have a little tool to remove the compression body from the lower fork to tear them apart.
little tool made to tear forks apart
1/2: Well today I just ordered some new small items to hopefully finish off my project. I ordered a Fastway dual clamp for the brake line and trail tech computer cable. Hopefully they both will fit. I ordered a new master cylinder cover which has raised fins for cooling, not that my front brake fluid would get hot, but its more for the trick factor, its anodized red. Then I got some front brake pads cause the old pads that came with he caliper were shot.

1/17: Got the items I ordered. Went to install my CR front brake setup and found out the CR brake line is about 5" shorter than the XR. I ended up reusing My XR front brake, caliper/line and master cylinder. Before I started this project I looked up all the parts needed to complete this. I noticed that the caliper mounting bracket had a different part number than the XR mounting bracket, so I went ahead and found a complete front brake setup on eBay cheaper than what the bracket was going to cost. After finding out the line was 5 inches too short I started comparing both brackets, and low and behold they looked dang near exactly the same. I bolted the XR bracket up and so far seems to line everything up perfect. The only thing left to do is mount up my trail tech computer and I will be completely finished with my project.

Reply by Admin on 10/20/2005 1:49:26 PM
You're doing some nice work there, thump!

Reply by ThumperTDC on 10/20/2005 11:01:01 PM
Thanks, when I'm in the shop working, it kinda takes my mind off of what has happened these last few weeks, its quite relaxing for me.

Reply by OldnTheWoods on 10/22/2005 09:42:30 AM
Not familiar with "what's happened these last few weeks", but very impressed with your work there! Anxious to watch your progress. I still don't understand how the Race Tech "Gold Valves" can possibly be superior to modern fork technology. John

Reply by ThumperTDC on 10/22/2005 10:55:47 AM
Originally posted by OldnTheWoods
Not familiar with "what's happened these last few weeks"
I think the last line in my signature will explain it. There are also a couple of other thread in the lounge section explaining.

Reply by cdndrtbke on 10/23/2005 2:37:16 PM
i just had my bike out this weeknd with the new USD forks and ts awesome. wicked control and feel. its not yet set up for my weight but will be next year

Reply by ThumperTDC on 10/24/2005 12:28:46 AM
Did you figure out your steering stops?

Reply by b_king on 10/24/2005 12:59:21 PM
They there Thump, you should ask Admin to put this up as one of the Honda mod's under the tech section. With you expert advice and guidance, I am sure anyone could accomplish this mod! Keep up the good work!

Reply by ThumperTDC on 10/24/2005 11:18:02 PM
When I am completely finished with it, I plan on doing a nice write up once I am finished. This thread is more of a Diary of my work so to speak. Currently uploading some new pics of what I got accomplished today.

Reply by cdndrtbke on 10/25/2005 3:08:50 PM
for the steering stops, i made two stops out of one of the stock handle bar clamps. all i did was cut it in half and grinded it until i had the shape and size i wanted. i had my machinist weld it on because i don't have the stuff to weld aluminum. it works great and holds up well because i bailed hard this past weekend and no damage done to them.

Reply by Rotorcraft on 10/25/2005 7:17:34 PM
sweet machine work, I'd love to have some tools like that to work with. Aluminum is a very nice medium to work with.

Reply by RideRed on 11/03/2005 7:53:26 PM
Nice work Thump! After looking at the mill setup, I'm jones'n for the years I spent cranking dials on Bridgeport's and lathes in my former life. I'd love to get one of each and put them in the new garage I'm planning to build.

Reply by ThumperTDC on 11/03/2005 10:44:05 PM
I'm havin fun playing around with them. Hopefully one day they will be mine.

Reply by lseann on 11/05/2005 06:43:49 AM
I would think that someone with access to milling machines/lathes could do quite well for themselves just fabbing up/selling the triple clamp bushings required for these fork swaps. It took me forever to find a local shop that would do this work without a blueprint and exact measurement requirements. Most of them told me that they would not "reverse engineer" my parts. Anyway, I'm really impressed by the work you've done and the pics are great! I had an idea that maybe the stock CR steering stem could be cut and used to make the bushings required by boring/drilling the inner portion to match the outer of the XR stem. Just an Idea. On a side note, anyone looking to buy just an XR400 steering stem and can't locate anything used, Emig racing sells them for about $70.00.

Reply by mcdavis on 11/19/2005 11:21:21 PM
cnddrtbike, checked your pics. nice ride. the bike looks sick. so does your thump! i really want to do this mod but isn't there and easier way, that is, take a pair of inverted forks that are 43 mm in diameter? this was the size used on 92-95 cr's. has anyone done the swap this way? thanks

Reply by cdndrtbke on 11/20/2005 10:25:50 AM
There's no way a pair of inverted forks will fit into the stock XR clamps. the clamp holes are way too small. if it were that easy i would have done it myself. the way i did it wasn't hard to do, mind you i didn't do the machine work myself because i don't have those kinds of tools, but i did hang out in the shop where it was done and watched the guy do it for me. didn't look to hard at all. after the steering stem is all done, it pretty much bolt on from there. all you have to do is fashion some steering stops out of something and have them welded on. don't forget to buy a caliper mount for the year of the forks you buy unless you plan on using the entire front end of a different bike.

Reply by bpoulter on 11/20/2005 2:41:05 PM
Hey ThumperTDC this running commentry is great and timely as I've just sourced some Ohlins and CRF 250 triple clamps off eBay for my Motard XR!

Looking forward to racing next year with some stiff forks that don't fold under braking and cause excessive tire chirp on the tar! Saw some great supermotard racing here in Sydney at the Olympic Park. Micky Dymond and Michelle DiSilva from USA were great, full on great turn of speed. Michelle was riding a 250 and the woman's class was run with the vets. The only reason she didn't beat them all on the track is the fastest vets KTM 525 left her out of the corners and down the straights, but she'd gather him up under brakes and stuff a wheel up the inside with the back hanging right out! However local 18 Troy Herfos won the main race, hes been wining on recent trips to the USA and Europe, so he knows how to mix it up with the world class guns.

Reply by SpeedyManiac on 11/23/2005 8:54:31 PM
Originally posted by cdndrtbke
theres no way a pair of inverted forks will fit into the stock XR clamps. the clamp holes are way too small.
What is the diameter of the upper fork tubes on a stock XR400R? The forks on my Gasser are 43mm inverted.

Reply by ThumperTDC on 11/23/2005 11:11:56 PM
I can't remember off the top of my head how big they are. My new CR125 forks are 46mm. The thing to remember it that the clamping point between inverted and conventional forks are different. I believe the area on your forks that is measured is the lower fork legs, where as on the XR it is the upper forks where it gets clamped. cdndrtbke is correct though they are way too small for any inverted fork to fit. I didn't realize how small it was until I saw it sitting on the shelf.

Reply by bpoulter on 12/02/2005 03:28:13 AM
wo hoooooo... its starting to come together just put the CRF450 triple clamps on the Ohlins forks last night. Ordered the stem from Emig this morning and the CRF450 Axle and spacers to match the CRF450 wheel winging its way from USA to Sydney.

Man I love eBay its just so easy to do this stuff now. Back in the 70's it was research at the local library and bike shop then phone and troll the wreckers. Took so long and nothing you wanted was available or it had just sold.

Interesting fact my shortened/lowered SM Ohlins are the same length as my XR400 forks, but I can lower them more in the CRF clamps.

Roll on 2006 I feel there's some serious tarmac scraping coming on. The table top jumps should be a bit smoother and front patter under tire squealing stopping should be a thing of the past.

Reply by ThumperTDC on 12/03/2005 4:08:12 PM
Almost finished, I updated my progress report with pics.

Reply by bpoulter on 12/20/2005 02:50:41 AM
Hey ThumperTDC, I'm looking at the fit of my Emig steering stem and the CRF450 top triple clamp and there is not much clearance to put a spacer in. However it is too loose a fit to just bolt up. Did you bore out the hole in your top triple clamp and then make a spacer? That's what I'm contemplating doing. Your bike is looking good. Can't wait to get mine sorted in the new year, my gold Ohlins are going to look goo with the black front end and wheel!

Reply by ThumperTDC on 12/20/2005 08:39:31 AM
My clap should be the same as the CRF's, we managed to make a spacer without messing with the hole. It was really thin, but it was enough to fit in there.

Reply by Admin on 12/20/2005 09:14:25 AM
Originally posted by ThumperTDC
My clap should be the same as the CRF's, we managed to make a spacer without messing with the hole. It was really thin, but it was enough to fit in there.
Thump, I think you should go see a doctor about that! :o

Reply by ThumperTDC on 12/20/2005 12:38:17 PM
Ha Ha, it was a long shift yesterday, had 2 calls after midnight, then having to write the reports makes for not much sleep.

Reply by cdndrtbke on 12/20/2005 1:31:06 PM
Originally posted by Admin
Originally posted by ThumperTDC
My clap should be the same as the CRF's, we managed to make a spacer without messing with the hole. It was really thin, but it was enough to fit in there.
Thump, I think you should go see a doctor about that!
HA HA HA, that's hilarious Admin. that gave me a good laugh! :lol:

Reply by bpoulter on 12/21/2005 2:46:12 PM
Hi guys, thanks for the reply Thump and the comments about the doc had me cracked up at work this morning when I read this in an idle moment!

Yep from what I gather have not checked out parts books the CR250 2 and 4 stroke and the CRF450 have the same clamps. Not Claps!

Just put my CRF450 axle and wheel into Ohlins Fork clamp setup and discovered the axle is too short and the CRF spacers don't hold the wheel central. Another little machining job.

Know what you mean about lack of sleep we just moved house and are renovating the new one and moved out slowly from the old one over about a month. So its been work all day then painting after dinner till 11pm or so then doing admin dishes etc and bed around 1am.

Last night I just finished painting on the new renovation and stepped on the wrong part of the thin sheet of hardie cement product used as temp floor smashed through it. Injuries received include strained wrist, cut wrist twisted ankle and multiple bruising and 1/2" from squashing crown jewels! on the floor joist I ended up straddling. Paint from the tin flew everywhere! Fortunately no paint needed up on anything other than me and the framing and no cracked ribs or broken bones. Should all be fine to go riding in Jan when Sanosuke is here. I injured myself less last time I fell off the XR trying to go up a tricky hill at Louee. took me 4 shots/falls to get up it.

Reply by ThumperTDC on 02/09/2006 6:22:56 PM
One word, WOW. Made it out for the first time on the new forks today for a short ride with the wife. I will have a more detailed ride report a little later this evening with a couple of pics.

Reply by Admin on 02/09/2006 9:39:13 PM
Thump, your next project should be the header pipe. You may want to think about getting it ceramic coated, plated or find some good high-temp paint.

Reply by ThumperTDC on 02/09/2006 9:46:56 PM
Header wrap

Reply by Admin on 02/09/2006 9:56:09 PM
I think header wrap might create more rust.

Reply by ThumperTDC on 02/09/2006 10:01:36 PM
That's the beauty of stainless steel, no rust Hopefully Honda used a high grade stainless. If not I have a brand new stock header I can install.

Reply by ThumperTDC on 02/16/2006 10:52:49 AM
Went for a second ride on the bike Sunday, this time I was able to get a few more miles on the bike. Once again I had a grin all day out riding. The bike handles awesome with these forks. I am able to pick a line and stick with it, the bike wants to stay upright in the ruts. Even riding down trails with ruts and trying to stay out of the ruts the bikes wants to stay right where I am pointing it. I went on one trail and I can honestly say if I had my stock fork setup, I would have crashed. It was an uphill section of trail, not super steep, but steep enough there were huge water bars for water run off. I opened it up to see how it would perform. There were some rocks about the size of a softball if not a little bigger, so the trail was a little loose. I hit some of those rocks which wanted to wash out my front tire. They had me leaning over pretty good, but I was able to turn the bars and keep going. I was truly amazed, it the same thing would have happened with my stock forks with a fork brace I know I would have been picking myself up off of the ground.

I was told by a few folks that my bike would be more top heavy when out riding it. To be honest, the only time I can tell its a little heavier was when I am loading it on to my trailer without a ramp. These forks on my bike feel like they came from the factory on the bike.

Before I had messed with he stock shims in my XR forks. This had helped, the small hits you couldn't feel, but some of the larger ones you definitely could. The new forks and valving you really can't feel any of it. Riding down a gravel road you can tell they are stiffer, but as soon as you hit the trail and they start working you can't feel a thing.

At first, to me this mod was right up there with getting a pumper carb. I was not going to do it. I thought I had my stock forks dialed in, just like I had with my stock carb. I went into this project thinking that if I didn't like it I could resell it all and get my money out of it, especially since it would have been a complete front end. I was really nervous, I really like having a plush suspension to soak up the bumps, which was how I had my stock suspension set up. I honestly had my doubts with these forks, especially after I got the bike together and before I had a chance to ride it. With it complete and not that I have some time on the bike, I could not be happier with this mod. I am still up in the air if I would do this mod before engine work, but for those thinking about going this route, I say do it, IMHO its money well spent.

Reply by bpoulter on 02/18/2006 04:14:19 AM
Good to hear your report on the finished job. Sounds like the best handling mod after replacing the IRC tires with real dirt ones! Makes me keener to get my one going, it's on the back burner as the house is being renovated and lots of stuff is packed up and the XR is neglected out the back. No shed. I decided to go the USD route to avoid going to a fork brace and the modding the standard forks, only to probably go USD after that. Glad I made the choice. My main motivator was to stop tire chirp at 150km braking to 40km and leave the bike balanced after the braking to pitch it into the hairpin.

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