there several choices available when considering a fork swap, all revolve around mounting the usd forks.
| option | benefits | issues | parts required |
|---|---|---|---|
| Emig cnc stem and bush | very high quality majority of the work done for you |
cost require access to press to fit stem and bush must cut off lockstops |
forks top and bottom yokes emig parts new head bearings XR head bearing seals XR stem nuts and washer custom front wheel spindle custom wheel spacers or CR/CRF front wheel CR/CRF spindle CR/CRF spacers CR/CRF disc |
| Remachined stem and bush | much cheaper | need access to a lathe or machinst require access to press to fit stem and bush make a mistake and its scrap must cut off lockstops |
forks top and bottom yokes new head bearings XR head bearing seals XR stem nuts and washer custom front wheel spindle custom wheel spacers or CR/CRF front wheel CR/CRF spindle CR/CRF spacers CR/CRF disc |
| new bearings and spacers | very cheap very quick |
need to make or buy some 46mmx31mmx5mm spacers need to modify XR head bearing seals to accomodate larger stem diameter must cut off lockstops |
forks top and bottom yokes new head bearings XR head bearing seals CR/CRF stem nuts and washer custom front wheel spindle custom wheel spacers or CR/CRF front wheel CR/CRF spindle CR/CRF spacers CR/CRF disc |
| general issues | |||
|
- YES - NO - NO get a complete front end - technology has moved on - CRF forks are proper cartridge forks and much better quality than the CR ones - YES, if required - how many times do you want to take them apart? - YES if you do a custom spindle, NO if you dont. save some weight and junk the stock speedo for a digital one - pays your money takes your chance, if the bar mounts are cast into the top yoke then the forks are prehistoric, go for forks from a 1999 onwards CR or any CRF450 |
|||
tips for cutting the lock stops off
- fit some soft jaws to your vice or use several layers of duct tape to protect the yoke
- cut as low as possible with your hack saw to reduce the amount of filing
- protect the yoke with duct tape whilst filing
- clean your file regularily as the aluminium will clog the teeth, make it harder work and it will mark the yoke
- use the piece of lock stop you cut off as a file card to clean your file, gently brush it across the teeth to clean your file
- TAKE YOUR TIME!!
- DO NOT USE A FILE WITHOUT A HANDLE - you'll only do this once then learn the hard way how much pain a file tang can inflict ;-(
- if you havent done much filing before use tramlining to help you see what you're actually filing, to do this file in one direction then file in its opposite and you'll see lines left behind showing you what you're actually cutting
issues
- steering lock had to be cut off to clear handle bar mounts
- CRF wheel spindle 20mm compared to XR 17mm - spindle mods underway and will be detailed once complete
- speedo and indicator brackets will need to be remade
- Standard XR front mudguard fits with no problems
- Need to make lock stops
the usd build has been fairly straight forward. Once I got the conversion stem and bush fitted all that required doing was bolting the parts together. I changed the headstock bearings at the same time. The front wheel spindle has been custom made to allow me to run my standard XR wheels for off-road and my CR supermoto wheels on-road, besides the spindle I needed one new spacer made. The tricky issue has been the lock stops, I've seen people drill the yokes and fit bolts but at far as I can see theres no way they would line up properly, so I working on a bolt-on lock stop plate that fits on top of the front mudguard. The prototype has shown that it will work just need some thicker plate to make the final version out of. I'll post images and dimensioned drawings once its finished.
As the CRF yoke had bolt in handle bar clamps I also took the opportunity to fit a fat bar conversion kit from Apico and used some spare KTM fat bars.
a brief test ride showed some play in the forks, so I stripped them and replaced the slider bushes, very straight forward to do and as the bushes are cheap crazy not to. the photo shows the difference between a new and old bush.
issues 2
- usd forks are longer, so I dropped them 15mm through the yokes
- may need to change to lighter rate springs
- mk1 lock stop plate need to be made from aluminium plate, used 3mm will try 5mm - images and design to follow
- need a fat bar fitting kit for my hand guards
- photos show I really need to tidy my garage ;-)
usd strip - steps
- undo fork top - 50mm spanner - as these are cartridge forks the top will not spring off like on conventionals.
- pour fork oil out
- invert fork and undo botton bolt
- you now need to either make a tool as mentioned in the manual or do what I did and hold the fork end in a vice and place some wooden blocks underneath, this allows you to hold the locknut and remove the bottom bolt
- remove damper and spring assembly
- remove fork seal dust cover and stopper ring
- you now use the fork slider as a slide hammer to knock out the fork seal
- replace worn bushes
- reassemble fork and fill with new fork oil
-
usd update
-
didnt like the feel of the rubber mounted bars
had some aluminium replacements made, much better feel through the bars
conversion No.2 CR125 forks and remachined stem
After deciding to keep the XR I decided I wanted another USD front end, I could'nt find any CRF450 forks this time so managed to get some CR125 forks again at a bargain price via the bay.
This conversion was planned to be a serious budget one as I planned to keep costs to a minimum. After some shopping around I came up with the following -
- 2001 CR125 forks and yokes
- 2004 CRF450 front wheel, disc and spacers
- 2001 CR250 front spindle
the one good thing you soon discover is that most of the cr and crf parts from around 2000 onwards are interchangable, so you can mix and match whatever you can source.
Stage 1 as before is to remove the lock stops exactly as described above. This time however I did'nt use an Emig stem, I still think that if you can afford it this is the best option as their stem is beautifully machined, but this was a budget keep it simple conversion. The stems were pressed out of the XR and CR yokes for comparison. Basically the CR stem is longer by about 5mm and thicker by about 2mm. We decied this time to remachine the CR stem to XR size which is quick and fairly simple, the shaft needs the top and bottom sections reduced to XR bearing ID and the threads at the top of the shaft recut to XR size and made longer to allow for the thicker CR top yoke.
New forks seals were fitted along with fresh fork oil.
conversion no.3 bearing swap
ok this is the quickest and easiest conversion. make or buy some spacers for the bearings as they are thinner in profile than the XR ones.
these were new to me forks, so a strip revealed the normal shot bushes, so these were replaced along with the fork seals and fresh 5wt oil added.
| bike | bearing | specifications |
| xr400 | NTN 4T-CR-0574 | 25mm x 47mm x 15mm |
| conversion bearing | KML 30YM1/48Y1 - modified for TWF OD reduced from 48mm to 47mm TWF here |
30mm x 47mm x 12mm |
fatbars, conversion clamps and ezbleed valves added
