I suppose like with anything there are a number of obvious mods. We might as well list them. In the right hands the wrong tool can still be useful ; ) Summers proved this several times, the XR6 was by no means the best suited bike for the GNCC, but it is reliable, and with SRC's expertise it became absolutely bullet proof, went and handled significantly better than a stockie. These facts combined with the pilot proved a winning combination.
This page is purely the brainchild of a discussion on DRN forums, and is by no means a guide, use the info at your own risk.
Also having seen the Ballards prepped Glen Bell XR630 in action, 'twas a sweet sounding thing, pulled a big roost and looked good to boot. I saw it in the "flesh" at our local round of the thumper nats and at the time it made me drool. Ballards were reasonably successful in their open terrain motocross campaigns with the XR6, but their machines were heavily modified.
This is more than likely going to end up a wish list leaving an enormously overpriced bike ; )
| Suspension. |
Front: |
USD's of a late model CR250. Sprung and valved
to suit the application by someone with suitable expertise (Jeremy Wilkey
for example) Alternative: A well sorted pair of XR600 forks ('91 or later cartridge style) These would need to be sorted by an experienced suspension tuner. They only have compression dampening adjustment though, and the fork underhang is a notable problem. I believe these forks (or something very similar) were first used on the late 80's CR500's, so presumably they can be made to work. On my XR6 I've got preload adjustable caps, gold valves, WP springs, have removed the speedo drive with the use of a speedo drive eliminator, and installed an SRC fork brace. This is a HUGE improvement on the stock setup. I have been told in no uncertain terms (by several people) however that custom valving will outperform the gold vavles. |
| Rear: | Revalve shock, and use the appropriate spring. I
think Ohlins and WP have and aftermarket unit/s available that will fit (anybody
tried one?) |
|
| Frame: |
The frame would require strengthening in various
places are the XR6's are reknowned for flexing. I have a frame from
an ex thumper nats bike in my shed, I'll see if it has been gusseted etc.
But as has been previously mentioned areas of particular concern are
the upper rear shock mount (I have also heard of these being a problem) and
the bottom shock and linkage mounts. |
|
| Triples: |
Not sure if this is the 100% appropriate place for this but it will do. Perhaps the use of aftermarket triple clamps would be a good idea. Along with providing a presumably stiffer setup, the aftermarket top clamps often modify the bar position. I know I personally find the bar position too far back on my XR6. | |
| Steering Dampener: |
I've only ridden one XR with a steering dampener
(an XR650R) and while I liked the bike I didn't get to back to back it with
another without a steering dampener at the time. I've heard however
that they are certainly a good thing on in MX. |
|
| Brakes: |
Front: |
This is where some money can be well spent. An
oversize rotor kit would be good, quality braided line to improve feel (although
the XR6 lines aren't too bad), quality pads is CRUCIAL!!! Buy good pads,
they won't last as long but they will perform far better. I've heard
of people grooving them also to aid in getting the mud out. (as mentioned
below a CR master cylinder is apparently also a good mod.) |
| Rear: |
I ditched the rear reservoir on my XR6, and used
a length of braided line which runs up to near the seat. It achieves
a similar capacity but helps to avoid rear brake fade, which is common on
XR6's with aftermarket exhausts as they heat up the fluid because it's too
close. Ever noticed that Scott Summers bikes didn't seem to have one?
Apparently that's where this trick came from. Once again pay
for quality pads. An interesting alternative would be to use a CRF450R setup (i.e. master cylinder and reservoir in one) on an XR6. Not sure if it can be done but I recently saw some posts suggesting it could be used on other bikes. Has anyone considered this? |
|
| Engine: |
Exhaust: |
Large OD headers, and seeing as how it would be for competition only perhaps a big gun, or some other loud competition only pipe to extract the most ponies. |
| Intake: |
FCR Pumper. Although many people seem to be
using the Edelbrock Quicksilver carbs these days. There is also a train
of thought that the pumper carbs are a little wasted on the XR6 due to the
relatively large amounts of reciprocating mass. Never tried one so I
don't really know, but certainly ditch the stock carb in favor of at least
a mikuni flatslide. As an added bonus the XR's seem to start alot better
after crashes with flatslides, and don't seem to suffer from after jump bogging
nearly as bad. A K&N filter is certainly a good option to make it breathe nice and easy, some people don't like them but I've never dusted a motor with one. If you go all out the airbox should probably be modified to help is breathe better also. Some people cut holes in it, or open up the top by cutting the lip off and making the hole bigger. Ballards sell vents with filters that you can insert in the airbox. |
|
| Engine Mods: |
Probably the easiest way out here is to obtain a
HRC 628cc kit. I bought one recently brand new from a dealer at an
absolute rock bottom price. Do the rounds of your dealers to see if
they have one in stock. I think the US kits also come with the different
primary drive and jet kit also. The Australian kit comes with a complete
new cylinder, forged piston, rings, gudgeon pin, and clips to suit, HRC grind
camshaft, all the gaskets required, and heavier clutch springs. JE,
and Arias, have also made good quality pistons for XR6's in the past. Carillo
make rods to suit XR6's. Hardfaced rockers are also a good option. Aftermarket
valvesprings may help also, but the cam in the HRC kit works with standard
springs etc. Some aftermarket cams (for example some White Bros. cams
(which I think are ground by Webcam)) require shorter guides (due to
additional clearance requirements), heavier springs, aftermarket retainers,
collets and the like. The big bore XR's tend to pump a bit of oil out the breather tube, so it would be nice to get hold of an oil separator like the one used on Glen Bells bike, alternatively you could use the unit that honda had on the XR650L as standard. Ditch the auto decomp (there's an article with some info on doing that here) You could also just grind the lug off the front right exhaust rocker to achieve a similar result, but I removed the whole mechanism hence removing reciprocating weight from the valvetrain (not that you would notice it I suppose) CYLINDER HEAD: Cooling: This is almost a topic on its own. One known fact, XR6's get hot. The two main ways of adding additional cooling is either the Big fin treatment (which is derived from early HRC heads), or alternatively adding an oil cooler. SRC have a great kit to do this here If dollars were no problem I'd do both. XRs only claim its better to try and solve the problem by cooling the head with fins and avoiding the oil getting hot, whereas many others basically say that isn't enough and go for the oil cooler instead which realistically uses the oil as a coolant along with its intended use. Porting: XR6's can definitely benefit from porting, it really needs to be done by an experienced person however. With particular reference to the exhaust side you can greatly exacerbate the reversion problems inherent in XR's if you go about it the wrong way. Eric Gorr has done some work on XR6 heads in the past. It is also important to note that the XR6 gearbox gets a little strained once the motor gets to the 50hp+ mark (which isn't nearly as easy to achieve as many would have you think) If you go pulling crazy horsepower out of one you will eventually break it. |
|
| Sprockets |
I don't really know what gearing you would use for
an MX track, I'd suggest that 14:48 would be the absolute tallest you would
go. Possible something like 14:53 or 13:48 ????? A few things
to consider, I've heard it said that sprockets with an odd number of
teeth tend to wear better(with particular reference to the front), sprockets
with fewer teeth on the front are subject to more load, sprockets larger than
about 49 or 50 teeth tend to destroy the standard chainguide buffers fairly
quickly (if you use a standard unit), also the fit of the front sprocket onto
the countershaft is very important, a sloppy fitting sprocket is asking for
both to wear (replacing a countershaft is a big job) Afam, and OEM honda sprockets
are reputedly a good fit. |
|
| Ergo's |
Plastics: |
This is largely superficial, but Nice plastics can
make a race bike. The A-loop kit would have to be the obvious choice
I suppose (this has a more slimline seat with harder foam too I believe).
Along with an MX style rear guard (like
the one on this page) or the stock unit with the light removed (like summers
ran). Also a number plate for the front, aftermarket DHH, or the american
style headlight plastic minus the headlight (also like summers ran) The
australian headlights plastic and headlights are a somewhat cumbersome unit.
(check out a bike with an A-Loop kit here approx
0.5Mb) |
| Bars: |
This is really a matter of personal choice, I like
Jimmy Button Renthals on my XR6 which are a very large bar. Many others
seem to like CR high bend bars. But often these days Pro-Tapers certainly
seem to be popular and look the part. If you use large bars on the XR6
the manual decompression cable becomes a problem. You either need to
reorientate the lever upwards like Ballards did, or re-route the cable between
the tank and the bars rather than between the triples and frame ( I've seen
pictures of Scott Summers bike where it appears this has been done.) |
|
| Controls: |
Get a quick adjust clutch perch, one of the trick
fold back units that save levers might be good. Also apparently the
CR style brake master cylinders are an improvement, I'm not sure if you can
get a folding lever for that. |
|
| Pegs: |
Get aftermarket pegs, the '88 to'90 pegs were absolutely
tiny, and the '91 and later pegs weren't much better. I use IMS pegs
on mine but there are quite a few different pegs available on the market. |
|
| Grips: |
Use quality grips, there are a number of compounds
available. I found the medium renthal grips to my liking. There
is no comparison between quality ones and cheapo's. This actually is
money well spent. |
|
| Bullet Proofing: |
Aftermarket gear: |
1. SRC / Ballards / whoever. Kiwi style
Case Saver 
2. CR style or aftermarket chain guide. Perhaps like the Utah Sports Cycle unit which bolts up to standard lugs 3. SRC Clutch cable retainer (these break off the cases and could easily cause a DNF) 
|
| Weight Reduction: |
What can I ditch? |
Head light glass (and whatever other superfluous
gear goes with it), tail light, blinkers (only some countries models have
these), rear guard subframe, sidestand, front sprocket guard (use a
case saver in its place), crappy rear plastic chain cover, tool bag on rear
guard, speedo, silly bull bar like frame on the front of the frame, |
| What can I buy
to lighten it? |
At the top end of the scale, a few years back I saw
a complete aftermarket frame, with different geometry, supposedly somewhat
more rigid, and lighter to boot. Not sure who made it but it was in
the states. Magnesium stator cover, and clutch cover cases could be used of an '88 to '90 model XR6. (They should be physically the same) Strip down the wiring harness (not much to be saved here though) Wheels: Aftermarket Hubs, rims, and spokes, this could help to reduce your unsprung weight as well as strengthening the show up. Talon, and excel come to mind. |
|
| Electrical: |
Mods: |
Remove the spark plug cap resistor and replace it
with some appropriately shaped copper rod. Strip down the wiring harness and keep only the bare minimum. Use a CR style kill switch. |
page still under construction.
any ideas? CONTACT JUSTXR.COM