XR650R 1x Baja 1000 Replica Build

The XR650R had a very successful stint as a Baja 1000 race bike from the early naughties with Team Honda USA with riders like Johnny Campbell/Steve Hengeveld/Mike Childress. I will not attempt to go into the history and stats (as these are easy to find with a Google search), but in short the XR650R kicked ass from its first year to its last, when it was replaced by the more nimble CRF450. It has however still got a strong presence amongst the more amateur desert racers even today.

I have chosen to replicate the Team Honda 1x bike from the 2005 Baja 1000 as it was towards the final development of the race bike prepared by Precision Concepts and has the best mods I feel. This page will document what I have done so far and what is still left to do (mostly in pictures). I want it as close to the original within reason (reason meaning: there are parts that are incredibly rare and not entirely known to many people and the full extent of the engine mods was a very secret operation and remains so until today).

If nothing else I hope this helps anyone else who would like to find any of the parts needed in the future for their own build. As of 2013 parts are getting hard to find and If anyone needs help please ask!



Early days (March 2013)


Parts begin arriving








Early progress


As it looks today (12/07/2013)






Parts are coming thick and fast right now, but the only bits I can't get my hands on are the JC signature BRP triple clamps and the works rear calliper (not likely to get this though). I have been blessed with help by those involved in the Baja XR's and people connected to the riders and I would like to thank everyone for helping so far.

More specific information about the work done and the parts needed will follow over the next few days/months. I hope to complete the build by latest December 2013.

Long live the 'Baja King'!

My 2000 XR650R (Aussie spec, road legal with uprated stator and all the electrics) was not the most ideal base for this build. There were many signs of its age showing, and as new shiny parts started to arrive I knew I had to make the old things look new again!

The first thing to tackle was the frame. I took it to a local bike paint shop and came out feeling let down. The guy I spoke to was friendly but he didn't look positively on getting my frame sanded and painted/powder-coated. His exact words were: "it'll take a lot of hours", "won't be cheap" and "I have never done a dirt bike frame before, the oil tank is a problem".

With pressure building on getting the build done right, I thought I would find a better solution and do it myself. I looked at what is actually on show once the bike is fully built, and also what on my frame was looking tired. Years of leaking coolant had pitted the lower cradle and the side uprights were scuffed (the tubular parts of the frame, I polished the cast bits but left them as they were)


I decided to sand these areas by hand, using first a 240 paper and then a 400 to finish. It took several hours and also an electric drill with wire brush bit to get at all the corners and provide an even finish. I had to sand lightly to finish, and only in one direction to create a nice 'brushed' aluminium look. End result is it looks great! It will be open to the elements and I don't expect it to stay this nice, but I can always maintain it by lightly sanding it again.




Using a top quality aluminium polish also adds a layer to protect the exposed aluminium from the elements.

**For any purists reading this: I discovered that the 1x bike also had 'brushed' aluminium on the uprights, so this method is in line with the real thing **

I may have polished my frame a little

Nice! How has yours held up since polishing cognugget?

eh... not bad... I have been on mostly street with over the boot pants. When I did my dune trip it got really messed up. Still looked better than it did before i sanded it down.

Cool thread, I almost forgot you were doing this.

My only question so far is for the shock; what is the deal with the red anodized rebound adjuster?

I am super curious what the motor mods are also.

That is going to one clean looking bike.

Im in!

Me too!

Hey Crypto, I really should have started this thread ages ago but rather late than never!!

The rear shock used on the original bike was a Precision Concepts hybrid of a CR500 upper and XR650R lower. Two way postage to PC in the states would have made it a very expensive choice for the build so I picked a local suspension shop that has experience building these hybrid combinations for the big XR and gave them a specific brief to not only get it as close to being the real thing, but also looking like the real thing :eek1



So the red anodized bit you mention is the 'high-speed' adjuster on the CR500 part of the shock.


The benefits of the hybrid shock are:

larger shock body with more oil, better for cooling and less fade when hot
High speed adjuster for desert racing
Slightly longer stroke, meaning a raised rear end to the bike

The original had a titanium red spring, which I could not find so David at Suspension Matters found the correct non-titanium spring for my weight and got it powder-coated that Ferrari red to match the race bike. The internals of the original are largely unknown as Bob Bell and his team kept the internal mods on the low down. I am sure Adv inmate BUMP will know more as he has had a lot of contact with the Precision Concept guys over the years the XRR was raced. I however had to choose the best parts available to me, so I went with a revalve and a race tech Gold Valve along with a total overhaul of the seals on the CR500 body.



Engine mods to follow soon

The 1x XR650R had many different configurations tried by Bob Bell and Honda and it is almost impossible to know exactly what the 2005 Baja 1000 winning bike had going on inside the motor.

From my research I have ascertained that some amount of porting and polishing was done on the internals of the head, they fitted the HRC kit pictured below, minus the high compression piston (apparently to reduce power slightly as they were struggling with traction). There were air intake mods like the HRC airbox cover mod and something called a 'Bat Wing' which was an aluminium scoop inside the air box to smooth air flow into the carb. They also had the CDI tweaked to increase the rev limiter and produce better characteristics for desert racing.

Bad news is the motor is one area that I didn't modify internally from my already modified but sad looking XRR motor:


There are a few reasons for this. Firstly I can't find an HRC kit, they were discontinued years ago, secondly my motor already has a Stage 1 Hotcams and Vortex programmable CDI fitted and I feel that it already has the punch to make this bike a scream to ride and it was done not long ago.

I will however be adding a Pro Circuit reverse megaphone race exhaust system and the Bat Wing mod to make it closer to the original 1x bike. If I come across an HRC kit one day, I will jump on it and do the motor justice by fitting it, but for now I am being realistic and moving on.


Now, the other aspect of the motor is how it looks. As you can see my poor old XR had a tired looking motor and it needed some freshening up. I started by removing it


I blanked everything off and used a solution of aluminium cleaner and water to scrub the casings all over. After many hours it came up looking as fresh as a new one! As with the rest of the bike I also removed visible bolts one at a time and polished them with my Dremel . I also got new clutch and stator covers which makes a big difference visually!

And here is the finished product:


And here is a Precision Concepts motor (not the 1x but similar):


For more on the Bat Wing mod please see my future posts

Hang on a second.......Did you also polish the kick starter?!

GREAT idea, good luck with the project!

Maybe

Thanks Garthe, much appreciated!

There are many myths and opinions on the Bat Wing that was developed by Precision Concepts and Bob Bell, and I have found many approaches to re-creating the design. My first step was to contact PC and find out if they had any of the Bat Wings lying about and this was their reply:

"Jonah Street came up with that. I wish that we would have saved one as a template, but we didn't. Diane"

So, I began my search for the best approach. Put simply the Bat Wing was a piece of aluminium fixed inside the air box to smooth out the airflow into the throat of the carb. Bob and his team quickly noticed from the first prototype race bike that the XR650R air box is one of the worst designs for a race air intake. The aim of an air box is to filter and provide enough air to feed the fuel ratio at any RPM, and in a racing bikes case that needs to be at its optimum at high RPM, when the bike needs the most air at once.

Something had to be done and Jonah Street along with some aerospace input came up with one or both of the following designs (since posting this I was made aware by Mung that the second design is an original so I will find out more before confirming one or the other) to smooth the airflow:




This first design looks easier than it may seem to make. You have to bend and twist the aluminium in several directions and it is important that you seal it around the edges to prevent air getting past. The throat bend is quite short too. This design is unlike any other attempts I have seen. The second is simpler to make as it just bolts top and bottom and sits in the middle of the air box.

Here is an attempt made by another owner:


I had already begun to make my own Bat Wing when I found the original photos of the Baja bike's Bat Wing so I contacted fellow inmate Burpsa about his attempt and he kindly gave me a pdf template of his design plus some info on where he felt it could improve. One area being the throat which I then looked at making longer so that it goes right up towards the carb.

Here is my attempt in pictures:
First I made a template out of 0.6mm aluminium as it is easier to cut and shape

Note the much longer throat, the challenge was going to be how to keep it from flapping


I then made a few tweaks here and there to get it fitting right and then cut the 1mm aluminium into shape, and this is what it looks like




I also polished the aluminium surface to make it super smooth. The theory with this design is that it channels most of the air to the left of the Bat Wing and doesn't reduce the volume of the air box for lower RPM use. Coupled with the HRC spec air box cutout it should be effective at getting most of the air to the intake as smoothly and directly as possible.

As the bike is still being built I have not been able to test it, but with my aerospace experience in the air force and a bit of practical theory, I can see it doing a pretty good job. One of the myths has been a 'massive power gain' but this is optimistic in my opinion. For most normal trail riders this Bat Wing may not be too noticeable. I suspect that with the correct exhaust system (T4 Megaphone type) it aids overall air flow and therefore helps the engine cycle by making air more easily available at a certain RPM.

The throat feels solid so hopefully it won't flap once air starts passing over it. I will be making the 'original' design too and then try both side-by-side and decide on the best for my bike.

Any questions/ideas please fire away

Bike's looking sweet - I've been thinking about making a bat wing for awhile, just haven't gotten around to it - Looking forward to the results of the with and without test

Thanks ded, yeah it will be interesting to find out - I may need to Dyno it for a true reflection and just have two air boxes, one with each ready to swap between runs. I will look into that once the bikes just about ready.

I'm sure someones got one to replicate one. I'd be interested in checking one out, just dont have the sheet metal skills to knock one out.

Don't use springwood Suzuki to dyno ya bike .......im not real happy with ol mate ..who broke my rubber seal when he moved the c-clip...then thought silicone would be ok :eek1

ill never use them again

Thanks for the heads up Sean-0, that's shocking!