2001 CR250 $pecial Restoration Part II - Recreation of a 1999-2000 Japan Honda Factory RC250M

Thanks so much for the video. I was doing some research and Keihin sells a "Quad-vent" PWK carb which they say "the Quad Vents eliminate post-jump bogging from fuel plugged vent passages". When the HRC team switched over to the Mikuni, they may have tried to emulate what Keihin was doing with the vents. HRC found that the Mikuni made a little more power on the dyno.

I suppose the removal of the choke was an additional mod they did to improve throttle response, but I have no details.

Thanks Chuck.. I went back and looked at my translation of the Japanese article where they explained the details of the 2000 RC250M and it stated;

"One of the major changes on the ’00 RC is the Mikuni TMX carburetor.  It uses the same 38mm diameter bore as the ’01 CR250R, but the choke system has been removed and made into a special “short carb”. This is believed to improve (throttle) response."

There are still a couple of HRC parts I would like to find to really finish this build.. 

1) HRC rear brake master cylinder (for 00-01 frame)

2) HRC rear brake pedal that fits the new style master cylinder (I have the older style HRC brake pedal to swap)

3) HRC front number plate (NOS or good condition)

If you have or know the location of any of these HRC parts, please PM me.  Thanks!

I have been looking for the prototype cast magnesium rear master cylinder for years without success. The HRC unit looks similar to the cast aluminum OEM unit from 2002, with the exception that the HRC unit had a longer lower mount to accommodate the 00-01 frame and give the reservoir a more upright position. This also required lengthening the arm on the backside of the brake pedal.

I tried mocking up the oem "new" style master cylinder together with the previous version of the HRC brake pedal. It looks like I can make it work if I weld a little more length to the lower mount and redrill and tap the lower bolt hole. In the picture I compare my mock up (on the left) side by side with the original HRC set up on Frederic Bolley's 2000 RC250M (on the right side). I think it looks quite close and will have to do until I find the HRC rear master cylinder.

Bolley's frame mount is the same as OEM, HRC only lengthened the bottom mounting arm of the master cylinder.

There are very few generic HRC bolts on the 1997-2001 RC250M's, aside from the engine cases. Most all of the HRC titanium bolts are made to be used only on one location on the bike. The triple clamp bolts, seat bolts, radiator shroud bolts, rear subframe bolts, side panel and rear fender bolts are all designed so that any locators washers, bushings, etc. are machined as one single pieces, whereas the oem parts may require 2 or 3 pieces of hardware. I assume HRC did this to make it easier to disassemble and reassemble body panels/ parts quickly w/o have to search for the hardware that goes along with the bolt. Here are some pics of titanium body panel fasterners with the locating shoulder machined into the bolt.

Here is an HRC triple clamp bolt. Honda HRC always had to do things differently in those days.

Not being able to find the prototype magnesium HRC rear brake master cylinder for the moment, I am in the process of modifying an OEM master cylinder from a 2005 CR250 to make it look similar. They already look fairly similar except the OEM unit is cast aluminum, the "Nissin" logo is in a different place on the casting, and the lower mounting arm is a different length. Clayton from Trick Engineering is going to lengthen the bottom mount for me, but I had to build him a model and jib so he could figure out what the final mount should look like and be positioned.  

I used modelling clay to indicate how the arm should be and hardened the clay in the oven. Additionally, I made a template and a cardboard referencing arm so the fabricator can understand how long the arm needs to be and how positioned. You can see that the position of the mounting hole need to move to the right and upwards slightly.

I also started reshaping the housing to make it look like the HRC prototype part. In my pics above (see 1999 RC250M with green plates), you will notice the first version of the HRC MC had no writing on it and was very squarish and blocky. These first appeared on the bikes at the end of the 1999 season. Most of the season, they used the older style MC with the remote reservoir. In 2000 (bike with red plates)

A second version of the prototype HRC MC appeared that has Nissin written on the integrated reservoir. It is not as blocky as the first version, but does not have as many rounded edges as the final OEM production part.

To make the oem part look like the HRC prototype part, I filed the bottom side of the housing, which is very flat on the HRC part and rounded on the oem part. Unfortunately, I filed to far, not thinking that it would be thinner where Honda machined a groove for the C-clip. You can see where I file through. Bummer!  I just bought another off ebay and will start again. I also used a dremel tool to remove a circular casting mark and the "3/8" symbol from the oem parts as they are not present on the HRC part. Finally, the protruding edge that protects the banjo bolt at the top of the housing was squared off and a hole was drilled for the safety wire to resemble the HRC part.  The machined/ filed portions will be then treated with muriatic acid to recreate the cast finish. It was coming out so nice until I screwed up and filed through the housing .

The oem MC has some kind of coating on it.  I may either strip and soak in boric acid to create an aged magnesium finish or Cerakote it with a "Satin mag" finish to look like fresh magnesium. To replicate the HRC MC cap, the grayish coating will be removed from the OEM part, and the bare aluminum polished and clear anodized the way the HRC caps were. It will look the part when done.

I have procrastinated a long time as I didn't want to tear the bike down just yet, but I am finally getting the bike ready for a number of HRC modifications to the 7020 aluminum frame that require some TIG welding. The mounts for the HRC skid plate will be added along with square tubing across the lower frame spars around the exhaust port area. 7020 aluminum is very hard to find, but I was able to source some 7005 aluminum square tubing. HRC also modified the rear swingarm to fit the prototype rear brake caliper. The guide for the caliper bracket is a different size than what was used for the older style caliper and welded in a slightly different position on the swingarm.. I am sourcing the newer guide from a donor 2005 CR250 swingarm. I will but the guide off the donor swing arm, cut the one off the 2000/2001 swingarm, and then TIG weld the one from the donor swingarm onto my swing arm. The billet CNC HRC caliper bracket is also different.

More mods and parts to come.

Thanks Mike.. I am still kicking myself in the butt for grinding through that nice MC casting.  Any new ideas for your build? Still looking for any parts?

Here is a good shot of the first mag casting of the prototype rear MC that Nissin made for HRC.. very blocky, no writing/ on it.. The MC cap is similar to oem but doesn't have the "ears on it that Honda must have added to make it easier to grab and lift off the cap. I will grind those off.

Here are some more special parts used on the 1997-2001 RC250Ms.  Look how much sexier this HRC clutch push rod is compared to the OEM one piece part. The HRC pushrod is 3 pieces... it is titanium in the middle with hardened steel on both ends.

The engine cases look identical to oem except for the mount for the gear position sensor right on top of where the engine serial number plate would be found.  The sensor plugs into the main wiring harness that goes to the ignition box mounted behind the front number plate.

The 1997-2001 RC250M's used some magnesium parts.. the factory fork caps, the front master cylinder and 2000-2001 rear master cylinder, the 2000-2001 rear brake caliper, the rear hub, the engine ignition cover, the engine clutch cover, and the engine right-side inner cover.  While light and strong, it is a pain to take care of on a display bike. I have no problems with the rear hub with its original paint, but the ignition cover turns grayish green where I sand down the "Honda Racing" lettering like the factory team did, the front master cylinder oozes white powdery gook where the bare machined surface mates with the cap, the clutch cover is reacting through the Dow coating even with some special gold colored coating under the dow coating. I have to clean/ treat the magnesium parts every 7 or 8 months. Here is a pic of an HRC right side inner cover in great condition, but you can see it is reacting through the Dow coating around the kickstart boss.  The HRC right side inner cover is identical to the OEM cover in every feature except that it is made of magnesium and uses the same Dow coating as the HRC clutch cover.

The picture below shows the longer fabricated lower mount before I drilled and tapped the bolt hole.  Clayton from Trick Engineering did the TIG welding and machining for me.  I highly recommend Clayton..always reliable, professional and does great work. After the welding and machining, Clayton replaced the sight glass and cerakoted the master cylinder "satin mag" to mimic the bare magnesium finish of the HRC prototype part.

It worked out better than I thought. I was able drill the hole dead center by using a short piece of aluminum tubing the exact same diameter as the mounting hole on the frame (12mm) that had a small 2-3mm inner diameter, perfect to guide the drill bit to start the hole.  Looks like it came that way from the factory and I think it would be hard for most to distinguish from the HRC master cylinder unless they were side by side. The biggest difference is the "Nissin" logo is on different parts of the master cylinder. The other differences are subtle.

Here is an actual cast magnesium HRC protype rear master cylinder.  This is the développent part that led to the part found on all Honda production and factory motocross bikes from 2002 to the present day. It has the number "378" on it but not sure what that designates. There were a few versions of this prototype part.. the very first was very blocky and had no branding on it, but following the different versions, you can see what the engineers were thinking. The task at hand for them was to develop an MC was lighter than the old design. Along the way, they decided that their prototype needed a little more fluid volume, so they made the reservoir on the final production part slightly taller than the HRC part, they reduced the size of the head on the cap screws to save a little more weight, and they added little ears to the cap to make it easier to remove. Aside from the HRC part being magnesium, the oem part is more refined.

For anyone who has a 1997-2001 CR and would like to add a new style rear master cylinder, I believe the master cylinder of a 2 stroke YZ should be a direct bolt on.  The YZ part has the longer lower mount and has the same bolt spacing as the Honda. I didn't try mounting it myself, but I have a YZ in the garage and took the measurements. Looks like an easy swap.

There are a number of parts on the 2002+ Gen 3 CR250 that were actually developed on the Gen 2 platform.. the electronic exhaust valve, the complete rear brake system, the TPS Mikuni carb, the design of air holes on the side plates, the pipe hanger, and even the shroud graphics.  All were prototype parts, but my build incorporates many of the prototype mods.

Here is the finished rear master cylinder with the lower bolt hole drilled. The satin mag cerakote helps it look quite close to the original HRC prototype magnesium part. Only a sharp eye would notice the Nissin logo on a different part of the MC, and you would really need to place them side by side to pick out any differences. I am quite happy how it came out and appreciate the help of Clayton at Trick Engineering on the TIG welding and perfect machining.

I am just finishing up the rear caliper set up. As you can see in the pic below, the CNC HRC caliper bracket, which is the same dimensions as the 2002+ OEM CR and CRF brackets, sits, too high on the swingarm and is not aligned with the rear axle slot.

The old bracket guide needs to be carefully removed from the inside of the swingarm. Used a Milwaukee mini-grinder, first with a fiber disc and then with a fine flap disc as I got closer to the metal of the swingarm. Very nerve-racking as you can easily cut into the swingarm and ruin it. Here is the swingarm with the old guide removed.

The new bracket guide (from a 2nd donor swingarm) needs to be TIG welded quite a bit lower on the swingarm, same as the factory did for their prototype..

Before the TIG welding, I did a mock up to confirm exactly where the bracket need to be welded. To help with alignment, I got a piece of metric aluminum flat bar and drilled a hole in the end to mount a steel washer that was exactly the same size as the axle slot on the swingarm. This will be my jig to insure I get the right vertical placement on the swingarm.

Here she is all mocked up and ready for welding. Unfortunately, the HRC caliper guard that I had on the old set up doesn't fit the new caliper and will need to be replaced with a new replica from a 3D printer.

I also am redoing the number plates with the numbers and the font used by the Japan team.  I doing one set with the #2 used by Odagiri in 1999 and another set with the #6 used by Takahama in 2000.  Throttle Jockey was able find me the exact font I needed to replicate the plates. They are also the only decal shop that I know that has the template for the HRC front number plate, as they used to do the graphics for the US factory team in 2000-2001.

One of the parts that gets covered up in the final build is the HRC titanium steering stem. Here is one in all its glory.. it is a smaller diameter than the OEM CR/ CRF big bike stems, but actually the same diameter used by XR600R's and CRF150's.

It took me 4 years of searching, but I finally found the correct HRC titanium knuckle that the Japan team used in 2000-2001. You can see the slight differences between the knuckle used by the US team in 2000-2001 (also same knuckle used for 1997-1999 bikes) side by side with the one used by the Japan/ MXGP teams. Very slight difference in the shape of the outside boss that the lever rests against when it is open and of course the clocking of how it sits on the shaft is slightly different.  These little titanium HRC parts are like jewelry!

I am making 2 new sets of side plates, one with the 1999 green backgrounds and one with the 2000 red backgrounds. The problem I ran into when I ordered new side plates from UFO, was that they changed the shade of the red slightly to a lighter shade of red. I ordered more set searching for so old stock, and I finally found some with the correct darker red. The pile of side plates shown here is only 2/3 of what I just bought. When trying to make a build perfect, sometimes you have to purchase the same item multiple times to get the right one, as things change with these old parts over time.

I have been procrastinating tearing the bike down so I could complete the last part of the build which was TIG welding the frame for the HRC skid plate mounts, the water pump guard and the prototype (at that time) rear brake caliper. The rear caliper bracket guide has to be moved down lower on the swingarm. I also cut a piece of pipe the same width as the engine cases so I could pull in the frame rails before welding. This is necessary to ensure the skid plate holes line up after installing the engine.  HRC welded threaded inserts into the lower frame real for the water pump guard as shown below.  The welding is now done and I am detailing the frame before reassembly.

I do have a bunch of new parts going on the bike for this last stage of the build.  The nos HRC kickstart knuckle was a long sought after part. I also finally found an all silver pair of Renthal bars which I couldn’t find previously. I kept telling myself not to blow money on expensive parts I will never be able to see, but I did pick up an HRC carbon fiber air filter base which has titanium inserts. I will never see it but will keep the HRC titanium air filter bolt company. The factory team also used a Hinson clutch so I bought one of those, too.. kind of foolish for a display bike. Many of the museum bikes in some big museums don’t have any engine internals, which makes good sense.

The titanium tips on the HRC Kevlar silencers are a thing of beauty.. HRC threaded the end of the 6061 aluminum stinger pipe and the titanium tip is screwed on with some white pipe dope and then tack welded in place. The factory team then covered up the titanium joint with an OEM rubber tube, completely hiding this beautiful workmanship.

It has been a full 7 years since I started out intending to build a 2000 Japan RC250M replica but ended up finding enough parts to come close to recreating the original factory machine, short of the engine internals (which I convinced myself would be pointless for a bike that would never be ridden and the parts impossible to see). Nevertheless, for this final round of updates (time to close out this project), I did manage to pick up a few more HRC parts and totally dismantled the bike for a final rebuild to ensure every nut and bolt was the same or as close as possible to the original factory bike that had won so many championships in 1999, 2000 and 2001.

I continued to learn more about the HRC bikes and parts during this final reassembly, and it made me realize how few OEM parts were actually on this era factory bikes even though they looked somewhat similar to the production models. It is rather easy to make up a quick list of the parts that were not created specifically for the Japan factory racer;

--- Frame, swingarm, engine cylinder, cylinder head, right side engine center case, carburetor, air box, and countershaft sprocket protector were all modified oem parts

--- The front axle dust cover, exhaust valve cover, throttle, most of the plastic bodywork, carburetor boots, rear brake clevis and rear axle blocks were unmodified oem parts

That’s about it!  Pretty much all other parts were created anew by HRC specifically for this factory racer. This fact really hit home during this final reassembly.  Here is the Japan HRC carb.. it was an oem Mikuni carb with the choke machined off and passageway plugged, the front of the carb was shortened to improve throttle response and vent canisters were epoxied on to help prevent blubbering on hard jump landings.

I was wondering how HRC fit the shortened carb while using the oem boots, but you can see in this pic below, that they had the rear of the shortened carb half hanging out of the rear carb boot. Not so trick.

The MXGP bikes kept the choke and carb length same as OEM and only added the vent canisters;

The US, MXGP (PAMO) and Japan teams supported by HRC shared quite a few of the same parts, but often did things a little differently.

I couldn’t find a Japan team skid plate, so I mounted a US team skid plate instead. Here is the final install;

The US team skid plate fits between the frame rails and is very clean and light;

The MXGP skid plate is much wider, wrapping around the frame rails to protect the frame;

The Japan team skid plate was the same as the MXGP skid plate with lots of holes drilled in it. Different strokes for different folks;

One of the last parts I found to help complete this build was this NOS HRC titanium kickstart knuckle. It is a small part, but an exquisite piece of jewelry when you get a close look at it;

Here is a cockpit view of some HRC handlebar jewelry. This HRC clutch perch design was introduced in 2001;

Before that, HRC had this simpler design, but it was the start of on-the-fly adjustable clutch levers that are ubiquitous today;

Here is a close up of the NOS Kevlar silencer.. on every HRC silencer I have seen, I noticed that HRC placed the Kevlar weave pattern in precisely the same place on every silencer they made so the cross-hatch design lines up with every rivet and seam identically;

This shot is a good example of how few parts are shared with or would even bolt onto a production CR without a lot of other special parts to make it work. The HRC magnesium hub requires different offset wheel spacers and uses a wider than production 36 spoke rim. I always thought it out of place that HRC anodized the wheel spacers green as if they were trying to draw your attention to all the special parts on the machine.  The rear sprocket is specially machined by Renthal to fit the factory hub.  The hub requires a special 6-bolt brake rotor that requires specially machined titanium bolts that fit into a slot on the rotor. While the swingarm is almost the same as the production unit, but it has the caliper bracket guide relocated lower on the arm to accommodate a special CNC billet caliper bracket.  While the caliper, bracket and caliper guard were prototypes for the 2002+ production machines, the 2002+ oem caliper guard has a narrower mounting pattern than the HRC parts so does not fit well on the HRC bracket.  The caliper and brake rotor guard bolts are aluminum and specifically machined for use only on these 2 parts.  The HRC titanium rear axle has a beautifully machined aluminum axle nut. There is not much left here that is shared with a production 2nd gen CR250;

Most of the bolts on this bike are machined for use only in one spot and unlike the production steel bolts which are used with collars, spacers and washers, the collars, spacers and washers are eliminated on the HRC hardware. Here is an HRC seat bolt and rear fender bolt with the collars machined as part of the titanium bolt. I suppose this made for faster replacement of parts during a race;

The one major part I never got my hands on was the prototype sand cast magnesium rear brake master cylinder, but the replica part I made to look like the prototype master cylinder came fairly close.  I will keep my eye out for the genuine part though;

Lower bar mounts and fork caps are magnesium, steering stem is titanium, Japan team issue fuel tank is slightly larger capacity than oem and uses a bolt-on front mount that didn’t find its way into production until the first CRF;

The remaining pics below are the finished bike.  Nothing more I can do on this build. I am still considering whether I will stick with the green number plates used in Japan until 1999 (#2 was Odagiri’s number) or the red plates that have been used from 2000 to the present day (#6 was Takahama’s number in 2000).  Green is a bit more nostalgic for me as it was the era when HRC had the wildest works parts for their time;

Thank you.. agree it is amazing how much effort put into making special parts for very small incremental gains.

The HRC front number plates are not symmetrical. The upper right hand corner has a different shape than the other three and the sides are not parallel. Also, the Japan factory team was still putting on stick on vinyl numbers on solid backgrounds at least until 2001. I am not sure when they started using fully printed number plate backgrounds. Throttle Jockey is the only mx graphics company that has the template for the HRC front number plates as they made the graphics for the US Honda factory team.

Unfortunately, these trick parts will remain hidden, but HRC used a carbon fiber air filter base that attached with titanium hardware and the filter bolt itself was this welded titanium part.

I believe both the US team and the PAMO MXGP team used Twin air filters, but the Japan factory team used the oem air filter, so just installed an nos oem air filter.