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Many HRC parts are not made by Honda themselves, but made by special design shops to HRC's specifications. The HRC seat was made TS Tech Inc. which I believe designs car interiors and auto upholstery. The HRC triple clamps, clutch perches, shift lever, etc., are all made by other companies for Honda. This is not an uncommon approach in Japan where major companies have many parts made by other companies who made the parts specifically for the Japan giants. This puts more financial risk on the other companies who make the investments in tooling and get hit during economic downturns, but do well during good economic times manufacturing on behalf of the manufacturing giants.
Unlike the OEM seat which has two separate steel tabs riveted to the seat frame to mount the seat to the subframe, the HRC seat has a special steel one-piece bracket to mount the seat. The HRC seat uses the OEM seat materials, but where the red and black vinyl are thermally sealed on the OEM seat, on the HRC seat they are sewn together.
If it’s an RC250M, it has to say “RC” somewhere!
The Shop
The fix I hoped to use was a Pro Circuit Teflon coated billet aluminum throttle tube. It looked nice although a bit pricey. This billet throttle tube doesn't have the ridge so you can slide the Renthal grip on a far as you like.
I ran into a problem, where the throttle would work fine until I tightened up the housing screws whereupon the throttle was very hard to turn. The tolerances of the Pro Circuit tube in the OEM throttle housing were too tight. I spent half a day trying to figure you where it was rubbing and sanding to get a free spinning throttle, but was not successful.
Anyone ever run into this before? I just bought 2 other brands of billet throttle tubes to see if I have better luck with them.
There is also a "California Proposition 65" cancer warning on this PC part (probably because of the Teflon) :O
I have TUSK and a Motion Pro tubes on the way. We will have a nice working throttle in the end with no unsightly gap with the Renthal grip.
Next I tried a Tusk billet throttle tube and that had less issue and it was happy even with the original throttle housing. It has this neat little nylon ring on the inside of the tube that helps it turn smoothly. However, there was one small issue.. if you put a little pressure on the grip towards that housing, it would briefly catch on something and make a little clicking noise that could also be felt. Nothing dangerous, but noticeable and I am fussy about my throttle feel.
Tusk throttle tube;
I decided that nothing feels as good as the oem nylon throttle tube and decided to remove the offending ridge. First I snipper of the much of the ridge with tin snips and then went over to my bench grinder with a 6" grinding stone and slowly and carefully rotated the tube on the spinning stone (slow to moderate speed) until the ridge was gone and completely flush. Came out nice and clean..
Here are the before and after pics.. initially with the Renthal grip installed on the oem throttle tube and you can see in the picture how the oem tube has a ridge the doesn’t allow the grip to quite go all the way on and leaves an unsightly gap. I wonder how many guys ride the bike like this since your right hand would be spaced further out than your left.
Here is the finished job.. the unsightly gap is gone, the grip now is evenly spaced with the left side, and nothing feels as good and as smooth as the nylon oem throttle tube. If I did this to begin with, I would have saved myself $150 and 2 days of frustration.
tube made by Pro Taper. There's no binding but, there's still the gap. It has the ridge that keeps the grip from moving as close as yours is now to the throttle housing.
mike
Over the past week, I was able to pick up a couple of the old style NOS Renthal bar pads. They are a little wider and the lettering is not slanted like the latest versions from Renthal. These old pads are getting harder to find in good condition.
I though I was done with this build, but at the least, I have decided I need to replace the triple clamps with a set of HRC clamps that are period correct. The HRC clamps from 2001 and earlier have chamfered edges, while the newer style HRC triple clamps have rounded edges. Here is a pic of the chamfered edge on the top clamp..
Here is how the bike sits now with the recent changes..
One of the challenges with this build is that many pics of the actual bike raced in Japan have either been deleted, reduced to thumbnails quality, or just plain poor definition. Just recently, 4 videos were posted on YouTube that cover a bit of the 2000 Japan MX nationals together with a lot of coverage of Ryuichiro "Hammer" Takahama and "Yoshie" Atsuta racing and play riding on their RC250Ms. Japan used green number plate backgrounds in 1999 and red backgrounds in 2000 for this model RC250M. Here are some screenshots;
Here is the link to one of the 4 videos..
https://www.youtube.com/watch?v=jaCcKrxT6go&t=400s&pbjreload=10
It's a shame Pro Circuit had the attitude they did toward you regarding the tube. I've had similar issues with other companies and parts claimed to fit an 01 and didn't. Trial and error I guess. Just sucks cause bike parts aren't cheap. Cool video.
Last but not least, if these build threads could be added to the HOF yours should be in it. Not only have you covered the finer details with great pics, you've also shared a lot of history. Sorry for the long winded message. I've just really appreciated this build from day one
Pit Row
Notice how the front brake disc cover attached to this long protruding mount on the fork lug.. while a second disc cover bolt screws into the side of the axle itself.... very different mounting than the oem disc cover. In fact, a lot of special parts are needed to mount this fork on the bike. Special steering bearings and seals that are not easily sourced outside HRC are needed for the titanium steering stem which is narrower in diameter than the oem stem, The works forks require a different brake caliper adapter and a different axle (oem axle will not work). The HRC titanium triple clamp bolts are much shorter than oem and shorter than one would expect.
Notice how the titanium fork lug bolts are completely hollow. It is the only completely hollow bolts on this RC250M.
The HRC front axle is a “floating axle “ set up that is part titanium and part steel. A steel axle threads into a titanium tube which is clamped in the left side fork lug. Very different from the oem setup. Notice the small threaded hole on the outside end of the front axle holder. This is where the HRC plastic brake disc cover bolts to.
The dark-reddish copper colored titanium nitrate coating that HRC used in the lower tubes on the works Showa's is certainly nice to look at.
The HRC titanium triple clamps bolts are very short at just 27mm long. The OEM bolts are much longer.
I also came across this rare HRC billet front brake line guide clamp with Ti bolts. It was used on the late 1990s RCs and early 2000s CRF factory machines even though on the machine I am building, Japan HRC used the oem clamp. I had never seen one before until a friend showed me some pics of them on a few factory Honda's. It is a small piece, but something that is hard to come by as HRC only used them in Japan, I believe.
The HRC exhaust valve cover spacer is quite thick and just barely fits behind the exhaust pipe. They did come in different thicknesses to help tune the power delivery. The thicker the spacer, the smoother the hit and with a broader power band/ increased low end. This one is genuine HRC, but Corné over at Vintage Honda can have an exact copy machined for you if you would like one for your build. Corne is a member on VitalMX.
Post a reply to: 2001 CR250 $pecial Restoration Part II - Recreation of a 1999-2000 Japan Honda Factory RC250M