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Honda RS125 + CRF450X = ?...

Discussion in 'Projects' started by Alanjtc73n, Jan 4, 2011.

  1. Got the shiny track princess up on her stand. Even though this track season sucked with 3 rain days, we did have one great day where she got to stretch her legs. At least she got enough miles this year to warrant another top end.


    And her other side.


    And one more of her getting ridden.


    And so it was a fun summer. Great friends. Fun at the track. Learned a lot. But winter is here now. Yes, skiing is fun but winter motorcycle projects can be fun too. A great way to wait out for powder days...and a great way to blow cash...:tard:

    Summer on the CRF450X was also tons of fun. So much fun that I don't got any off-road pics.


    But it did make it to Pacific wearing new wheels and rubber.


    It was damn near perfect for the two rain days that actually ran.
    So I guess this is more of a place holder for now. I've nestled the two bikes next to each other and threw a blanket over them. I left the radio on smooth jazz and a bottle of red wine on the work bench. I even went as far as to take the upper off the 125...I know, it's a little forward but I have to make this happen. I'm headed on a ski trip tomorrow night so these two have the rest of the week to get to know each other. They've got a lot in common. Both were engineered by Honda. Both went to the track this summer. Both like new rubber. Etc.

    Maybe they'll fall in love and put this:




    Or it's all just wishful thinking. Right now I'm in the planning and feasibility phase. I know it can be done but for me the price has to be right...and it's not gonna be cheap. I get to partner with Richard Wascher to engineer the fitment. He's excited and believes that anything can be done if we throw enough money at it. I'm gonna try to prevent that from happening. My other complete bike is at his shop getting the front forks tweaked back properly. He's also got my spare frame. Starting next week the CRF will get torn down and measurements will begin. The spare frame will have the front engine mount spars removed and the area beefed up. Once we get that far, Richard and I will have "the talk" to establish a budget and what realistically must be done to get the project rolling.

    I'll try to keep up with the pictures of the build and it's progress if anyone is interested. For me I'm just hoping for a fun track bike. For Jared, an Open Singles cheater bike. Who knows...with the electrical system, it may even be possible to register it as a homemade motorcycle. Wish me luck!
    Last edited: Jan 4, 2011
  2. Nice post and pics..... and about the RS125...... sooooo jealous :mrgreen:

  3. nice alan!!!!!!!!!!

    i sure hope they start making babies to. unfortunently since they both like new rubbers it might not happen :(
  4. Find Cedric Smith. He did the same thing about 5 years ago and has cleaned up in OMRRA. He'll have all of the info that you need/want.
  5. A little different but kinda the same, Mark Hatten shoved an XR600 into a TZ250 frame some years ago and tore UP the Sounds of Singles Championship 4 or 5 years running.
    It was built by Bare Bones in Denver.
  6. I've kicked around this idea since 03 but never had the money or means to do it. Back in my WERA days in Clubman actually building your race bike was all the rage. But since we had to do it on the cheap it was usually a Hawk or FZR400 chassis. Then came along another novice who had is dad put a Yamaha 660 into an TZ frame...complete with reverse! That thing cleaned up!

    A TZ250 frame would make this project so much easier. But it would defeat my purpose in two areas. First, I wanted to make it as small and compact as possible. Second, I have an RS and CRF in my garage. One of the reasons I hesitated so long is the cost of components. I cringed at the thought of hacking up a perfectly good RS125. Then came the economy. Used RS's aren't worth what they once were. I'm never going to get what I have into my bikes back out, even though I got great deals on them. To give you an idea - an RS frame is $1309 from Honda new. A used one a couple years ago would sell for about $400. Last week I grabbed a used frame for $100. Rather than sit and watch my bikes depreciate, I figured it was time to put those parts to good use.
  7. parent's didn't love me enough. All I got was a yellow pw50. Oh, let me correct that. A yellow pw50 for me and my brother to share.

    Thus my desire to live out my childhood dreams in midlife. Next up - I'm gonna eat brownies for every meal for a day. Wait till I get to adolescence...

  8. I completely understand. My point was to possibly get hold of the guys that did that bike. I'm sure they have a ton of good advice.
  9. Don't get me wrong, I appreciate the tip. In fact, I'll appreciate all the tips as this project progresses. The most expensive part of this project isn't going to be the welding, it's the engineering.

    Funny you mention Bare Bones Machines in Denver. I'm in Denver today but unfortunately won't be stopping by to pay them a visit.

    The problem with these types of builds is that most of the "commercial" builders have spent many man hours to complete their projects. These man hours translate into engineering dollars that they'll only recoup if another customer decides to go through them to do a similar build. Builders like Speedwerx and Aaron Hammel would be reluctant to give up their secrets since they'd prefer it if I went to them with the build instead of doing it locally.

    On the other hand, I haven't tried calling them to find out. Mostly because I don't like rejection.

    In speaking with Richard, I'm technically taking one for the team. Once we get this one engineered the second one will be cake and much cheaper. I'm confident in his ability to work this one out. His attention to detail is ridiculous. Just at our first meeting he started to go off on drive sprocket to swingarm pivot angle. In all my research, I haven't found too many blogs or write ups on these singles conversions. Especially conversions involving the 125 frames. That's why I wanted to post this up. To keep a record and to help others who may decide to go a similar route.

    There's going to be much more stuff beyond the engine stuffing to fabricate. I'm hoping that once the main stuff is done, the good ole forum may offer tips on how to solve upcoming issues.
  10. jnicola

    jnicola Shredical

    I guess if its for track use the fact the CRF450r's online hold 3/4 of a quart of engine oil isn't such a big deal. Just dump the engine oil every other (if not every) session and swap it out.
  11. theJrod

    theJrod Racer Extraordinaire

    Dibs on the test flight.

  12. PeteN95

    PeteN95 Moderator Staff Member

    .75 quart in the engine and another .65 in the transmission, they are separate on the CRF. FYI
  13. Google "CR450f cafe racer" or "CB450f cafe racer"

    Guy's building kits for 'em, not bad looking, maybe give you some more ideas.
  14. Finally got a break in work to take the CRF apart. I don't know how some people break these bikes down just to polish the frame or something. Putting the thing back together would suck. Let's hope this project goes well and I won't have to put the motor back in the frame.


    The frame: Getting the motor out was pretty tricky. I had to tilt it forwards and the rotate right and it finally came out almost horizontal.


    Swingarm, radiator, and some other stuff I won't need:


    And some rolling bits and springy bits:


    I'm off to drop off the motor and frame tomorrow and discuss feasibility. The motor itself weighs just over 71 lbs. I haven't pulled out the RS motor yet but the whole bike weighs 160 lbs. If I end up with a total bike weight under 180, I'll be happy.
  15. Went to the frame shop to tear down the spare 125 and do initial measurements. Current to be done list:

    1. Cutting right and left frame spars
    2. Ream rear engine mount to 20mm
    3. Cut and box swingarm to inlet for engine
    4. Fab central engine mount
    5. Fab front engine mount
    6. Modify waterpump outlet
    7. Fab exhaust
    8. Locate electronics
    9. More stuff but I can't think of it yet

    Easy peasy right?
  16. So the motor had to modified more than expected. The kickstart spline and gears were removed. Then the cover was cut and relieved for more clearance. Not my preferred route but it looks like the only option with the way the frame fits for sprocket alignment.


    Frame spars were cut off and the welds ground smooth.



    The engine height has not yet been determined. Gas tank clearance will be an issue. The relief for the oil fill seems a little drastic but internal ribbing of the frame should compensate. In addition, a rigid mount will be fabricated for the central motor mount to help with torsional rigidity. May go back and lower the engine more and remake the relief cut so that it isn't so far up.


    Swingarm was boxed out as was the rear cross section tube in order to fit the back of the motor.


    Then all the cuts will be buttoned and cleaned up. After that tank fitting will begin. So far so good.
  17. Got a PM requesting an update.


    It runs...well...very well...

    I'll throw up some more pictures with the build progression in a a few days.
  18. theJrod

    theJrod Racer Extraordinaire

    I can say that the little guy likes to wheelie.
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