Budget Parts-Bin Bultaco
Close

Budget Parts-Bin Bultaco

This is a discussion on Budget Parts-Bin Bultaco within the Project Builds forums, part of the Caferacer.net Forums category; Since someone asked, "Building a bike from scratch, worth it?" elsewhere on this forum ( http://www.caferacer.net/forum/gener...tch-worth.html ), I thought I would start a build log ...

Page 1 of 28 12311 ... LastLast
Results 1 to 10 of 278
Like Tree27Likes

Thread: Budget Parts-Bin Bultaco

  1. #1
    Senior Member Tanshanomi's Avatar
    Join Date
    Sep 2009
    Location
    Kansas City
    Posts
    1,391

    Budget Parts-Bin Bultaco

    Since someone asked, "Building a bike from scratch, worth it?" elsewhere on this forum (Building a bike from scratch, worth it?), I thought I would start a build log on my own budget scratch build. Okay, so at this point it's not anything that could even be called a "build." It's more like "holding spare parts up to each other," seeing how they might someday be part of a functional motorcycle.



    In this picture:
    Frame — 1977 Bultaco Pursang 370 Mk10 Model 193
    Swingarm — 1976 Yamaha YZ125
    Fuel Tank — Early '60s Rex KL35
    17" Rear Wheel & Axle — 1981 Suzuki GS450T
    19" Front Wheel & Axle — 1980 Suzuki GS850

    I also have a few more assorted smaller bits around the garage.

    This all started almost six years ago with the swingarm. I saw it on eBay and I thought, "hmm, that would make for an easy monoshock conversion," So I bought it for $23 shipped, without any sort of clear use for it other than for "something...someday." I next got the matching Suzuki star-spoke wheels from two different guys locally, and they reminded me of an old concept drawing I'd briefly toyed with about 16 years ago for an old Pursang 360 parts donor...



    My old Buls are long-gone, but I've been pining for another one. Once I stumbled on this late-model frame, enough of the ingredients were present for me to start envisioning a monoshock Bultaco streetbike.

    Don't expect lots of frequent updates, but I'll post here as I slowly continue developing the project. Since this is strictly a toy, my cost-control strategy is to wait and slowly acquire suitable parts that show up on Craigslist or Ebay for remarkably cheap prices...but I'm already getting excited enough about this to become an impatient hunter. I currently have a line on a pretty 4-speed 250 Matador motor and a 175 Alpina 5-speed, but both are more than 200 miles away.

    ...patience, my boy. Patience...
    Last edited by Tanshanomi; 12-26-2012 at 10:49 AM.

  2. #2
    Senior Member Geeto67's Avatar
    Join Date
    Oct 2005
    Location
    Columbus, Ohio
    Posts
    22,334
    well....it is interesting and it isn't another cm/cb400T.....so get to work - could use an interesting bike to look at being built.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.

  3. #3
    Senior Member joe1028's Avatar
    Join Date
    Jan 2010
    Location
    inver grove heights, mn, USA.
    Posts
    546
    six years for that! hell i don't think i will live to see it finished...ha ha
    i like the look-a modern metrella
    joe

  4. Remove Advertisements
    CafeRacer.net
    Advertisements
     

  5. #4
    Moderator joe c's Avatar
    Join Date
    Mar 2002
    Location
    , , Turkey.
    Posts
    13,809
    subject deserves a star anyway.....
    not a pretty boy honda rider... i\'m fag on a TTR

  6. #5
    Senior Member Tanshanomi's Avatar
    Join Date
    Sep 2009
    Location
    Kansas City
    Posts
    1,391
    quote:Originally posted by joe1028

    six years for that! hell i don't think i will live to see it finished...ha ha
    i like the look-a modern metrella
    joe
    Well, I hope *I* live to see it finished! Actually, I really didn't think about building something much at all for most of that six years. I only got the frame a little over a week ago. Now that that gives me a more specific direction to head in, I'm going to devote some more effort and resources to it. I picked up a front end yesterday and I'm waiting for a monoshock I bought off Ebay to arrive.

    And thanks for the encouragement so far, guys. I'm not sure quite what I'll end up with, but my intention is that, even though this will definitely be a budget build, it won't be silly looking or a bodge job.

  7. #6
    Senior Member Tanshanomi's Avatar
    Join Date
    Sep 2009
    Location
    Kansas City
    Posts
    1,391
    I changed the topic name to "Budget Parts-Pin Bultaco." The original name, "Creatively Placing Parts In Close Proximity," was neither as clever as I thought it was at the time, nor explanatory in any way to people skimming the build topics.

  8. #7
    Senior Member Tanshanomi's Avatar
    Join Date
    Sep 2009
    Location
    Kansas City
    Posts
    1,391
    Here's a crappy scan of another bike that inspired my project. It's a Montesa bitsa built by Jared Bates, owner of Southwest Montesa. I saw the bike at Lynn and Dorothy Mobley's Minden Classic and European Motorcycle Show way back in 1992. Wonder if he still has it?


    There are much better photos it in this guy's flicker stream:
    http://www.flickr.com/photos/az-johnny/5736794448
    http://www.flickr.com/photos/az-johnny/5736796486
    http://www.flickr.com/photos/az-johnny/5736793978

  9. #8
    Senior Member Tanshanomi's Avatar
    Join Date
    Sep 2009
    Location
    Kansas City
    Posts
    1,391
    My first goal for this project is to have a rolling chassis I can push around the garage by the end of the year. To that end, I've picked up a GS650L front end. But lots of things are dependent on lots of other things —*rake and trail are dependent on fork length, which also affects ride height, which is also determined by the choice of rear shock and how that's mounted, etc...

    So, I'm starting with the most basic task, attaching the swingarm to the chassis. The YZ125C swingarm may be nicely braced and ready to accept a high-mounted monoshock, but it has one major drawback that makes it a less-than-ideal choice: it uses a really wimpy 12mm swingarm pivot bolt. I initially played with the idea of going with a larger diameter bolt, especially when I discovered that the 15mm Suzuki front axle I have is just the right length for the Bul frame (which is about 27mm wider at the mounts than the swingarm). But the ID of the swingarm's mounting tube is only slightly less than 24mm, so there's just not enough room to go thicker on the bolt. If I used a 15mm bolt, the inner and outer bushing surfaces would have to be no thicker than 12 or 14 gauge sheetmetal to fit in there. Wafer-thin bushings would be no better than the skinny bolt. So, I'm stuck with a 12mm bolt and the stock Yamaha nylon bushings. Realistically, that shouldn't be a problem. I'll most likely end up with a motor that doesn't put out too much more than the YZ's original 18 HP, and street use won't stress it like banging hard landings off whoops and doubles would.

    The Bul originally used the swingarm pivot for the rear motor mount. Considering the skinny pivot bolt I'll be using, and the fact that the Yamaha swingarm would have to have a gap cut out of the center to accomodate it, I've decided to let the swingarm design dictate alternative engine mounting, rather than the other way around. After all, I have yet to even determine exactly what engine is going to power this thing. (Like I said up top, every decision affects another decision down the line, so the order you do things makes a big difference.)

    I am, however, now presented with a separate issue —*the swingarm mounting holes in the Bultaco frame are 14.3mm in diameter.


    So, how do I "drill them smaller" to center the pivot bolt? Several people have said, "make up spacers," but don't think collars 1.15mm thick and as wide as the mounting plates are a practical option. I could weld up the hole and then drill it out to the proper size, but how do I ensure the two sides stay in alignment? Like most guys, I don't have any high-accuracy stuff like a jig or machine tools.

    Right now I'm thinking that I could weld a pair of proper diameter washers to the frame on either side of the mounting holes. I don't have to center the pivot bolt in the existing holes, I just have to keep it aligned horizontally in the frame. So I could simply install the washers on the pivot bolt and let the bolt rest on the bottom of the holes in the frame while I welded them. (Note that the gap is at the top in the diagram below.) Once I torqued the pivot bolt down, I'm assuming that there'd be a lot of compression friction keeping things in place, so that the welds wouldn't bear too much of the stress directly.


    (To Scale)

    This all seems workable, but I'd like to get feedback on two things:

    #1: Is my washer idea any good, or is there a better option? How thick do they need to be? Could I get by with only welding them on one side?
    #2: Where do I source a strong 12mm bolt about 230mm long?
    Last edited by Tanshanomi; 12-26-2012 at 10:55 AM.

  10. #9
    Senior Member Tanshanomi's Avatar
    Join Date
    Sep 2009
    Location
    Kansas City
    Posts
    1,391
    Well, duh. Just writing this up made think of something I had not considered: using the Suzuki axle as a pivot bolt and simply having it turned down to 12mm —*the threaded portion is already necked down as it is.


    I could simply use an expanding reamer to enlarge the right side frame hole to fit the axle's original diameter, have the spacer made up with a 15mm bore, and have the axle turned down far enough along its length to accomodate the swingarm. I'd have to take more care to make sure that I welded the washers onto the other side of the frame in the proper alignment, but I am thinking a few 90-degree magnetic holders and some careful measurements with a calipers before I weld should get me there.
    Last edited by Tanshanomi; 12-26-2012 at 10:55 AM.

  11. #10
    Senior Member Kurlon's Avatar
    Join Date
    Sep 2009
    Location
    Waterboro, Maine, USA.
    Posts
    681
    Rather than a pair of washers on the right, why not another spacer like the left. 12mm ID through out, say 20mm OD, necked down to 14.5mm (or bigger if you're up for reaming the frame anyways) OD to pass through the frame. Reinforce the frame with a new washer on the outside with the ID set to match the OD where it passes through, trim the necked down portion of the spacer so the nut seats against the new washer before running out of thread or hanging up on the spacer? That way you don't have that small void that is currently present between the washers.

Page 1 of 28 12311 ... LastLast

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Similar Threads

  1. budget dunger (cbx750fe)
    By engel in forum General
    Replies: 7
    Last Post: 12-17-2011, 12:53 AM
  2. kz 440 cafe budget build
    By overthetop in forum Project Builds
    Replies: 27
    Last Post: 12-15-2011, 07:01 PM
  3. Bultaco Campera Parts
    By lastman in forum Wanted
    Replies: 1
    Last Post: 08-29-2010, 07:05 PM
  4. Building a low budget trike.
    By oneworden in forum General
    Replies: 1
    Last Post: 06-04-2010, 10:45 AM
  5. Budget Cafe CB350K-4
    By tshaw151 in forum Project Builds
    Replies: 5
    Last Post: 04-22-2010, 07:40 PM

Search tags for this page

atv shock spring compressor
,
atv shock spring compressor tool
,

atv spring compressor

,
buell blast shock
,
building bultaco cafe racer
,

bultaco cafe racer

,

bultaco parts

,
bultaco pursang head stem bearing part number
,
homemade spring compressor
Click on a term to search for related topics.