CHOP CULT HOME
Email Password
Search
  1. #1
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jun 2011
    Posts
    52

    Default Hardtail Install for the KZ750B Twin!

    Howdy from Texas everyone! Haven't been on here in a while so I figured we'd better poke our head in and offer a little eye-candy...

    We were recently offered the opportunity to develop a production hard tail or rather "REAR LOOP" for the legendary KZ750B model. This is the old TWIN that is sometimes elusive to find and fun to chop and a BLAST to ride!!!

    This effort began with Mr. Paul Mader out of Green Bay, Wisconsin who was gracious enough to offer his entire frame as a test-bed for development.

    We are happy to inform Mr. Mader that his KZ750B project has turned out even better than originally expected!

    Here's the install:

    We began with the original frame:


    We were able to design the REAR LOOP to accommodate approximately 4 inches of drop giving us a finished rake of 32 degrees (plus-minus).


    Notice the temporary jig we fabricated in order to accurately design the heavy-duty rear engine mounts. This jig IS NOT NECESSARY for the rear loop installation by the builder! It's simply for design and development purposes... We began by marking our cut line 1/2" from the kick stand bracket and transferred the same mark directly across to the adjacent side.


    Our next cut line was applied to the main backbone 12 inches south of the neck tube. We also transferred the same line across the smaller box frame tubes as well...


    Once the backbone and box frame rails were cut, we then proceeded to clean up the remainder of the small box-frame tubes where they connect at the neck tube...


    This procedure was taken carefully with care NOT to damage the neck tube. It's not necessarily a problem if you slightly scar the gusset or tube are immediately surrounding this area. A 10ga gusset will be welded in place in a later procedure. Because of this, it is NOT necessary to fully remove all the box-frame tube. You can leave any material that is inside the space that will be covered by the new gusset...


    At this point, about two-thirds of the weight has been removed and we are ready to move on to the next procedure...


    We started preparing the cut ends to be welded by sanding the INSIDE and OUTSIDE of the frame rails. We also drilled 3/8" plug holes under the two lower frame rails and on top of the backbone. These holes were drilled about 1/2" from the cut edge...



    Next... We began by sliding the rear loop (MK28) into the KZ backbone. This had to be done FIRST before attempting to fasten the two lower rails of the frame...


    With a mark placed 2" down the backbone, we positioned the MK28 to the mark...


    At the same time, we confirmed that our lower rails had approximately 1/4" of material gap appropriate for a proper weld...


    Once the two units were in position, we checked alignment by taping a string to the TOP CENTER of the original backbone as close to the neck tube as possible. Using this string, we could adjust the MK28 left or right until the string showed accurate alignment down the center of the original backbone and the MK28 backbone as well...


    At this point, we felt it was safe to tack-weld the rear loop in place!


    After verifying that everything was still in place and aligned, we began the final welds. We started each weld at the PLUG location, filling it flush with the surface of the frame rail. Full penetration is important when "plugging" these holes!


    We also laid a "healthy" bead to fill the small gap between the interior of the existing KZ backbone and the new MK28 backbone. As this area rests beneath the gas tank, we didn't worry about the appearance of the weld... We just made sure it would hold!


    After repeating this process at the two lower frame rail connections, we were happily left with a completely modified KZ750 Twin frame ready for the gussets and motor mounts!




    Remember that ENGINE JIG we fabricated earlier? Well... Now it comes into play! Since we do not have the motor in-hand, we had to use our engine jig to design and fabricate the rear motor mounts. They are fabricated from 3/8" mild steel and are more than hefty enough to support the KZ750B! With the motor (or jig) in place, we can fasten the mounts to the motor making sure that the mounts are properly installed with precision. We are letting Paul Mader complete this process since he is still in possession of his motor.


    THE FINAL DETAIL!

    For those of you who wish to keep your steering lock mechanism, this is what we did... We traced one of the supplied neck gussets on a piece of cardboard. We then trimmed the cardboard until it had an adequate notch for the steering lock...


    We then traced the cardboard onto the supplied neck gusset...


    Secured in a vise, we were able to trim out the small notch using the outer edge of an abrasive cutting / grinding blade. You have to be patient and careful not to go outside your lines when performing this procedure...


    With the new neck gusset notched, it is now ready to weld in place!


    And there you have it! We are done with the gussets and Mr. Mader's frame is ready to take a trip from Texas to Wisconsin!


    We hope to see what Mr. Mader does to complete and personalize his 750B build and we will certainly post any update photos soon as we receive them! Thanks again for visiting this thread and if you have any comments, feel free to PM away!

    Cheers!

    David-
    Voodoo Vintage

  2. #2
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Sep 2011
    Posts
    50

    Default

    I have been wanting one of your kits for my CSR soon very soon. Looks great.

  3. #3
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jun 2011
    Posts
    52

    Default

    Quote Originally Posted by royota View Post
    I have been wanting one of your kits for my CSR soon very soon. Looks great.
    Thank you!

  4. #4
    Senior Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jul 2012
    Posts
    831

    Default

    Nice work, but the mismatched backbone diameters just looks un-professional to me. I hardtailed my KZ750 twin and started the backbone off of the headtube.

  5. #5
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jun 2011
    Posts
    52

    Default

    Quote Originally Posted by JamesM View Post
    Nice work, but the mismatched backbone diameters just looks un-professional to me. I hardtailed my KZ750 twin and started the backbone off of the headtube.
    Yeah... But did you build 400 of them? Ha ha ha....

    I understand the visual discrepancy... However, two factors are at play here...

    First: The backbone connection is well under most any fuel tank that anyone will install and should not be visible in the least.

    Second: This is a production product has to be made easily installed with as little room for error as possible. Removing the entire original backbone would require very careful removal of ALL material connected to the head tube except the two existing down tubes. The new backbone would have to be held DIRECTLY on center line with the steering tube and an entire new gusset system would have to be welded in place.

    For someone attempting to do this in their home garage with minimal tooling and no jig, the chances of warping or misaligning the frame components would be great if not guaranteed!

    This is a production product intended to be used by novice bike builders who don't have a large investment in tooling! Anyone capable of correctly welding the backbone straight to the existing head tube (as you suggested) would already be an advanced fabricator with little need for our products in the first place.

    HOWEVER... IN CONCURRENCE... The OEM backbone on the KZ750B is 41mm (1-5/8"). We certainly could (and would) fabricate a custom variant using the exact size material for anyone willing to pay the additional tooling and material charge. It would also require an additional $25+ domestic shipping because of the size envelope.

    Unfortunately, we are always on a balance beam of aesthetics and economics. We have to keep our products within our customers' budget and ability. And believe me... That's why they love us so much!!!

  6. #6
    Junior Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jul 2013
    Posts
    1

    Default

    Thanks Dave!!!!

    This is my frame and I can't wait to mock it up.

    Great job!

  7. #7
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Aug 2013
    Posts
    79

    Default

    looks good, i cant wait until mine gets here. process is pretty much the same for the KZ1000?

  8. #8
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jun 2011
    Posts
    52

    Default

    Quote Originally Posted by pbmax View Post
    Thanks Dave!!!!

    This is my frame and I can't wait to mock it up.

    Great job!
    It's ready to ride man! Send me a ticket and I'll get it on a truck for you ASAP brotha!

  9. #9
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jun 2011
    Posts
    52

    Default

    Quote Originally Posted by Beaner242 View Post
    looks good, i cant wait until mine gets here. process is pretty much the same for the KZ1000?
    It's almost identical! Couple of different measurements and the backbone of the KZ1000 is tremendously SMALLER than that of the 750Twin!!!, so you don't get that rather large transition...

  10. #10
    Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jun 2011
    Posts
    52

    Default

    By the way... We ship the MK27, MK29, MK23, and MK22 with the backbones strapped inside the hard tail.
    This is done because with the backbone in place, FedEx, UPS, and DHL will charge the same amount as shipping a FULL motorcycle frame!!!
    This method will save an average of around $25 to $30 for domestic shipping...

    The installer needs to assemble the backbone into the hard tail before grafting the entire unit to their original frame.

    Although this video is intended for the Model 27, it can be applied across the entire range of hardtails shipped without the backbone fully installed.


  11. #11
    Senior Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jul 2012
    Posts
    831

    Default

    Quote Originally Posted by voodoovintage View Post
    Yeah... But did you build 400 of them? Ha ha ha....

    I understand the visual discrepancy... However, two factors are at play here...

    First: The backbone connection is well under most any fuel tank that anyone will install and should not be visible in the least.

    Second: This is a production product has to be made easily installed with as little room for error as possible. Removing the entire original backbone would require very careful removal of ALL material connected to the head tube except the two existing down tubes. The new backbone would have to be held DIRECTLY on center line with the steering tube and an entire new gusset system would have to be welded in place.

    For someone attempting to do this in their home garage with minimal tooling and no jig, the chances of warping or misaligning the frame components would be great if not guaranteed!

    This is a production product intended to be used by novice bike builders who don't have a large investment in tooling! Anyone capable of correctly welding the backbone straight to the existing head tube (as you suggested) would already be an advanced fabricator with little need for our products in the first place.

    HOWEVER... IN CONCURRENCE... The OEM backbone on the KZ750B is 41mm (1-5/8"). We certainly could (and would) fabricate a custom variant using the exact size material for anyone willing to pay the additional tooling and material charge. It would also require an additional $25+ domestic shipping because of the size envelope.

    Unfortunately, we are always on a balance beam of aesthetics and economics. We have to keep our products within our customers' budget and ability. And believe me... That's why they love us so much!!!
    Yeah, I get that... definitely makes sense from a production standpoint. Glad you are able to take a little constructive criticism without flipping off the handle like most people.

    Continue the good work, I dig a lot of what you guys do.

  12. #12
    Senior Member

    Content on this page requires a newer version of Adobe Flash Player.

    Get Adobe Flash player


    Join Date
    Jan 2011
    Posts
    563

    Default

    yeah dude the way you answered that question makes me want to do business with you and i don't even have a kz 750 twin


    good work man.

Share This



Tags for this Thread

Posting Permissions

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

Log in

Log in