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This is a discussion on xs750/850 within the Project Builds forums, part of the Caferacer.net Forums category; Can you drill a hole that will go all the way through and weld a bung/stud from both sides of the stamped steel section ? ...

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  1. #21
    Senior Member Ravivos's Avatar
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    Can you drill a hole that will go all the way through and weld a bung/stud from both sides of the stamped steel section ?
    if so, you will not reduce the structural integrity of the frame and have a very solid mounting holes for the reasets...

  2. #22
    jcw
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    Yeah. I'm worried about warping the frame and I don't want to go through the trouble of building a frame jig, you know.

    That would be the most solid mount though...

  3. #23
    Banned Witworth's Avatar
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    Quote Originally Posted by jcw View Post
    I look forward to getting the engine together and starting it up for the first time with those carbs.

    If a dyno is not a datalogger, what is it then? Getting the A/F ratios in-the-ball-park would be my primary goal with the datalogging. Whether that's done on a stretch of flat road or on a dyno makes little difference to me. There are differences, but little.

    There's a lot of calculators out there for calculating primary diameters. I've tried about 4-5 of them and get a "wide" range of diameters. Ultimately, I'm looking for primaries that are small enough to maintain exhaust gas velocity without choking the gases coming out of the head. I think I'll touch up the stock headers then weld up one the "next size" larger. I've got a stock system from a 1976. It's pretty heavy being double walled and at the connection points, the pipe is choked down to less than 1" with reinforcement. But it's got a gorgeous shape. About 1.12" ID which coincidentally is close to what I've been getting with my calculations. Start with that and move up from there.
    Forget exhaust calculators. Good for guys who spend thirty grand on euro Honda Civics to race for sody pop.

    Dynos are controlled conditions data loggers. You riding around with a exhaust gas sensor never will be "in controlled conditions".

    Go for 1 inch header tubing. 1 point whatever is too big.

    Forget drilling or welding near the highly stresses swingarm pivot point.

    Pressed metal sections are often stronger that any made by barn job mechanics. Why they have a rep for cheapness, is beyond my understanding.

    Danger, is my business."
    Last edited by Witworth; 07-20-2015 at 06:13 PM.

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  5. #24
    jcw
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    Quote Originally Posted by Witworth View Post
    Forget exhaust calculators. Good for guys who spend thirty grand on euro Honda Civics to race for sody pop.

    Dynos are controlled conditions data loggers. You riding around with a exhaust gas sensor never will be "in controlled conditions".

    Go for 1 inch header tubing. 1 point whatever is too big.

    Forget drilling or welding near the highly stresses swingarm pivot point.

    Pressed metal sections are often stronger that any made by barn job mechanics. Why they have a rep for cheapness, is beyond my understanding.

    Danger, is my business."
    One of the smartest engine guys I've had the privilege to listen to built some crazy Honda heads. Before that he was an engine builder in the 1970's and 80's for NASCAR and was one of the first to utilize super high compression, high swirl, lean burn combustion chambers. Larry Widmer.

    The Old One - Energy Dynamics

    Read about his Grand Sport Corvette. I know nothing about that car, but damn it looks sweet.
    Look at the Facilities link.
    read some of the articles.


    Speaking of pressed streel frames...
    Name:  ks600.jpg
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    As for the xs750, they went to a different design on the xs850 with more welded and gusseted tubing to the swingarm pivot rather than the pressed steel. I presumed this was stronger but admittedly have not tested it. I've read Tony Foales stuff on motorcycle frame bending jigs and frame bracing.
    Last edited by jcw; 07-20-2015 at 11:17 PM.

  6. #25
    Senior Member hillsy's Avatar
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    Don't know if I'm stating the obvious for you here but whatever method you use to mount your rearsets just make sure you don't cover up / block / foul the swingarm bearing recesses.

  7. #26
    jcw
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    1" OD 16 gauge is only .88" ID.

  8. #27
    Senior Member hillsy's Avatar
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    Quote Originally Posted by jcw View Post
    1" OD 16 gauge is only .88" ID.
    Which for an exhaust is tiny. Measure the ID of the headers in your 1st pic. They're probably about 1.5" ID.

  9. #28
    jcw
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    Quote Originally Posted by hillsy View Post
    Don't know if I'm stating the obvious for you here but whatever method you use to mount your rearsets just make sure you don't cover up / block / foul the swingarm bearing recesses.
    Yeah. I'll use the metal legs that go back from the swingarm pivot and leave that section alone. Weld up something there.

    Probably trash the whole adjustment mechanism and maybe even just use the peg and arm themselves on a single bolt mount. The more I look at it, the more it screams NO DON"T DO IT.


    If I did mount it over the swingarm pivot, the rearsets would have to be unbolted to get to them. But they wouldn't have been inaccessible.
    Last edited by jcw; 07-20-2015 at 11:07 PM.

  10. #29
    jcw
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    Quote Originally Posted by hillsy View Post
    Which for an exhaust is tiny. Measure the ID of the headers in your 1st pic. They're probably about 1.5" ID.
    They look big but they are double walled. ID measured about 1.12" but at each end of the header pipes, there was an internal reinforcement ring that choked the diameter to just under 1". Really quite nicely made stock exhaust other than that small detail.

  11. #30
    jcw
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    I hope I didn't fuck myself with ground clearance issues.

    I really don't want to have to lift the engine in the frame.
    Last edited by jcw; 07-20-2015 at 11:19 PM.

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