Spanking the Cow- The continuing saga of an R100GSPD at the Races

Discussion in 'Airheads' started by Stagehand, Jan 20, 2011.

  1. Stagehand

    Stagehand Imperfectionist

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    I was wondering the same thing!

    I personally couldnt tell a majotr difference between my R100 and Paul's bike--


    WHen I say I couldnt tell a difference, I mean of course I could, they were amost Entirely dis-similar but i mean that i did not miss 130cc by a long shot.

    The engine pulled long and hard, for as long as my courage held out.

    And it seems shortsighted to simply put up with the extra two inches of width and whatever extra weight came with the R100 motor, even if it is easier.

    Hows this for an idea:

    SInce the short width of the R65 stems from the short con-rods, and one is required to shave the cylinder bases down anyway, is it feasible to simply put short con-rods in an R100? With short headed pistons, (JP's?) one should be able toget he same volume out of the jug... I doubt it, I bet the conrod bores are the wrong size, it would be a custom con-rod deal. Maybe thats ok?
    Then there's making the pushrods do right. Use R65 pushrods?

    Paul is not unenlighted to solve for the lightest combination possible. Everything we talked about, he was stressing lightness.
  2. Airhead Wrangler

    Airhead Wrangler Long timer

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    Are the rods much shorter? I thought it was mainly just the shorter stroke of the crank that made it a narrower engine.
  3. Rucksta

    Rucksta SS Blowhard

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    Finger fault or brain fart not sure which.
    Sorry AW and appologies to SH no intention to discount your achievements in the Safari. great effort.
  4. Rucksta

    Rucksta SS Blowhard

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    SH

    15mm shorter conrods are available from a number of sources including Carillo
    Not cheap and neither are std BMW con rods.
    30mm overall width reduction and the changed intake characteristics look appealing.
    The modification is not unusual on road race airheads.

    I've also wondered if short top / short skirt pistons designed for a longer rod combined with a shorter rod an cut down barrels would result in a 60mm or better than 2" narrowing.
    Whether the piston skirt extends past the end of the barrel at BDC and the increased angle of the conrod clearing the barrel end at half stroke wouild seem to be important.

    Once upon a time I might have tried it.
    I find the width of the 980 motor not so much of a burden that I want to throw $$ at it just to slim it down. It is rare that I need to be one inch closer to the edge of the track and the inch less still doesn't get the bike flat enough on the ground to get it under the gates they use on forestry tracks around here to keep the 4x4s out.

    Maybe at rebuild time when I need to replace barrels pistons and conrods I will also feel like adding an amount equal to the parts cost to do the mods to slim it down. I'd be looking at $4.500.00 - $5,000.00 plus new headers and some more for unexpecteds.to have Paul Rooney or Ray Peake do the work using new parts.

    I believe I could have picked up Rays 860 motor complete for under 5.

    It may be cheaper where you live.
  5. gsd4me

    gsd4me 90% bluff

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    Pity it`s already sold. It sat around for ages now people want it. :lol3
  6. Rucksta

    Rucksta SS Blowhard

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    I didn't really want it but was very interested in the technology and mods he did.
    Sort of hoped he was going to do a full on dirt bike with it and come an play on the side of the volcano ocassionally
  7. RealOldDualSportGuy

    RealOldDualSportGuy Long timer

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    Any suggestion as to tires for the Sand Blast rally?

    Stage Hand has us "hooked" on rallying in the sand come spring.

    Any and all assistance/input is appreciated.

    Regards

    Blame It on Stage Hand

    :norton
  8. Stagehand

    Stagehand Imperfectionist

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    Tom!

    I was just thinking about you, today.

    I recommend D606's. They're DOT, (which is technically required byt he rules :deal) and they have good sand bite (when they're new) and they're relatively cheep and they are made in a 17 and an 18".

    My personal preference.
  9. AntonLargiader

    AntonLargiader Long timer

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    A bit (4.5mm?) of the narrowness also comes from the shorter stroke. For a high-RPM motor I suspect short rods with regular stroke is a bad idea. The narrow race motors of the '70s used extreme pin location in the piston. On some (or all) you had to remove the rings to get the pin out. There is one such motor about 100 miles away; I should go check it out.

    I think the mix 'n' match logic goes like this: if you want the shorter rods you need the shorter stroke. Once you have the heads closer to the crank you might as well use the R65 block for better pushrod angle. Therefore, use the whole R65 bottom end. The problem with that (in the old days at least) has been the lack of cam selection, and I think some vintage racers are using the R65 setup in R100 blocks and just accepting the funky lifter angle.
  10. RGregor

    RGregor Been here awhile

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    They also used 125mm rods (Butler & Smith and Helmut Daehne for example). That's minus 10mm each side.
    Gives about the same rod-length ratio like in the oilheads.
    I would think the 118mm rods of the small blocks would be a bit too extreme in combination with the long stroke.

    In the meantime Schleicher offer a variety of cams (from 320° to 344°) for the small blocks.
  11. Owly

    Owly Into the Dark

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    I read that Helmut Daehne's bike with the shorter barrels, the engine was taken off the production line and where the push rod tubes go into the block, that the block had to be machined to allow for a steeper angle on the shorter push rods.

    But i am no expert engine builder.. Just a reader
  12. Stagehand

    Stagehand Imperfectionist

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    Here I am wondering if its more manly to build a damn bike and race it and knowing me that is a dodgey prospect, the build part) rather than just get a hold of one any way I can. And go race it. Especially listening to you guys talk tech, god I am forty years old there isnt enough time in the day to take in all this info, I should have started back when I was just a kid, instead of this whateverthehellitisIdo, The race, I now realize is all about the suspension. Tied with reliability.
    Good old reliable R100? or hotted up 650 with shaved private parts and an unfamiliar cam stuck in its hoo ha.

    Ooo but the little hottie is tempting. Should I waste my time building it? Or have somebody build most of hte damn thing and I just put my resources into fixing what i break out in the bush?
  13. igormortis

    igormortis Cafe Reise

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    Well, I guess you've worked on Rider for a bit. Now do Chassis. When you can't go any faster, build a stonking Engine.
  14. Rucksta

    Rucksta SS Blowhard

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    Rolling Chassis aint that hard.
    Running gear and adding the elusive lightness is the hard part.

    Weight loss from the motor is minor compared to other areas of fat.
    Engine weight loss is an expensive chase usaully combined with increasing the performance.

    Like you said. You have enough power already.

    P.S. Forty is young but it doesn't last much longer
  15. Prutser

    Prutser Long timer

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    On a picture that was put on airheadsdown under fb. (on the MX track)You really tried to snap the bottom shock mount.
    How much problems do you have with the suspension ?
    The travel in Paul's bike must have been great. But would you mind to have your bike that tall when doing single tracks with technical sections ?
  16. hardwaregrrl

    hardwaregrrl ignore list

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    I know where you can get a bike that's halfway there!:deal

    <a href="http://s814.beta.photobucket.com/user/hardwaregrrl/media/FFE78E73-ED45-406D-9C21-E814490FCD51-6038-000008CCC08E83C5.jpg.html" target="_blank"><img src="http://i814.photobucket.com/albums/zz66/hardwaregrrl/FFE78E73-ED45-406D-9C21-E814490FCD51-6038-000008CCC08E83C5.jpg" border="0" alt="Uploaded from the Photobucket iPhone App"/></a>
  17. Rapid Dog

    Rapid Dog bikes, booze, broads...

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    :ear:ear:ear
  18. Stagehand

    Stagehand Imperfectionist

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    Lol! I know that bike!
  19. hardwaregrrl

    hardwaregrrl ignore list

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    nathan mende has it. Has had it for almost a year. Rebuilt the trans, the carbs, and a new clutch. After all of that, he's asking 4500 I think. That's why it hasn't moved, but it is a damn blast to ride! I want the bike, but can in no way afford it right now. If anyone is interested let me know. I've tried to sell it for him, just not here for fear of being flamed.:kboom And I will say, I've tried to convince him to let me race it at Sandblast:evil.......but he wasn't going for that one.:D
  20. Stagehand

    Stagehand Imperfectionist

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    How low does it feel in the rear? I always thought it needed a longer swingarm, it just doesnt have it yet :D

    That might be a good start, though, get it back up in NY where it was born, prodigal son returns, etc


    Adding lightness :D I love that

    One more week of Nutcracker, then I see about what we can do with the monster/mistress already waiting down there. Lets maybe just trail ride that once or twice and see?

    Paul says I should maybe buy a race bike from him, come down to the Safari again, and take advantage of the race org's free shipping to get it back home. :evil That sounds pretty efficient in all ways but financially :D