/5 Gs

Discussion in 'Airheads' started by storymitchell, Sep 7, 2004.

  1. storymitchell

    storymitchell Member of the proletariat

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    I belong to a vintage BMW club, and recently one of the members was reminising about a buddy that "GSed" a /5 back in the late 70s. Apparently there is a Suzuki dirt bike front end that is a perfect match for a /5 steering head. Has anybody here heard of this? I'm looking for a winter project, and I'm either going chop a /5 or /6, or "GS" one. Any thoughts on the process of GSing a /5 would be greatly appreciated.
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  2. jdiaz

    jdiaz .

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    Get something with a five-speed tranny, because you aren't going to like a wide-ratio four-speed on the trail.

    Jon
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  3. Chopperman

    Chopperman I am dead

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    The front is easy. Just source a likely front and tale some measurements of the steering stem and go for one that is close. You can get bearings in a host of sizes. Even better is if you can remove the stem and machine a new one to suit the frame. Longer is not necessarily better as you have to see what your max range is on the rear.

    Which brings me to that: the rear can only swing so far and expect some sort of live from the u-joint. I believe this is the primary reason for the abbreviated life of the Airhead GS u-joints. If you want to get fancy, you can maybe see about adding a jackshaft and chain set up on the frame or somehow wedging a CV joint in there.

    The most problematic is the wheels. Go see how many DOT dual sport tires come in the size a /5 requires. not much. so you will probably want to lace a 17 on the back and a 21 on the front. tou will also ned to make sure the tire will fit in the swingarm. Especially when it goes flat.
    #3
  4. Frank Warner

    Frank Warner Traveller

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    Actually I think you will find the original /5 front has more travell than the original R80 G/S. The steering head is the same as the G/S and GS models IIRC.

    As far as rear wheel travel .. well the G/S has little trouble with the U joint, it is the GS paralevers that give trouble. So you maybe able to get some more here without redoing the drive shaft and/or joints.

    I'd have to look at the specks, but I think they came with a 180 watt alternator. 18 inch rear wheel and a 19 front, you should be able to get rear tyres ... the front may be more restricted. Things to look for would be the rear wheel spline between the wheel and the bevel drive - they ware.
    #4
  5. roberts

    roberts GS'er

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    This site might give you some ideas.
    http://www.wmb-moto.com/index.htm
    The links on the left side lead to photos and some
    technical information.

    Robert

    #5
  6. supercreep

    supercreep _______________

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    like this...

    Attached Files:

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  7. Stephen

    Stephen Long timer

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    Get a LWB /5 or better, a /6 with the stronger frame. /7's had further reinforced frames. You do not want to use the SWB swingarm. Trust me on this.

    The 750/6 was, IMO, one of the best Beemers ever made, really delivered on the "balanced performance" BS. The 750 engine is a sweet one. The later 800's are also very nice, but feel very different to me, not as punchy or highly tuned, but very smooth and revvy.

    18/19 tire choices are limited, but they do exist. Problem with the old BMWs is gonna be rear tire width, as Chop said. Cagiva Grand Canyon runs a 19 front, so there are some Pirellis out there, and some nasty old Conti's.
    #7
  8. storymitchell

    storymitchell Member of the proletariat

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    Hey - I saw this bike on EBay. Cheaper to buy than build? Does it look like the seller did it right?
    #8
  9. Stephen

    Stephen Long timer

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    I wouldn't touch that with somebody else's ten-foot pole.
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  10. storymitchell

    storymitchell Member of the proletariat

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    Why? What concerns you?
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  11. Stephen

    Stephen Long timer

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    Smartass answer: only the stuff I see, and the stuff I can't see. :D

    Possibly more helpful answer:
    Okay, it might be okay. But...well, let's start at the front...

    It may be an awesome dirt bike, but it sure has a street skin on the front. WTF?

    That front drum brake is good drum brake, but it's still a drum brake, a TLS at that. I'll explain if you ask.

    That fork has a stout brace, but /5 (and /6, and /7) forks need a lot more than that.

    So far, we're looking at a bike that needs a new front end.

    Tractor lights. Hmm. Do we know how good this guy is at wiring? I don't--he might be fantastic. Aren't tractors usually kinda heavy? I don't doubt that the lights are brighter than stock, though relays and an H4 worked wonders on these old bikes.

    Ninja subframe. Well. The stock is crap, for sure, but really...that saddle does nothing to get you in a good dirt riding posture.

    Enough. Look, it might be a great little scoot. MrToaster is certainly creative, and some of his solutions are cool--using the fork brace to get more clearance at the fender, for example. But all we've got here are two terrible photos of what looks like a pretty shabby bike. Rough can be good, sure; but not if it goes more than skin deep. We've just got an awful lot of known unknowns and unknown unknowns here. I might be more impressed if I got to look at it and ride it. As it is, it's just pixels and hype, so the default action is pass.
    #11