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Thread: 76 R90/6 - ideal RPM's & engine braking

  1. #16
    Registered User VIEJO's Avatar
    Join Date
    Feb 2013
    Location
    Hutto, Texas
    Posts
    48
    Quote Originally Posted by VIEJO View Post
    Welcome!

    My first BMW was a '76 R90/6.... I bought it new, put about 200K on it and regret ever parting with it. In retrospect it was probably the best bike I've ever owned.

    As noted in one of the responses below the '76 has several good features not found on the earlier /6's. One of these features (also on the '75 /6's I believe) is that the cylinders have an extra longitudinal boss in the cooling fins which enables the cylinder to accept a bore out to 1000cc. I did this to my bike at about 60K to take out the slight high end buzz that most of the 900cc bikes experienced. I had the new pistons teflon coated before installing and never had any trouble with the conversion. I stayed with the stock Bing carb's but added a set of slightly less restrictive megaphones from D&D in Haltom City, TX., which was like putting a slightly higher duration cam in..... greatly increased the throttle response. The only other thing I would consider would be a /7 front end to get the twin disc brake setup.

    Congratulations.... you've got one of the best!
    A couple of additions to the above......

    I second the motion that you link up with the Airheads Beemer Club ASAP.... incredible resource for information/guidance/folly on all things Airhead related. In all probability every question you may have about Airheads has been answered there.

    With regards to your question(s) about shifting in general. Airheads are characterized by a rather clunky shifting feel.... nothing amiss, just the result of fairly heavy flywheels (I do not subscribe to the "lighten the flywheels" school of thought). Most Airhead riders I know will "pre-load" the shifter slightly just prior to shifting, up or down. Not a great deal of pressure, only enough to take the slack out of the shifter. If you decide to do this it will become second nature quickly..... I do it on my K bike also.

    There is a plethora of aftermarket gear available to bring your Airhead into the 21st Century and most of it is quite good. However, your low milage '76 is quite capable of running for many miles/years with the gear originally fitted. Don't be in a headlong rush to start "modernizing" unless you have deep pockets and the money's burning a hole in them. If the R90 series had a weak spot it was the ignition/charging system; good for the time but still room for improvement. Consider a modern solid state ignition/charging system for an initial upgrade. EME [www.euromotoelectrics.com] is a great resource for all things electric.

  2. #17
    Airhead
    Join Date
    Aug 2010
    Location
    Scottsdale, AZ
    Posts
    97

    4K and blip it on downshifts

    On my stock 1975/6 4K is the sweet spot.

    On 1->2 shifts I preload the shifter to avoid the massive 'clunk'. I get it right 7 times out of ten, all occasions for rejoicing. The other 3 times I check the rear view mirrors to see if my gearbox has shed parts. After almost 30 years with the bike this is the best I can manage, having long resigned myself to the belief that the clunk is a feature, not a problem.

    And on all downshifts I rev match by blipping the throttle when the clutch is disengaged. This makes for smooth shifts. Otherwise the heavy stock flywheel slows things down too much and you are looking at earlier clutch plate replacement.

    Enjoy your bike - itís a beauty.

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