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1979 GS425 - Speed, fuel economy with touring fairing

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    #1

    1979 GS425 - Speed, fuel economy with touring fairing

    Hey all, I'm new to the forum, just bought a 1979 gs425 as my first bike. It came with a big Calafia touring fairing and saddlebags. I don't really like the look much and will probably get a smaller sport fairing in the future, but for now it is staying.

    Anyway, I rode the bike from Calgary, Ab to Medicine hat, Ab last weekend (about 300km) and was rather disappointed with the bikes performance. It would barely get up to 120km/h on flat ground and had problems climbing hills and with any sort of headwind gusts. It also got pretty dismal fuel economy at just over 6L/100km (about 40mpg). Is this the fault of the big fairing, or is the bike severly out of tune? I checked the ignition points yesterday and set the timing, but it wasn't far off and that didn't help much. I plan to take the carburetors apart and clean them out when I have some time.

    What are reasonable performance figures to expect from this bike, and what would cause lack of midrange/top end power and crappy fuel economy?

    Thanks, Jacob
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    #2
    when you run any machine for all it is worth the economy goes way down. i have a 200cc honda that gives me 80mpg whern i drive it at a tad under 50mph. When i am doing 60 or a little more in faster traffic riding the mileage goes down to a hair over 60 mpg. That is a small engine. enjoy it and dont destroy it.

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      #3
      GS 425 E 1979
      Overall Length: 2 090 mm (82.3 in)
      Overall Width: 835 mm (32.9 in)
      Overall Height: 1 100 mm (43.3 in)
      Seat Height: 785 mm (30.9 in)
      Wheelbase: 1 385 mm (54.5 in)
      Ground Clearance: 155 mm (6.1 in)
      Dry Weight: 170 kg (374 lbs)
      Engine type: Air-cooled 423 cc inline-2, DOHC, 4 valves. 40 hp (29,5 kW)/ 8,500 rpm, 31,3 Nm/ 7,000 rpm. 6-speed gearbox.

      Having 40 hp, I would guess pushing a big fairing would make a large difference in fuel economy, top speed and acceleration. I had a 450E along about 1983 and it got about 45-48 miles to a gallon and topped out at 90 mph. 90 mph would be aprox 144kph. It was a bare bike, no fairing at all.

      Earl
      Komorebi-The light filtering through the trees.

      I would rather sit on a pumpkin and have it all to myself than be crowded on a velvet cushion. H.D.T.

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        #4
        Thanks for the replies. I guess I'll try taking the fairing off and see how much it improves. Though I would think it would be able to do a little better than 120km/h at WOT.

        Can anyone tell me what a good source is for a cheap set of sidemount headlight brackets and headlight bucket? I also need front signal lights. The headlight and signals are integrated into the fairing currently.

        The reason for my concern was reviews I had read online from other owners of the same bike who said they got 4L/100km (about 60mpg - that's imperial gallons not US) and top speed of about 100mph (160km/h).

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          #5
          No power...

          Something is definitely not on with the way this engine is tuned. I didn't get a chance to take the carb apart and clean it yet, and that is definitely going to happen on the weekend, but when I rode to work this morning, it would barely get up to 110km/h. There was a bit of a head wind, but even in the wake of a large truck, it barely got up to 120. And that was in 5th. It wouldn't maintain it in 6th gear.

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