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78HP sub 300 pound Supermono Hawk transplant anyone?

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  • 78HP sub 300 pound Supermono Hawk transplant anyone?

    I've been looking at adapting a KTM 690 Duke headlight for my Hawk so I've been poking around in all things KTM lately. Love their RC8 but curiously they look to be developing a smaller sportbike with the 690 LC4 thumper engine. So far it's looking like a sub 300 pound 78 horsepower sportbike. Can you say that's would be a dream Hawk? Looking more into the engine it's a variation of the same single cylinder of their other 690 models. The 690 duke claims 65 horsepower bone stock. Probably not RWHP. Either way it's claimed they're sqeezing out 78 for the sportbike prototype. How much more can we get from a modern thumper engine?
    So anyway why am I going on so about the KTM? Well I found some images of the engine and they made me go Hmmmm... Downloaded the 690 Duke parts manual that shows exploded views of the engine and frame. I then got out my Hawk manual and just did some eyeball correlation on fitting a Hawk with this LC4 motor.

    Drive sprocket? It's on the correct side. Who knows how it would line up but I've heard of other engine/bike swaps where that shaft and sprocket were lined up and spaced so the transplant worked.

    Engine mounts? It is mounted in a similar fashion as the hawk. The rear engine mount of the LC4 motor looks horizontally rearward of the drive shaft. The Hawk's looks like it is located in the same neighborhood but a bit higher. Could some sort of strong adapter bracketry mate the two? The front mount is very similar to where the Hawk engine mounts. The exact dimensions of the LC4 motor and where that mount would fall after everything else was lined up may also need to be solved with some modification of the front Hawk frame mount or again some adapter technology. Just eyeballing the thing in pics though doesn't make me think it's equivalent to sending a man to Mars.

    Engine dimensions? Well it sure as hell looks almost like a modern version of a Hawk engine minus the front cylinder head. It may be narrow enough to work in the Hawk frame. The KTM 690 bikes are known to be rather slim. Of course if this all could work you would have a strange open gap where that front head used to be. Everyone's always been looking for an alternate place to place the battery & electronics. Maybe up front there?

    Weight? I don't know what the Hawk motor weighs vs the KTM but it might be a fair bet the KTM motor is lighter since it's only sporting one tower of aluminum. The proposed RC4 sportbike is supposed to weigh just under 300 pounds stock with this motor. We got some Hawks around here on serious diets that are just a few cheeseburgers over 300. Maybe a lighter motor will drop them sub 300?

    Just pipe dreaming here but for all those racers sidelined by the SV and street Hawk's that have Ducati amounts of money into them and all of us who just plain love these little bikes but wish they had modern power. Maybe?
    Last edited by pdubhawk; 11-25-2008, 11:50 PM.
    "I am not a demon. I am a lizard, a shark, a heat-seeking panther. I want to be Bob Denver on acid playing the accordion."

  • #2
    As a track bike engine it wouldn't be a bad start, although if you really want to get into this sort of thing then take a look at the world of supermonos: Single cylinder bikes with power to weight ratios that almost compare to GP bikes! I think the closest to the supermono series that you guys get in the US is moto 450, which looks like fun too.
    As for as a road bike engine, the LC4 is pretty average to be honest. I've a friend who's big into supermotos, he's had loads of the things, and in terms of reliability the LC4 is fairly mediocre (90mph top speed, and if you hold it north of 80 for very long you'll get to see what a con rod looks like), plus more or less all modern singles need oil changes at alarming regularity. Personally, if KTM tuned an LC4 much harder than it is already, I wouldn't touch it with yours...
    In the garage at the moment:

    '83 Katana 1100
    '89 Bros 680
    '96 ZX7R

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    • #3
      The weight of a Hawk motor is 134lbs according to the manual.
      -I'm sorry....I did not know she was your sister.
      -If Buckleys cold mixture went rancid......how would anybody know????
      -Dont piss off the quiet guy with the chain saw.

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      • #4
        I wonder if this will have the same problem as the new 680cc transalp engine which is the closed loop feedback system for emissions. Is there an O2 sensor aft of the catalytic converter sending feedback data to the engine controller?

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