Sunday, March 20, 2011

something new

Another bit of news on the supermono front -- a new engine!!!  Kits to bump the drz to the north end of 50 hp will run me about 500 bucks.  Beyond that is a stroker motor, split the case, etc etc, and then we're looking at at least 800 bones.  Imagine my surprise when I stole this for $359, including wiring harness and digital tach:
Its a 2006 husqvarna 610sm engine.  50hp in base form, with 6 speeds.  No dry sump.  Requires a 41mm carb, but it looks like the rear mount and swingarm pivot is the 17mm I've been working with.  Radiator might be a bit of a question mark, but anything's possible.  Even saw a video of it running before the owner parted it out.  The question is, what do I do with it?  The way I see it I have a few options...

1.  Put it in the current tigcraft frame.  I think it would go with not too much work, but I still feel the wheelbase of that bike is a tad on the long side for a supermono.  Would be the cheapest option, and while I'm fitting this engine, I could install the new tank, fit a different exhaust, swingarm, bodywork, etc, etc.  Could have it running far sooner as well.
2.  Use a 125 frame as a starting point.  Someone has done this already.  This is an example of the same engine installed in a cagiva mito frame.  Non-existent in North America, but relatively plentiful in the UK.  Several for sale on eBay all the time, just need to get it over here for me to use it.  By these pics, it seems like the engine was meant for the frame!
Not sure what radiator is being used here.  With just a bare frame, I can fit the mito tank I already have, incorporate the sturdier (but heavier) rg125 swingarm I've got waiting, use the rs125 wheels and forks from the current mono, as well as the bodywork.  A more straightforward build.
I would make my own rear subframe in order to use the rs125 rear seat I have waiting for me in Fort Frances.  The mito chassis is used by many supermono racers in the UK -- ktm and even jawa engines can be made to work with little effort.  Haven't hefted one myself, but while it is alloy, the front headstock and rear swingarm areas are all cast, and appear to be quite heavy.  I also wonder about the vibration and the aluminum chassis... cracking?

3.  The next option is the clean sheet approach.  While this is more effort, considering I have all the ancilliaries in place already (swingarm, wheels, engine, rear subframe, tank, etc), it might be the way to go.  I've got quite a bit of 4130 left over, in the garage.  The end result will be lighter, and I have plenty of inspiration to go by.
 I even have an rs125 to orient a jig around (thanks Stephen!).  I've started a jig just for fun in the garage, and will see how square I can get things set up.  Aside from an old lathe bed that dad dropped off years ago, there isn't a flat surface in he entire garage.  With that in mind I'm using it as a basis to create a simple two-channel jig.  I'll use the rs125 frame as a starting point and see what kind of geometry I come up with.  I think that frame is a bit too small for this engine, but extending the main frame by perhaps 1" should do the trick.  With that in mind, I'll see what kind of response I get from people on eBay...

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