This is the sixth in a series of reports intended to document the results of progressive modifications to the LS650 engine.

Part 1 outlined the project, set the rules, and established the baseline performance values for a box-stock LS650.  You can find Part 1 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1620523526

Part 2 examined the airbox.  We improved performance dramatically with a few simple and inexpensive modifications.  It was a lot of bang for the bucks.  You can find Part 2 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1621150483

Part 3 took a hard look at the exhaust system.   We tried a Dyna muffler and a hybrid muffler (home-built).  We also tried the larger Mac header pipe.  The exhaust modifications provided significant improvements in acceleration and fuel economy.   You can find Part 3 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1623048749

Part 4 installed a performance carburetor and revisited the air filter.  You can find Part 4 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1625732492

Part 5 installed a new camshaft with higher lift and duration.  The results were gratifying and informative.  With some valve overlap, the exhaust header took on a new role.  You can find Part 5 here.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1626391255

Part 6 installs a lighter flywheel.   Reducing the weight of the rotating assembly should consume less horsepower, leaving more power to drive the motorcycle.  We’re looking for quicker acceleration.  It will also reduce the weight of the motorcycle which will provide a modest improvement in the horsepower to weight ratio.

What I am about to describe worked good for me.  If you decide to try this stuff on your own, you assume responsibility for the outcome.  If you don’t have the skills, don’t do it.  If you don’t understand something, STOP and get help.  Get a manual.  Read up.  Comply with ALL the safety requirements outlined in the manual.  Make sure you know what you are doing before attempting any of these modifications.

Let’s get started.

I know from experience that installing a three-inch flywheel does not seem to adversely affect operation.  The engine runs fine with the smaller flywheel.  Seat-o-da-pants it feels like it’s a bit faster.  Now it’s time to measure performance and compare.  Will the lighter flywheel improve acceleration?  What effect will it have on top speed?

The 3” flywheel only weighs 15 ounces.  If nothing else, it reduces the curb weight by 5 pounds.  It should also improve acceleration.   Less rotating mass should spin up faster.

To get your hands on one of these, you need a lathe, or you must pay someone to machine off the excess material.  Take the O.D. down to 3.000”, maintain concentricity within .001” TIR.  Here you see the difference between the 6.5” flywheel and the 3” flywheel.

You can find the puller on Amazon or eBay.  It costs about $50 bucks.  BikeMaster 152481

A 36mm wrench comes in handy for holding the alternator rotor when you remove or torque the rotor bolt.  There are ways around this wrench, but life is much easier when you have one of these.

The flywheel resides behind the alternator rotor.  To remove the alternator cover you must remove the drive pulley cover.  There’s only three bolts that hold the pulley cover on the engine.

The left side footrest assembly must be moved out of the way.  Since the side-stand switch is attached you need to free up the wires to the switch.  If you don’t free up the wires, you may damage the switch when you try to move the footrest.  Remove any zip ties that restrain the wires running along the left side frame rail.

Loosen the small bolt and swing the clip out of the way.

There’s not much to it.  Just a few chunks of scrap lumber.  It’s versatile.  Allows working on the bike without fear of dumping the whole shitteree on it’s side.