16-Tooth Front Sprocket

WHY?   Higher gearing.  While I've had very few complaints with this incredible machine I've often wished that it had a 7th gear for highway cruising.  Don't get me wrong--I believe that Suzuki has done a great job of picking the best gearing for all-around riding; most of my riding is backroads touring, however, and I wanted to experiment with a little taller gearing. In stock trim my DL650 turns about 5600 RPM at an honest 70 MPH (Forget the stock speedometer--it reads too low; to correct it, see this handy gadget).  While that's no strain on an engine that loves to rev and redlines at 10,500 RPM it is a little busier than I like. 

The 15-tooth front sprocket and 47-tooth rear sprocket combine to yield a 3.13:1 gear ratio; changing the front sprocket to a 16-tooth unit would yield a gear ratio of 2.94:1 which I hoped would produce a little more relaxed touring speed without completely destroying the bike's acceleration.  I've had good luck with the good folks at Adventure Motostuff, so I checked their site and found a listing for the sprocket I wanted.  I've had excellent service from JT sprockets on bikes in the past, so I selected a JT steel sprocket for a 525 chain--just $12.56 plus shipping.

SERVICE. Pretty good Two days after placing the order I received a confirmation email saying that the order had shipped, and it arrived via USPS Priority mail two days later. 

INSTALLATION. Not a terribly difficult job, and one that can be done by the average home mechanic; the entire process took me about an hour.  As with most mechanic work, having the proper tools can make the much easier; besides the usual set of metric tools you'll need to have a 32mm socket (1-1/4" will also work) and an impact wrench is a plus.  Here are the steps you'll need to take:

1.  Remove the three small bolts holding on the front sprocket cover; you'll need an 8mm socket:

2.  You'll need to move the clutch screw assembly so that you can get to the sprocket nut.  Use a 10mm socket to remove the two bolts holding it in place and move the assembly aside; look at it closely so that you can re-assemble it when the pieces come apart. 

3.  Now you're ready to tackle the toughest part--getting the sprocket nut loose.  It is tightened down snugly and held in place with thread locking compound.  I used a 32mm socket on my air impact wrench; to keep the sprocket from turning I stood on the rear brake pedal and reached over the seat to work the impact wrench.  The nut zipped right off with no problem.  If you don't have access to an impact wrench you'll need to brace the rear tire so that it won't turn when you tug on it with a ratchet; a steel bar or pipe between the spokes will do the trick:

4.  Remove the sprocket nut and washer and you're ready to remove the sprocket.  You'll need to get some slack in the chain so you'll need to loosen the rear axle nut.  Pull the cotter pin from the nut and loosen it--it'll be pretty tight.

5.  Use a 5mm hex wrench to loosen the two chain adjusters to gain some slack in the chain:

6.  With some slack in the chain you'll be able to grasp the stock sprocket with your fingers and pull it off.  Separate the sprocket from the chain and slide the new sprocket into place in the chain; with the chain wrapped around it, slide the new sprocket onto the shaft.  Place the washer in place, use some blue LocTite on the sprocket nut and tighten it to 105 Ft/lbs. torque.  One edge of the washer can now be bent down onto the nut to keep it in place; that move is accomplished pretty easily with a pair of slip-joint pliers.

7.  Tighten the chain adjusters on each side of the wheel so that the slack in the chain in between 0.8"-1.2" at the midpoint; this adjustment should be made while the bike is on the sidestand.  Be sure that the adjusters are aligned on the same marks on each side of the swingarm.  Here's an easy way to check the chain:

8.  Tighten the axle nut to 73 ft/lbs. and re-insert the cotter pin.  Replace the clutch screw assembly and the sprocket cover.  Ride.

RESULTS.  Nice.  There is no such thing as a free lunch with a gear change; if you gain on the top end physics dictates that you'll lose it on the bottom.  The butt-dyno will confirm that a small amount of acceleration was lost with this swap, but it was certainly in the acceptable range for me.  I waited with anticipation as I ran through the gears, and I was pleasantly surprised to see the tach settle in at 5100 RPM at an honest 70 MPH--about 500 RPM lower than with the stock gearing.  The engine also sounded much more relaxed at cruising speed.  Since the speedometer signal pickup on the DL650 is on the front wheel it is not affected by this change.

Plus:  Less noise at cruising speed, better fuel economy (3-4 MPG currently)

Minus:  Slightly less acceleration in any gear

Others who have done this swap have noted that there is some increased gear noise and vibration as the original sprocket has rubber damper while the replacement does not.  This has not been my experience; I sense no additional vibration, and I have noticed no additional noise--probably because I wear a helmet that is pretty well soundproofed. If you want the rubber damper and don't mind spending more, I'm told that the GSXR600 front sprocket (#27510-20A10) is a 16T unit that will fit.

WORTH THE MONEY? Depends.  This was a heckuva deal for me, as I've tuned my bike perfectly to my riding style and spent only about $15 and an hour's time to do it.  I'm happy as can be, but this might not be your cup o' tea if you have a different riding style.  If you want the extra acceleration or do some off-road riding and need some lower gearing you might want to forget this one.