Installation of 15-Tooth Front Sprocket


The Factory gearing is very tall. Highway speeds in the high gears produce very low engine speeds. Perhaps too low for brisk acceleration for passing or emergencies without downshifting. Also, it really isn't necessary to be able to go 75 mph in 1st gear. Installation of a smaller 15-tooth versus the stock 16-tooth front sprocket provides a modest increase in the final drive gear ratio from 4.348 to 4.638. This has the effect of slightly increasing the engine rpm at all speeds in all gears.

primary reduction ratio = 68 / 43 = 1.581 (internal transmission gears)

secondary reduction ratio = 44 / 16 = 2.750 (44 = teeth on rear sprocket, 16 = teeth on front sprocket)

Stock final drive ratio = primary reduction ratio x secondary reduction ratio = 1.581 x 2.750 = 4.348

Modified final drive ratio = 1.581 x (44 / 15) = 1.581 x 2.933 = 4.638 (15 = teeth on smaller front sprocket)

Approximate Engine RPM in Gears (Stock / 15-Tooth Sprocket)
Speed (mph) 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
203000 / 32002200 / 24001800 / 19001600 / 1700------ / 1500------
304500 / 48003300 / 36002700 / 29002400 / 26002200 / 23002000 / 2200
406000 / 64004400 / 47003600 / 39003200 / 34002900 / 31002700 / 2900
507500 / 80005500 / 59004500 / 48004000 / 43003600 / 38003400 / 3600
609000 / 96006600 / 71005400 / 58004800 / 51004300 / 46004000 / 4300
7010500 / 112007700 / 82006300 / 67005600 / 60005000 / 54004700 / 5000
80------8800 / 94007200 / 76006400 / 68005700 / 61005300 / 5700
90------9900 / 105008000 / 86007200 / 76006400 / 69006000 / 6400
100------11000 / ------8900 / 95007900 / 85007100 / 76006600 / 7100

At all road speeds, the engine operates at higher rpm's where more power is available for better acceleration. Also, because of the torque multiplication effects of transmission gearing, the modified gear ratio has the effect of increasing the effective rear wheel torque by a computable amount:

Rear Wheel Torque with Smaller Front Sprocket = Rear Wheel Torque with Stock Sprocket x (16 / 15), or, a 6.67% increase.

Note that this does not theoretically increase the power at the rear wheel. At each engine rpm the shorter gearing increases multiplied torque at the wheel but also decreases the wheel rpm in the exact proportion to maintain the identical power value. This is also not a reference to the 'Rear Wheel Torque Curve' which is a measure of the engine's ability to deliver torque to the rear wheel independent of the torque multiplication effects of the transmission.

The smaller sprocket is, however, lighter in weight and thus has less rotational mass to accelerate. The reduced transmission power losses due to this factor are probably very small.

Fuel economy will be reduced by about 5-6%

A Theoretical Performance Comparison Table is Shown Here.

The smaller sprocket costs about $35 and is available from Sprocket Specialists, Part #556-15 for the 530 chain.

Due to the way that the speed sensor is used to compute road speed, by measuring the countershaft rotational velocity and using the known stock secondary reduction ratio and rear wheel size to convert that to miles per hour, a speedometer error reading high by 6-7% will be introduced. This is in addition to any existing stock speedometer error.

Another option would be to install a larger (more teeth) rear sprocket. You would have to go up three teeth on the rear (from 44 to 47) to match the one tooth decrease on the front to achieve the same final drive ratio increase. Rear sprockets are a bit more expensive at about $60. Also, the stock chain is too short for the 47 tooth rear sprocket and this option would require a longer chain. Of course, nothing says that you can't change both the front and rear sprockets to achieve the characteristics you want.

Another consideration is that installation of a smaller front sprocket will necessitate a small increase in the bike's wheelbase to maintain proper chain tension (in my case by about 5 mm). This will reduce the tendency of the bike to wheelie under acceleration although this is overwhelmed by the increased acceleration potential. A larger rear sprocket will reduce the wheelbase and increase the wheelie potential even more.

A smaller front sprocket may also increase wear on the plastic chain guide on top of the swingarm due to the decreased clearance between the chain and the guide.

Lastly, there is some thought that the smaller front sprocket will increase chain wear due to the chain bending more sharply to traverse the sprocket teeth of reduced radius. A larger rear sprocket will decrease chain wear for the opposite reason. These effects, however, have never actually been quantified.


Place bike on Centerstand

Remove Left Side Footpeg

  • Remove Shift Linkage Ball Joint Bolt
  • Remove Footpeg Plate Bolts
  • Pull Shift Linkage Rod Through Frame and Remove Footpeg Assembly

1600 x 1200 1600 x 1200 1600 x 1200
1600 x 1200 1600 x 1200

Remove Drive Sprocket Cover

1600 x 1200 1600 x 1200 1600 x 1200 1600 x 1200

Loosen Drive Sprocket Nut

  • Remove Drive Chain Guide
  • Bend Up Sprocket Nut Lock Nut Flange
  • Place Transmission in 1st Gear by Pushing Forward (Clockwise) on Linkage Stub with Clutch Pulled in
  • Jam or Block Rear Wheel to Prevent Rotation in Forward Direction.
  • Loosen Sprocket Nut with 36mm Socket Head

1600 x 1200 1600 x 1200 1600 x 1200 1600 x 1200

Loosen Rear Axle

  • Loosen Brake Caliper Bracket Bolt
  • Verify Rear Wheel Still Blocked To Prevent Rotation in Forward Direction
  • Loosen Rear Axle Nut
  • Loosen Chain Adjusting Bolt Lock Nuts
  • Tighten Chain Slack Adjusting Bolts to Free Rear Axle
  • Push Wheel Forward To Increase Slack On Chain

1600 x 1200 1600 x 1200 1600 x 1200 1600 x 1200

Remove Stock Front Drive Sprocket

  • Unscrew Sprocket Nut the Rest of the Way Out
  • Pull Off Lock Nut
  • Pull Sprocket from Spindle and Unfasten Chain
1600 x 1200 1600 x 1200 1600 x 1200

Install New Sprocket

  • Place New Sprocket on Chain and Slip onto Spindle
  • Insert Lock Nut on Spindle
  • Jam Rear Wheel To Prevent Rotation in Backward Direction
  • Insert and Tighten Sprocket Nut (85Nm, 61 lb-ft)
  • Pry and Hammer Down Lock Nut Flange on Flat Area of Lock Nut
  • Reinstall Drive Chain Guide (Not Too Functional Now Though)
  • Reinstall Drive Sprocket Cover
  • Reinstall Left Footpeg, tighten Bracket Screws to 30Nm, 22 lb-ft
  • Reconnect Shift Linkage Rod on Transmission with Ball Joint Bolt

1600 x 1200

Next, remove any wheel blocking device and adjust the drive chain slack. A page describing that procedure is here.

Check Your Work

  • Take Bike for a Careful Test Ride
  • Recheck All Bolts Properly Tightened
  • Take Bike for a Performance Test Ride

Subjective Riding Impressions:

  • Bike is Quicker, Noticeably but Not Dramatically
    • 1st Gear Especially, 2nd Also
    • Familiar Throttle Openings Produce More Acceleration
    • Need to be Careful with Front End Lightness in 1st & 2nd Gears with Large Throttle Openings
  • Increased rpm Does Not Seem to Cause Increased Felt Vibes at Familiar Speeds
  • Low Speed Launches Feel Crisper, Less Clutch Slippage
  • More Responsive at Highway Speeds

I replaced the stock plastic sprocket cover with a silver anodized Billet Aluminum cover designed and manufactured by Frank Mill (RoadDog). It is also available in unfinished aluminum for polishing or anodized black. Please visit or email Mike Pijanka for price and availability. Mike is also a representative for excellent Rizoma accessories.

The stock cover can be removed by:

  • First disconnect the shift shaft at the upper side (see picture far above). No need to remove it entirely. With the shaft disconnected the shifter can be moved (rotated, pull in clutch lever) for access to the top left bolt of the cover.
  • Remove the four cover screws (5mm Allen wrench) as shown in picture far above.
  • Work the cover off around the shift shaft.
  • Remove the top bolt from the chain guide.

Install the cover by inserting the top bracket in place then insert the sprocket cover and attach to the bike with the three bolts. The longest (85 mm) bolt gets the tube spacer and screws into the bottom right empty screw hole. The bottom left screw hole is left empty. The shortest (35 mm) bolt fits through the cover, through the bracket, then into the top screw hole for the chain guide. The middle length (50 mm) goes into the top right cover screw hole. The top left cover screw hole is left empty. All the hoses route in front of the sprocket cover.

1600 x 1200 1600 x 1200

Installed pictures:

1600 x 1200 1600 x 1200

Back to Main Page

Last Updated: 01-22-2004

Copyright © 2001-03, Patrick Glenn, All Rights Reserved.
Yamaha® and FZ1® are registered trademarks of the Yamaha Motor Corporation.
This site is not affiliated in any way with the Yamaha Motor Corporation.

The information presented here reflects solely my personal experience with my motorcycle and is presented for entertainment purposes only. No information presented here is to be relied upon for issues of rider safety nor to replace the services of a qualified service technician. Any attempts to follow or duplicate any of these procedures are done so completely at your own risk. By reading the information on this site, you agree to assume complete responsibility for any and all actual or consequential damages that may arise from any information presented herein.