Dyna gets the 30T pulley mod

Changing out sprockets/counter sprockets on a regular chain driven bike is a fairly common practice, considered a cheap and easy way to change the gearing on a stock bike – taller for better freeway riding, shorter for city duty.

The Dyna, with its 6 speed transmission, is geared tall from the factory. In its stock setup, 6th gear is only really used at 80 mph and up (any earlier and it
starts to lug) – not very realistic when you consider the national legal limit is 75 mph.

I decided, since I primarily use the bike for around town (it has no fairing or windshield), that I wanted to lower the gearing.

Considering the Dyna’s drive configuration, there are several options to lower the stock  gearing (larger rear sprocket, smaller transmission sprocket, smaller engine sprocket), and of course, with each option you’ll need to weigh up any ‘negatives’ e.g. associated cost, effort (mechanical ability), specialty tools required, speed sensor impact, belt length, etc.). I decided to go with the smaller transmission gear (from 32T to 30T). The only real negative – speedo would be out by about 5-7 mph (speed sensor is driven by the transmission sprocket). I hear there is some electronic speed sensor calibration available, but at this point, I’m not too worried.

With the transmission sprocket buried in the primary/transmission case, this was going to be a bit more work than doing a gear change on a standard chain-driven bike.

Stock configuration runs a 32T txmn pulley, 66t rear sprocket and a 131t belt. Changing to a 30t txmn gear means we get to use the stock length belt. Parts list for this upgrade included:

• Andrews 30t transmission pulley (drag# 1201-0227)
• Primary gasket kit
• 5 new chaincase fasteners (recommended in service manual)
• Heavy-Duty clutch spring (optional)

“Special” tools list include:

I had been dragging my feet with the mod, between the honey-do list and wanting to ride in any spare time, the parts and tools lay on my work bench for weeks. I ended up taking the bike to Miles and Brian of DIA Motorsports to do the work. They have a great set up, clean shop, fast turn-around and they won’t charge you an arm and a leg.

FXDF Fat Bob

First thing I noticed was the clutch pull – it grabs earlier and more precisely.  Then it  was time for a test ride. Whoa! It pulls great. No more stumbling, lag, sluggish feeling. It’s smooth and fast. Also, looks like I can start using OD.

I did notice the speedo seems to be out quite a bit. I’ll run it with the GPS over the weekend to measure the difference. Maybe I’ll need to consider recalibrating the speedometer sooner rather than later.

If you’re considering this mod, I  highly recommend it – great bang for the buck upgrade.  I’m very happy with the outcome.

Here’s to hoping the weather holds out this weekend…

Tags: Dragging My Feet, Drive Configuration, Electronic Speed, Gasket Kit, Heavy Duty Clutch, Impact Wrench, Mechanical Ability, Rear Sprocket, Sensor Calibration, Special Tools, Specialty Tools, Speed Sensor, Speed Transmission, Speedo, Stock Bike, Stock Configuration, Stock Length, Stock Setup, Transmission Case, Transmission Gear, Transmission Pulley