Did Harley make their Starters stronger as engine size increased?
I had always wondered if Harley increased the strength of their Starters as engine size increased. This is what I found out.
(This study only deals with Softails from 1994-2010. My Softail parts books do not go beyond 2010).
Looking at the Starter itself, through the years as engines increased from 80" to 88" to 96" Harley stayed with the same stock 1.2kw starter. I based this on HD Armature part number 31515-90. From 1990-2010 Harley used the same exact Armature. I can only assume the Field Coils are the same also; Harley does not list replacement parts for their Field Coils so I can not compare them through the parts books but I'm assuming the Field Coils did NOT changed because to buy a new Starter the part number is still the same as it was in 1994. So as I move forward with this study I'm assuming the starter remained a 1.2kw Starter from 1990-2010.
There was a Starter mounting change in 2007. In 2007 the Starter-to-Transmission mounting plate was eliminated and the Starter was redesigned to bolt directly onto the Inner Primary. I believe this to be a good design because now this new Starter had a Starter Shaft Support that's actually part of the Starter Body and it protrudes inside of the Inner Primary. By doing this it eliminated the need to remove the Outer Primary Cover when removing and installing a Starter. The Starter now looks and installs much like a car starter. However it's a tight fit, the only way to get access to this Starter is by removing the Oil Tank or going in through the back by removing the Rear Tire.
Ok so we know that the Harley "Softail" Starter is the same strength from 1990 through 2010 (1.2kw). And we know that in 2007 the Starter got a different design so it could have better shaft support and could be mounted directly to the Inner Primary. So is that it..., is this Starter doing more work now because it's starting 88" and 96" engines then it was when it was originally designed for the 80" engine? Well the answer is yes and no. To understand this we must look at another deciding factor.
Beginning in 1994 the Starter Gear had 10 teeth and the Starter Ring Gear had 102 teeth. This did not change until 2007. So from 1994 -2006 the Starter Gear Ratio remained the same so the answer is Yes... the Starter had to work harder with the introduction of the 88" Engines. In 2007 the Starter Ring Gear changed from 102 teeth to 106 teeth while the Starter Gear remained unchanged at 10 teeth. By the addition of 4 teeth on the Starter Ring Gear this changed the gear ratio slightly to give the Starter more leverage and the ability to do more work. I had wondered how Harley designed the Starter Ring Gear to get more teeth. Did they thin the teeth a little so they could crowd in 4 more teeth on the Starter Ring Gear or did they keep the teeth the same thickness and increase the diameter of the Starter Ring Gear so they could fit 4 more teeth on the ring? So I measured the diameter of a 102 tooth Starter Ring Gear that was lying around and then I went online to see what the diameter of the 2007-2010 Starter Ring Gear was. What I found was that the Starter Ring Gear diameter increased by 5/16" (102 tooth measured 8-10/16" and the 106 tooth measured 8-15/16"). So by increasing the diameter of the Starter Ring Gear they again increased leverage and increased the ability of the Starter to do even more work. Remember this change happened in 2007 which was also when the 96" Engine came out standard on all Softails. So with the addition of more teeth on the Starter Ring Gear and the increased diameter of the Starter Ring Gear I doubt the Starter is working any harder then it was with the 88" Engine.
I'm also thinking now that a 2nd reason for the Starter mounting change in 2007 was so the Starter could easily be relocated to a new position which is necessary due to the Starter Ring Gear's larger diameter. (Useless side note: with the addition of added leveraged to the Starter Ring Gear there's will be a decrease to the speed at which the Engine turns over when the Starter in engaged. I've rode 2007 and later Softails and it's not noticeable).
So there it is... I have always wondered if the strength of the Softail Starter changed through the years as Engine sized increased. From 1990-2010 on Softail models it looks like the Starter stayed at 1.2kw. I did discover that the Starter Gear Ratio changed in 2007 to help in the starting of the 96" Engine.