Author Topic: Harley Davidson - Gear Ratio change  (Read 2168 times)

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Offline Skipper

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Harley Davidson - Gear Ratio change
« on: March 23, 2015, 08:02:18 AM »
  8)  I've been on a little self impose sabbatical.  My last post was last year when I changed and scavenged oil in my new bike...the 2006 Heritage Softail.  Over the winter here in the USA in Iowa I finally got my furnace working in the garage.  I needed a new primary chain on the old 1998 FXSTC so I did a little research and decided to mess with the gear ratios at the same time.  Jerry Branch, of Branch Harley headwork fame, suggests that you change your final gear ratio from something like stock 2.92:1 to something like 3.50:1.  According to my calculations I could get there...3.48:1 by replacing the stock 25 tooth compensating sprocket on the motor to a 21 tooth.  Since I needed a new primary chain anyway...mine was stretched to the limit.....I bought an aftermarket sprocket and chain.....after being unable to obtain them from the motor company. 

About 4 hours later and a couple of skinned knuckles I got the new primary chain and 21 tooth compensating sprocket installed.  The first ride was somewhat ... what do I say???  difficult to adjust to.  The acceleration was way up...but so were the RPMs.  I do not have a tach, but I've been riding this bike since I bought it new in 1997.  If felt like 5 th gear was more like the old 4th gear....not quite, but close and the fastest I wanted to cruise was about 70 MPH.  Then it started getting cold and I have yet to have her out in 2015.  I can tell already that she's a lot quicker....its just going to be whether or not I can get used to the extra RPMs at cruising speed.  Out here in the backcountry of Iowa we like to go faster than the folks who are more urban.   I like high double digits and sometimes three digits when the mood strikes me.  Time will tell.  I've already looked in to upping the teeth on my transmission belt pulley from 32 to 34 teeth since the belt is stock and has about 90,000 miles on it anyway.  I'll see. 

Going from a 32 tooth transmission pulley to a 34 should change my final drive ratio from around 3.48:1 to something like 3.37:1 and should drop the RPMs a little bit at cruising speeds.  If I do I'll let you know.   Right now I'm going to have some fun drag racing some twin cam 96 and 103 stock bikes.  They will be scratching their heads when all they see is my rear.....have a great day.  Nice to be back. 
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Offline Richo

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Re: Harley Davidson - Gear Ratio change
« Reply #1 on: March 23, 2015, 03:03:16 PM »

THAT ... is so cool !!



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Offline LordDread

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Re: Harley Davidson - Gear Ratio change
« Reply #2 on: March 23, 2015, 03:22:34 PM »
Nice, i usually muck with the ratios when i get a bike, specially trail bikes, i will have max torque on the older ones thanks :P Dunno how it works with belts, prolly same as chains, but 1 tooth on the front is worth 3 on the rear is what i was told by an old mechanic.

My Fav has to be my old 2 stroke Dt175 full maxed the gears on that. Top speed was a woeful 100 kph (62 mph) but hey since that was the max speed limit anyways ..didnt use 1st gear off road, and on road it was get your weight as far forward as u can or you'd be looken at sky real fast :P

Offline Skipper

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Re: Harley Davidson - Gear Ratio change
« Reply #3 on: April 09, 2015, 11:48:40 AM »
 :-*  I turned 60 years old yesterday. Funny, when I blew by that twin cam 96 with big radius pipes and free flowing air cleaner after it was remapped I decided to leave the gear ratios on the ole 80 cu. in. 1998 FXSTC alone at 3.48-1, have some fun, and ya...60 isn't so bad when you finish first.... >:D 
Those who would trade their essential liberties for a little safety deserve neither safety nor liberty. (or something like that)