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Iron-Butt Hardcore
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Discussion Starter #1 (Edited)
Greetings,

So having been planning it for a while, the planets finally aligned in such a way as to actually allow me to perform the primary gear change I hear everyone raving about--commonly referred to as "3.37 gearing."

At any rate, last night I removed the stock 25-tooth compensating sprocket and 36-tooth clutch basket, and installed 24-tooth and 37-tooth replacements. The result? The primary gear reduction has been changed from 1.44:1 to 1.54:1 (3.37:1 final drive ratio as compared to 3.15:1, stock).

Wow. The perfomance of the bike has really changed. I don't notice any objectionable RPM increase--not even on the highway--but the torque multiplication from the increased mechanical advantage is VERY noticeable. Acceleration is "hell yeah!" fast, and the bike feels more like it effortlessly responds to right-hand input than before. Indeed, this feels like it is the "correct" gearing for the bike--whereas the stock gearing felt a little tall.

The debate over whether an overdrive 6-speed is called for will doubtlessly continue. But it is not "needed" as a result of the primary gearing swap, IMHO.

Thanks to Doc, MegaGlide and others for their advice. This is a kick-ass mod.

-Fat
 

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Premium Member
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1,389 Posts
..Your experience is what I've heard from just about every one whos made the change. Glad you like it!!
I can just never figure out why one would bump compression, put on free flowing heads, a matched cam and performance exhaust and leave the stock gear in there.
Put a Edelbrock intake and heads , a Demon 650 carb, cam and headers on a stock 350 chevy...then leave the 3.07 gear in there??? Then complain that it doesnt pull good down low. Put a 3.55 gear in it and it's a different car...no kidding. And it's so easy to do on a bike compared to the motor work...I like the gear on a stock 88 with pipes and a/c also..really nice..."a kick-ass mod"
 

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Still in one piece
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269 Posts
hdfat2002 said:
Greetings,

So having been planning it for a while, the planets finally aligned in such a way as to actually allow me to perform the primary gear change I hear everyone raving about--commonly referred to as "3.37 gearing."
-Fat
I've been thinking about doin' the same thing. Did you use HD parts and what was the cost?
 

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Registered
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73 Posts
Does any one have the gear ratios listed for different primary sprocket combos?
All i have ever seen is for stock primary and different trans/wheel sprocket combos. I was thinking of changing to a 24 tooth front primary sprocket but not sure if that would get me anywhere.
(Edited)
Hey I figured it out! Just changing to a 24 tooth primary would give me 3.28:1 final,about half way between. Does anyone think this would make any difference or just like kissing your sister?
 

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Restless
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1,672 Posts
Gomer said:
Does any one have the gear ratios listed for different primary sprocket combos?
All i have ever seen is for stock primary and different trans/wheel sprocket combos. I was thinking of changing to a 24 tooth front primary sprocket but not sure if that would get me anywhere.
(Edited)
Hey I figured it out! Just changing to a 24 tooth primary would give me 3.28:1 final,about half way between. Does anyone think this would make any difference or just like kissing your sister?
I think the problem you'll run into is too much slack in the chain by going to just a 24 tooth comp sprocket.
 

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Yea thats another thing I was wondering, if you could adjust for that or not, good point. I was thinking that it would be easy and you might see a slight difference.
 

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0043--Licensed to Doof!
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4,369 Posts
Hey I figured it out! Just changing to a 24 tooth primary would give me 3.28:1 final,about half way between. Does anyone think this would make any difference or just like kissing your sister?

That depends....... how cute is you sister??? :bleh: :roflback:
 

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Premium Member
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3,122 Posts
Gomer said:
Does any one have the gear ratios listed for different primary sprocket combos?
All i have ever seen is for stock primary and different trans/wheel sprocket combos. I was thinking of changing to a 24 tooth front primary sprocket but not sure if that would get me anywhere.
(Edited)
Hey I figured it out! Just changing to a 24 tooth primary would give me 3.28:1 final,about half way between. Does anyone think this would make any difference or just like kissing your sister?
Kissing your sister.
 

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Iron-Butt Hardcore
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212 Posts
Discussion Starter #11
fresnohog said:
I've been thinking about doin' the same thing. Did you use HD parts and what was the cost?
I went with OE parts. Pomona Valley HD in Montclair, CA gives me a 10% discount. You have to get a new primary cover gasket, too. I also installed a SE clutch spring since I was in there. There's a lot of hoop-la about "reduced effort" clutches lately--but I don't find the OG clutch with SE spring objectionable at all. For reference:

Clutch Basket PN: 37846-99A List: $320.00
Compensating Sprocket PN: 40269-85A List: $63.50
Primary Cover Gasket PN:60539-94B List: $30.50
SE Clutch Spring PN: 37951-98 List: $24.95

Total (at list price): $411.95 (+tax and a quart of whatever oil you use in your primary)

Many dealers will give you a discount. I got all the above parts, and the remainder of what I needed for a 35,000 mile service, for $372.76, out the door.

Again, this is a kick ass mod--for a stock bike or otherwise.

-Fat
 

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Still in one piece
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hdfat2002 said:
I went with OE parts. Many dealers will give you a discount. I got all the above parts, and the remainder of what I needed for a 35,000 mile service, for $372.76, out the door.

Again, this is a kick ass mod--for a stock bike or otherwise.

-Fat
Thanks. Sounds like I'll be doing it soon.
 

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Premium Member
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3,289 Posts
Gomer said:
Hey I figured it out! Just changing to a 24 tooth primary would give me 3.28:1 final,about half way between. Does anyone think this would make any difference or just like kissing your sister?

I believe if you change over to a 24 tooth sprocket, not only the chain slack could be a problem. The 'angle' of the chain towards the sprocket will change too and very likely the chain tensioner shoe will not be in full contact with the chain anymore. BAKER supplies an redesigned chain tensioner assembly with their 28 tooth sprocket set (included in DD6 gearset) to address exactly that problem.
About your sister, post a pic and I may comment......:dunno:

just my $0.02
 

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Highly Seasoned Rider!
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4,884 Posts
I believe that my 1993 FLHS Evolution was geared around 3.37:1. I ran a sidecar on it for several years and I recall it was good sidecar gearing and very lively from stop lights. It was revving rather high in the road, however.
I also recall that a fellow that I used to ride with had a 1993 Softail Deluxe and it was geared noticeably higher than my FLHS.

There is no free lunch on gearing. It's either one way or the other. Harley gears bikes for the type of usage that they envision for the particular fleet to which the machine belongs. That's why they choose the higher 3:15 or so for the FL touring bikes.

I don't have a dog in this fight since I tend to leave things stock. If it makes for better stop light drags, I guess it's OK. :)
 

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Restless
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Yeah, I've beat myself up somethin' terrible trying to decide whether or not to do it. I've got a leaking shifter shaft seal. I've ordered the primary gasket set and shifter shaft seal from Cometic. Whats just killing me is tearing everything down just to replace that damn seal. I really would like to make the labor of the repair more gratifying.

I guess the bottom line for me is that as much touring as I do the mod ain't worth it. I don't want to be the guy that's stopping for fuel all the time running 3.37 when the other baggers are runnin' 3.15.

I don't think I've ever been so wishy washy on something in my life!
 

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Nice to ride again :-)
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1,802 Posts
timbo said:
Yeah, I've beat myself up somethin' terrible trying to decide whether or not to do it. I've got a leaking shifter shaft seal. I've ordered the primary gasket set and shifter shaft seal from Cometic. Whats just killing me is tearing everything down just to replace that damn seal. I really would like to make the labor of the repair more gratifying.

I guess the bottom line for me is that as much touring as I do the mod ain't worth it. I don't want to be the guy that's stopping for fuel all the time running 3.37 when the other baggers are runnin' 3.15.

I don't think I've ever been so wishy washy on something in my life!
Well if you have the money for the parts, and those retail prices less 20% would put you in 340 or so I would guess, and your going in anyway, go for it.

Don't be left with that "I should have just done it while I was there" thing. The next cover I crack, cam, rocker, or primary, I got something I wanna put in. I made up my mind and just will bite the bullet, life's short. :hystria:

I am not sure your fuel consumption would be that big of a deal, hell 125-140 miles and it is time for a snack anyway :bleh:

I have seen calculations posted a bunch and it seems minimal each way on paper if I remember right.

Hell go for it and let us know seat of the pants what you think.:whistle:
 

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Average Dude
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6,263 Posts
Well, if you have the bucks and want the best of both worlds, why not do the gear change and add a DD6 six speed tranny. That would give you the lower gear ratio and you would have the overdrive which would put you back at near stock 5th gear rpm/speeds. I haven't done the math, but it sounds plausible.

Anyone else already do this, or have any thoughts?

YB
 

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Premium Member
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3,122 Posts
timbo said:
Yeah, I've beat myself up somethin' terrible trying to decide whether or not to do it. I've got a leaking shifter shaft seal. I've ordered the primary gasket set and shifter shaft seal from Cometic. Whats just killing me is tearing everything down just to replace that damn seal. I really would like to make the labor of the repair more gratifying.

I guess the bottom line for me is that as much touring as I do the mod ain't worth it. I don't want to be the guy that's stopping for fuel all the time running 3.37 when the other baggers are runnin' 3.15.

I don't think I've ever been so wishy washy on something in my life!
Excuse me Timbo but that change is only about 7%. I'll leave the rest of the math on gas mileage up to you.
BTW I used to get 45-50 with cams, AF, pipes, PC, stock gearing.
Now with 95", 3:37, well over 100/100 and get 42-46.
I'll admit I don't ride hard but do alot of 2 up.
Gof for it.
 

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Iron-Butt Hardcore
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212 Posts
Discussion Starter #19
timbo said:
I guess the bottom line for me is that as much touring as I do the mod ain't worth it. I don't want to be the guy that's stopping for fuel all the time running 3.37 when the other baggers are runnin' 3.15.
I don't think you'd regret the 3.37 swap. I rode twisties today two up (first time since the swap) and I was at 140 miles when the light came on. My light comes on, BTW, when I have used a little less than 3.5 gallons. So that's somewhere around 40 MPG on the new gears. Not stellar, but I still have tuning work to do.

Besides, after a buck-and-a-half, it's time for a break anyway!

-Fat
 

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3,289 Posts
YankeeBob said:
Well, if you have the bucks and want the best of both worlds, why not do the gear change and add a DD6 six speed tranny. That would give you the lower gear ratio and you would have the overdrive which would put you back at near stock 5th gear rpm/speeds. I haven't done the math, but it sounds plausible.

Anyone else already do this, or have any thoughts?

YB
I have a DD6 and it comes with a taller primary sprocket to compensate for the 1:1 direct drive sixth gear and bring it back to a OD6 overall gearing. You can leave your original sprocket in and get the back the stock overall gearing but spread over six gears. Maybe interesting for a high revving, high HP TC with little low end in the mountain areas. For everything else IMHO too much shifting for nothing. Check with the Baker website, they have a pretty cool gearing calculator

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