2001 Ultra Sprocket change?

Discussion in 'General Harley Davidson Topic' started by Mikvi, Oct 7, 2015.

  1. Mikvi

    Mikvi Member

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    Just finished a hi-torque pork rebuild on my 2001 Ultra Classic. Now it has tons of torque and revs like a 4 cylinder if I get on the throttle too much :) As I am building it for cruising, I want to raise the final gearing, and I figured the cheapest way was a larger engine sprocket. I have done this many times with chain driven bikes, but this is a first for me with a belt. I'm looking for advice and suggestions as to what I need and what is involved. I am currently running standard sprockets (32 teeth I think) and was considering going up by 2 teeth. Would this require a different belt?

    Thanks
     
  2. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

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    Some time back someone had a similar question and dolt explained it quite well in great detail. If I remember correctly there was pros and cons for what you're asking. Hopefully he'll see this post and respond or you can PM him.
     
  3. Jack Klarich

    Jack Klarich Expert Member

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    If I understand your question you are changing the primary drive ratio? You will most likely need a new chain JMO
     
  4. dolt

    dolt Senior Member Contributor

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    Back in 1999, 2000, and 2001 HD introduced the Twin Cam engine on touring bikes with either a carb set up or an EFI option. HD introduced those EFI bikes with the MM EFI throttle body. The carb Touring Bikes were given 3.15 gearing and the MM EFI Touring Bikes were given 3.37 gearing.

    IIRC, your bike is EFI which means you have 24/37 primary gearing and 32/70 secondary gearing for a final drive ratio of 3.37 which is why you feel like you need to drop cruise rpms. The motor is probably spinning about 3200 rpms at 70mph, which BTW, you might not like :cry but does no damage to the motor. As a matter of fact, the motor likes it.:D

    The carbed bikes have 25/36 primary gearing and 32/70 secondary gearing for a final drive ratio of 3.15 which I find perfect for my '02 FLHT.

    So, you have two options; you can replace the primary gearing with a 25T motor sprocket and a 37T ring gear/clutch basket and leave the secondary alone and drop cruise rpms at 70mph by about 200. Bad news is initial cost but there is a market for the 24/37 primary setup. The good news is less labor intensive to make the change; removing the primary chain case cover exposes the primary drive. Additionally, no need to adjust the speedo.

    Next option is the replacing the 32T trans pulley with a 34T piece and replacing the 139T belt with a 137T belt. A two tooth change, up or down usually requires a belt change. Good news is this is a bit cheaper but much more labor intensive; requires the removal of the outer primary, inner primary, rear wheel and dropping the swing arm to R/R the belt. Addtionally, you will need to purchase a piece of hardware to adjust the speedo as it will no longer be correct.
     
  5. Breeze3at

    Breeze3at Well-Known Member

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    Great post by Dolt, but the belt needs more teeth (longer), not less. Bigger front sprocket = larger diameter = more teeth.
     
  6. dolt

    dolt Senior Member Contributor

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    Good catch, typo. I just got the belts backwards.:small3d015: Also changes final drive ratio to 3.17 which affects rpms in every gear and just a bit taller than the 3.15 final drive of stock.:s
     
  7. Mikvi

    Mikvi Member

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    Dolt

    Thanks for the info. This is a project bike (fuel injected) which will be stripped down for paint this winter. While it is being painted, I'll change the engine sprocket. I have plenty of torque and would expect slightly better fuel economy with the switch. The bike has 30,000 miles and is probably on the original belt, so a change would be good. Planning a 4,500 mile trip up the East coast next Spring.

    PS where to get a 141 tooth belt?
     
  8. dolt

    dolt Senior Member Contributor

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    First let's get the lingo straight. The pulley you are referring to as the "engine sprocket" is the trans pulley. Motor sprocket and main shaft sprocket are inside the outer primary and drive the tranny. The trans and wheel pulleys are exposed and drive the rear wheel.

    Unfortunately, I don't believe anyone makes a 141T trans pulley and if you do find one, it will be aftermarket which I do not recommend; too many get broken. The OEM belts are more expensive, made by Gates but to the MoCo specs. For example, there is a 140T offered by JP Cycles and the manufacturer is listed as "Gates by BDL", so I don't know if this belt is manufactured to the MoCo specs; it sells for $141. The OEM PN for that belt is 40024-09A and it sells, from a discount dealer, for $220. Given the choice and considering the work involved in replacing a belt, I would pay the premium for the HD belt but that's me.

    The tooth pitch on the trans pulley is 14mm, so two teeth = 28mm. Your current belt is 139T (disregard the 137T to 139T comment in my previous post, I was thinking FXSTD and not my FLHT). Anyway, adding one tooth to the belt reduces the difference between the 28mm added by the 34T pulley to 14mm by the added 14mm on the belt. A bit of bad news though, if the 140T belt (or a 141T if you can find one) will only be available in a 24mm belt. Doesn't mean you have to change the wheel pulley but it would be a good time to do it which would allow up to a150mm tire on the rear in the future. A new rear wheel pulley is going to run near $200.

    A larger pulley is going to require that the axle move forward at least 14mm, plus some additional for slack to fit the belt over the wheel pulley, let's say another 8mm just for sake of this discussion. So, if you currently have say in inch of space to move your axle forward, the 140T belt will work; if not, it won't.

    I am going out on a limb here and suggesting to you that you forego the trans pulley change for a couple of reasons:

    1. I doubt that the 140T belt will fit but maybe it will. I suppose you could order one, try to fit and return if it doesn't but that's a lot of work only to discover that a 141T belt is required and may not even be available.

    2. If the 140T doesn't fit and you can't find a 141T, you have to put everything back together again and punt or decide to change out the 24/37 primary to the 25/36 to get the same results as you would with the 34T trans pulley.

    3. There is an option to modify the swing arm for more adjustment travel which adds cost and downtime but is an option and would allow the use of the OEM 140T belt.

    4. You will need to spend another $100 plus for a speedometer recalibration module to correct your speedo which is affected by changing the secondary gearing.

    I suggest that you carefully weigh the trans pulley change against the primary drive change. Much less labor involved; you can get it done in a couple of hours. Cost will be about $500 for the motor sprocket and the clutch shell& sprocket/ring gear/bearing and retaining ring; no need to change chains. No need to recalibrate speedo for primary gear changes either. You retain your secondary drive; trans pulley, wheel pulley, belt and replacement belts, should you ever need one, are OEM and readily available.

    Just food for thought; good luck on the project.:s
     
  9. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

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    I've been following this post and have to ask, is all the cost and work really worth it to only reduce the rpm's by about 200?

    As dolt said, these big twins like rpm's and for the little your going to gain it hardly sounds like it's worth the effort. JMHO.
     
  10. dolt

    dolt Senior Member Contributor

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    Valid question and one the OP should carefully consider. Perhaps snag a ride on a buddies bike, pre-six speed, with OEM 3.15 gearing to get a feel for the difference. Not really a fair comparison since he now has more torque from his recent motor upgrade but 5th gear, at a steady rpms will be the same.

    I wanted more torque multiplication in my FL but didn't want to give up the 3.15 final drive in 5th gear. Installed the Twist Gear kit and picked up 10% torque multiplication, plus a close ratio four speed but retained the 1:1 in 5th gear for the 3.15 final drive. A gearing change can make a huge difference, for as many like the OP that thinks a 200 reduction in rpms will make a difference there are more that would like the reverse, changing the 25/36 primary to his 24/37; he would have no trouble selling his primary hardware to recover some of the cost. Something I should have included in my last post.

    Subjective and personal goals for sure. What might make sense to one, makes no sense at all to another and how and where we ride is also a factor.