Final drive belt to chain conversion

[96flhpi]

I've got a tranny main shaft seal leak (I think - whatever it is I've gotta pull the primary to check it out) I'm gonna address in the offseason.  While I was in there I was thinking about converting my belt final drive to chain so the next time she leaks it won't be a big concern.  Anyone know if it's a simple sprocket swap, or would I need a new tranny mainshaft and rear wheel as well?  Bike is an '82 FLH with stock cowpie.

Thanks in advance,
Vin

[Lew]

Not a problem Vin it's a straight swap out.  The only thing to look out for is the chain running too close to the tranny.  Some have that problem some don't.  Might have to run a spacer behind the sprocket is all.  A .060 spacer usually does it just fine.
Lew

[96flhpi]

Awesome!!!  Thanks for super quick reply Lew - and for giving me the answer I was hoping to hear.  Saw the spacers in the catalogs when I was looking to see if they'd give me info on whether sprocket would be a direct swap - no info in cat. but luckily plenty of info here.

Gonna consult my service manuals to see if they list stock gearing (tooth #).  If not, I know someone here will know.

Thanks again,

Vin

[Lew]

I beleive stock sprockets for your FLH are 22 tooth tranny and 51 tooth rear.
Lew

[96flhpi]

Right on the money, Lew!!  Saw it in my manual.  Actually what I really need to know is chain info - don't see anything about stock length.

Also, am I correct in thinking if I run the 23 tranny spr. from a FX it'll drop the RPM's on the highway a bit and I could still use a stock chain?  I'm not looking to race anyone.

Thanks again for your quick answers.
Vin

[Lew]

Sure you can play with the gearing some.  I think you will need a 102 link chain.  You can go longer than that and shorten it too.  Only thing I can add is to go with a good quality o-ring chain.  There are several available and some are better (and more expensive) than others.  I've had good luck with EK and Tsubaki....not so good with Diamond.
Lew

[76shuvlinoff]

  I don't know what your motor sprocket is but if it's a chain primary with a 24 tooth motor sprocket I'd suggest you go to 23 on the tranny maybe 49 on the rear wheel.  This is what I ran on my 76 with a stock-ish mill. That 22/51 can pull stumps but coming off a stop it's about 3 pops and shift.  For me it was way too low for highway cruising.
   Whatever chain you get, don't skimp there.

[96flhpi]

Thanks for replies.

Looking at prices it seems I could go top of the line with everything for a chain and sprockets and still be much cheaper than replacing the belt and two pulleys.

What I meant was can I use the stock length chain if I only go up (or down) a tooth or two?  Also wasn't 100% sure I was thinking clearly about whether larger or smaller tranny sprocket would = lower RPMs but did some research and found out my brain does still work, a little at least.

Thanks for the chain brand advice, Lew.

76 - it is a chain primary - don't know what motor sprocket but I guess I'll find out when I pull it apart.  Thanks for gearing suggestion.  I know I saw a RPM calculator somewhere but of course I can't find it now.

Thanks again guys.
Vin

[Lew]

The engine sprocket will most likely be a 24 tooth.
As an after thought........check the tranny case studs for leakers.  I've seen them leak just like a bad mainshaft seal.  Good luck!
Lew

[76shuvlinoff]

 If it's all apart try the 23T tranny sprocket.  It gives you more options later to play with the easy-to-change wheel sprocket.  From everything I've read going to 24 at the tranny will make things real crowded in there especially with an O ring chain.

.02

[FLHS 1]

If you have a factory rear belt drive your rear sprocket should be 70 teeth. The transmission sprocket should be 33 teeth and when combined with a 24 tooth engine sprocket, will provide a 3.27 final drive ratio. To achieve close to the same gearing as you have now, you will need a 24 tooth transmission sprocket  with a 51 tooth on the rear wheel. A 49 tooth rear sprocket will provide a 3.14 final drive ratio; nice for Hwy cruising, if you have the horsepower to pull it.

[fulldress79]

Another source of a leak is the main drive bushing (just been there done that) Mine was so loose,it there was a "knock" coming from it at idle.

[96flhpi]

Nothing's apart yet, not ready to concede that the season's over.  Probably should since I'm always thinking about that oil splattered belt giving up whenever I go for a putt. 

Like I said I only think its the mainshaft seal.  Wherever leak is coming from it's behind primary so it's gotta come off no matter what it is & I'll figure it out from there.

Thanks for info FLHS - I was planning on trying to figure out what would be closest to stock gearing and go from there but you saved me the trouble of asking (or trying to do math).  I guess I'll take 76's advice on the 23T, though, since an o-ring chain is in the plans.  Seems like 23/49 would get me close to gearing I've got now, not as close as 24/51 but I could live with it. 

Thanks again for all the help, time to hit the catalogs.
Vin

[Lew]

FYI  The rear belt models are notorious for wiping out the main gear bushing.  The belts contract when they get warm.  Just when you (and eveyone else) thought it was adjusted right, it was actually running very tight and taking out the bushing....very common....
Check the mainshaft carefully for any lateral movement.  Any movement of the mainshaft from a worn bushing will take out the seal and you'll soon be right back where you started.  Good luck!
Lew

[96flhpi]

Will do - thanks for heads up!

[randallwhitman]

I'll bet you that after a year or two with your chain, you'll wish you still had the belt.  Just a guess.  I've had both.  I'm lazy and the chains all make a mess.  Plus, they're noisy.  Plus they require maintenance.....lubing and adjusting.  The belt drive is one of the best advances the moco made, I think.

[96flhpi]

I hear ya Randy, belt sure is nice but I don't trust the oily belt that's on there now so I've gotta change it.  From what I read I should use new pulleys with a new belt.  If I'm wrong someone let me know, but I assume oil would deteriorate the rubber in the belt - let me know if I'm wrong about needing new pulleys as well.

For a little more than the price of a belt alone I can get a top of the line chain and both sprockets.  For the price of a new belt and pulleys I can get the chain system and the CV carb that was in my plans for the winter.

More importantly, if I replace the belt and she starts leaking again in the next few seasons I'm gonna be pissed.  If I convert to chain and she starts leaking again - well, I could always add more oil, can't I?  All of my bikes prior to the EVO I bought in 2000 were import cruisers with chains.  Mess was sure annoying, but maintenence wasn't a big deal.

Vin

[Lew]

I typed out a long spiel about the pitfalls of factory rear belts and lost it in cyberspace.....probably divine intervention doing us all a favor.....
Basically, the main problems encountered with them on shovels is the fact that they were made to work in a chain drive application.  Problem is the course splines on the four speed mainshaft and the greatly offset tranny pulley.  The pulley, being so offset is trying to pull itself off the shaft when under a load.  Along with the course splines on the mainshaft, this happens.  The stock tranny pulleys were/are very soft and will self destruct over time.  All this is very hard on the mainshaft bushing.  Add to this the fact that the factory belts would tighten up when run....instant bushing/seal problems and leakage.  Oil and belts don't mix...period.  What most everybody ended up with was a very expensive mess that until recently was fruitless to try to repair.  Until Supermax started producing tranny pulleys and belts that did what they are suppost to without the inherent problems of the factory junk, the best option was to convert to chain.  Quick, cheap, easy and works with no BS.  Even with the improved parts now available you are still stuck with chain drive engineering modified to work with a belt...same splines allowing the offset pulley to squirm and the resultant massive load on that old bushing still taking out the seal/s.
And now I must rest.......
Lew   

[biggerjose]

Howdy;
  I have read all of the above posts and it looks like the thing to do here is get a light weight tranny pulley from Super Max. www.supermax.net Take your tranny apart and replace the bushings with the 1980 to 84 5 speed bearings and seals. This requires a perfect mainshaft, probably a new one and the early model 4th gear would be required as
pre 77 4th gear as the bearings are different than the 78 and later. The 4th gear can be machined out to accept the bearings. The bushings were never leak proof like the later bearings and seals...Big improvement for sure.
     The stock tranny pulley is so friggin' heavy, they tear everything up just with the shear weight. (6 to 7#)
  To fix the leak is the best thing. The Torrington bearings in your tranny case can be retrofitted back to the early loose roller system. Those are only about 1/2" long where the loose rollers are around 1" long.
  I have had a rear belt for years and years and I have also had a chain drive for years and years...No more chains...They indeed suck. Jose

[Lew]

Replacing the bushing with bearings would be one improvement to help with oil control.  One problem I encountered is the main gear is too hard to properly machine to fit the bearings...without using a post grinder (expensive).
And again the root problem....the squirming offset pulley on course splines...no matter how light and tough the pulley is.  Compare these early belt drive designs with what is being done today...big difference with many changes to make it work reliably.  The moco didn't get it right until the early 90s.  Now you see very fine splines on the mainshaft to eliminate the squirming of the offset pulley.  The pulleys are not offset nearly as much as the old design.  Much better pulley retention than the old design.  Bearings instead of bushings, with the mainshaft raised to ease stress on the shaft, pulley and bearings.
I once contacted Andrews concerning the manufacture of four speed main drive gears with the later bearings installed.  I was curious to know why it wasn't made available from them as an upgrade, option or standard.  I was told they consider it a compromise to the integrity of the part and they would not produce something that was a liability.
I've found over the years that those that converted their rear belts to chains didn't do it because they thought chains were better.  If they thought that they sure wouldn't have paid for belts when they bought their bikes.  It's because they were tired of fighting them, saw the light and wanted to ride.  Myself included.
Lew

[shovelbill]

this may be of some help to you.
http://www.bakerdrivetrain.com/gearratios/index.htm
good luck with your project.

[pappyfreebird]

bushings seal n 23-48 sprocket combo - 102 link oring  n freak at the difference on the hiway youll love it n so will that motor

[96flhpi]

You OK Pappy? - I didn't have to translate that post.  You're not taking it easy on me cause I'm a Yank, are ya? hahaha

Seriously thanks for the info - was wondering if that 23-48 combo might be too steep for stock engine and clutch.  Any thoughts, anyone?  Sure would like to run it if she can handle it.

Thanks for link Shov-bill, and thanks for info Lew - good stuff to add to the ole noggin.  Like I said I'm interested in chain cause I won't be too concerned if she leaks again. 

Thanks again to all who replied!!  Looks like winter's here - soon as my back stops acting up gonna start pulling her apart, got a rocker cover leak to take care of as well.  You'll be hearing from me soon enough - "how do I get this damn stuck comp. sprocket nut off?"  Hahaha
Vin

[MBSKEAM]

what about this?



mbskeam

[76shuvlinoff]

  I ran 23 /49 on a 74 inches with a 4 speed, it was fine then I went to a 5 speed and a 93 inches and dropped to a 48 sprocket. I "think" you'd be ok with a 23/48 on a stock-ish set-up but it all depends on how you like to ride.

[pappyfreebird]

stock 79 fxs 23-48 fer lil ova 10 yr (same clutch n looks like new) had me 79 flh (had steeper 1st since baggar) ran 23-48 fer bout 5yrs still has that combo but the icemayun leaves it sit in garage...ifn yo do lotsa a stop n go n want most power kin git,,well then build a 93" er wahahaha ,,but in all normal stop go n great on hyway..ya kin tell she takes mo clutch werk ta git er movin ..but that combos been round ,well longer then me hows that

[biggerjose]

You know, you can install a 2.60 to 1 1st gear if it struggles in 1st. Have done the bushing to bearing conversion. You just have to find the right machinist...No problems. Andrews probably would rather U buy a 5 speed...Not really necessary...5th and 4th are both 1 to 1.
  Agreed, some pulleys don't fit the splines right...Just buy from the right people..There are "Some" people that make good fitting pulleys...Jose

[Reddog74usa]

TTT

[hotham]

Before I retired I was a mechanical engineer that designed drives all the time.  When the Gates Polychain was invented, it finally allowed a belt to replace a chain.  Belts were designed to operate at higher rpm and chains were used in slower, high torque drives.  Still in a chain drive running enclosed and in oil, like your primary, they are almost bulletproof.  An "O" ring chain is very good, but not as good as an enclosed chain.  Belts are clean running and when adjusted and aligned are very reliable.  The big problem is you can't fix a belt problem on the road as easy as a chain.  I am convinced that most primary belt drives are installed because they loook "cool", not because they had problems with their chain drives.  But, you spend your money and take your choice.  I am convinced that the Gates Polychain belt is the best.  I have designed Polychain drives for 1000 hp applications and they worked great.