23T trans sprocket

[JW113]

It's been a while since I re-geared an Ironhead, but I kind of recall that 23T is the biggest trans sprocket you can install without the chain getting into the cover & such. That sound about right? Sure would like to drop the rpms a little at highway speed.

-JW

[tmwmoose]

Yeah I believe your right  stock was 21t

[garyajaz]

your both right. 21 is stock. when I put the 23 on I had to trim a few things under over. I was also using a wider o-ring chain. 
now, I would suggest a 22. since the 51 is riveted to brake and a bit difficult to change...lol.
we must work with the front.
using a fairly stock motor a 23 will be too much. hell I barely got  a third gear wheelie with the 23 on.
a 22 will help rpm but still give ya some grunt.
its not just like its a couple teeth.  its the ratio. you will be gearing it HIGH.
on a stock bike you will be disappointed with the accel and it wont pull top gear.

just last year or so ago I put a 22 back on cause was only street riding it and wanted more low end to play with all the new "fast" Harleys.

[JW113]

With the 21T stock sprocket, it's spinning 4400rpm at 75 on the freeway. That seems like a bunch to me, let alone having to hold on to the bars for a couple hour ride up the coast & back. Stock overall ratio is 4.21:1, pretty high and was probably fine in the days of 55mph speed limits when this bike was made. Out here where I live, other than rush hour, if you ain't going at least 80 you're likely to get your ass ran over.

So you don't think a stock motor will pull a taller gear? Here is a data point of 1 to compare. This mostly stock '78 XLH has considerably more torque than my '71 BMW R75. Give the sporty some throttle, it jumps. Give the Beemer a LOT of throttle, it says "huh?" and slowly gains speed. Now, mind you, BMW is an autobahn bike, and has no problem riding 100mph all day long, but getting up to 100, it sure ain't in no hurry.

Beemer is geared at 3.20:1. The sporty is geared at 4.21:1, a full point higher. Beemer has no problem pulling that much gear, and it makes less HP and TQ than the sporty. So I guess I'm not seeing the problem. Here's maybe one more data point. My Indian makes even less HP than the Beemer, and it's final ratio is 3.73:1. And it has no problem holding any speed in 3rd gear (top gear).

I can't help but experiment with this. Have 23T trans sprocket on order, and will order a 49T rear sprocket today. 23x49 will net a 3.70:1 overall drive ratio, bringing the rpms at 75 down to about 3800. That I think I can handle!

If it really has problems holding speed in top gear, time to add a turbocharger. 

-JW

[drifter]

Now you have to think this through.  If you add a turbocharger, aluminum, we all know how you can't stand aluminum that is not polished to mirror brightness, you won't have time to ride.  Spend all your riding time polishing, and polishing, and.....looks good though.   

[JW113]

www.ShineSeal.com



-JW

[garyajaz]

I am out of date.
I thought the 51 riveted rear was only sprocket available for drum brake bikes.
yeah, a 49 rear will make it even taller.
AND a 23 front?  how much power ya got?

55 speed limit when made?  lol when young that was a suggested speed limit for second gear.
4400 is not bad. they built to turn 6100 stock.

mine is set up for 7500

I toyed with turbos on irons.
tom sifton first mentioned to buy 3 sets of cases and 5-6 rod/cranks to have sitting around.

unless set boost to 1 it aint gonna last.

[JW113]

Just joking about the turbo! This 78XL is no hot rod, more of a work mule to get me back and forth to work.

PBI makes a 49T rivet on rear sprocket. Will be interesting to see how it works out. If not, can always undo what was done.

-JW

[garyajaz]

do you want the high  gearing to eliminate vibration or just cruse at lower rpm?
with a 23 and a 49 you are NOT gonna red line in 4th.
hell, will be lucky to pull it. in my opine
the 23-51 was really tall even for mine to pull top rpm.

got that c.v. carb going right?
I haven't moved my iron for weeks. healing slow, but getting some work done on hauler/garage.

[JW113]

I want to gear the bike better for highway speed. Seems stock gearing is more for drag racing! So yes, low the rpms for both less vibration in the bars, and less wear/tear on the motor.

I have the CV on, it's running pretty good (after it warms up!). I put a 170 main jet in, still seems a bit sluggish at full throttle, will drop that to a 160 tomorrow and test.

The problem now is the clutch drags such that getting into neutral at a stop is virtually impossible. Yeah, I know, it's an ironhead, they all do that right? Well, my other ironhead don't. Shifts like a dream and no problem finding neutral. I had installed a Tamer II, and tried different types of pri-trans oil, but no help. So, bought a set of new Alto steels & friction disks, will see if that helps. Oh, and try some Type F auto trans fluid in it.

-JW

[rider7816]

I have a relatively stock 1977.  I was having the same problem down here in south Florida with having too high of RPM's as there is mostly highways.  I ended up with the 23t gear and it goes just fine.  I weigh close to 260 and Im able to get going just fine and keep up with MOST traffic. 

I kept the original 21 tooth just in case but I think it may become wall art at some point

Frank

[Hillside Motorcycle]

Me thinks, that the giant gear change will not be welcomed.

[JW113]

Never know until ya try! If it sucks, can always put stock 21T back on. 23T puts it at the same gearing as a new 883.
Was out riding around on Saturday, have to sat the stock gearing sure does wind the piss out of that motor at freeway speed if you ask me.

-JW

[garyajaz]

the real problem is inside ratios.
on old sporties 123 were close ratio for hauling around town and chasing 750 Hondas.
hell, I even put on a 19 once for stop light stuff.
shook a lot of trees back in the day.
then a huge gap to 4th so a guy could actually highway with his 2.2 gallons.
mine never did any good till I got a close ratio 4th.
they always needed a 5th gear to keep rpm's up.
the big twins were just reverse.
when I got my 72 super glide it had the low gear of a john deer. (to get the baggers going, same tranny)
then a huge jump to 2nd and 3-4 were ok. I have old pix of me doing a wheelstand on my nearly stock 72 superglide.
at 74 inches.
my 03 95 incher wont bring it up in first like old one did.


(but 6 is just too many)

[JW113]

Weather was nice so spent the afternoon in the garage swapping in that 23T trans pulley. Have to say, it feels like a "normal" bike now! Instead of running out of rpms at next to no mph. Had it up to 100 on the freeway no problem, just about the point where my hands totally lost any feeling. At 80, though, it's perfect. Mine seems to get into the bad vibes in the bars at about 4400, and at 80, now it's right at 4300. At 75, it's as smooth as butter.

Don't know what to tell you Gary, maybe you been using too hot cams with no mid range torque?

-JW

[garyajaz]

my above post was about both my stock bikes.
when new the 74 sporty and the 72 super.
just how the inner ratios are.

now?   torque on the iron is "adequate". its just where I want it to top out in rpm at and which gear does better wheelies...lol  is how I gear it for that time. I have, in stock, from 18 teeth to 23 teeth.
but my rear is fixed at 51.
also keep in mind the belt drive  ratio is different than stock. its higher from the start.

[JW113]

Yeah, I was referring to when you told me a 23T would be too much. Seems just right to me, but then I don't plan on any wheelies.    Just need to keep up with freeway traffic and not have my hands go totally numb in 5 minutes.

Here is where the speed/rpm ranges are. Overall drive ratio is 3.85:1, basically same as a evo 883.

[attach=0]

-JW

[garyajaz]

looks good on paper. will it pull 6k in 4th with that gear?
or just a "overdrive"?

[JW113]

I had it up to 100 (briefly) in 4th, which is around 5400. Felt like there was more in it, but dropped back down to 80 before I attracted unwanted attention.  6000 is pushing 115mph, not the kind of speed you want to get caught at around these parts. Perhaps this spring I'll take it down south of Hollister, where these are a few nice long and flat stretches on Hwy 25, and see what it tops out at.

-JW

[garyajaz]

you are right there. lol
I remember the bay area being somewhat crowded 40 years ago.
cant imagine it now.
out in southern desert sounds like the way to test.

I about 14 miles from a flat, long, straight, fenced desert road with 30 miles of no cross roads.
it leads to a prison so no radar or cops. its my top end test road.
great fun on the buell.

good you getting it out and stretching legs. 100 on a 70's iron with a cv is good.
hell a 70's ironhead that runs is cool in my book.

[Ivan RoachCoach]

I've been running a 23-toother on my '74 for about seven years now & it is THE "Potty mouth"!       

No slouching or lagging whatsoever around town, higher top speed for passing those semis on the on-ramps to I-95 & it feels like an overdrive at 80-plus.

Get a quality one, like a PBI.
I didn't have to clearance (grind away) on my sprocket/kicker cover at all, maybe because I'm not running an O-ring chain.
Not that it would've been a big deal --- it's one of the old, tough-bastard OEM ones.     

[JW113]

Wow, activity on the Ironhead forum!

Yes, the 23T is a nice gear. And I do use PBI exclusively. It's either that, or a V-Taiwan sprocket, no thanks!

Am actually considering a 22T. I just don't get out on the open road with my Ironhead, mostly in town riding for commute. That first gear is a bugger to launch from a stop with a 23T. After that it all good, but you have a 3speed with overdrive. 22T might be a nicer compromise. What the hell, why not give it a shot and see?

-JW

[garyajaz]

Am actually considering a 22T. I just don't get out on the open road with my Ironhead, mostly in town riding for commute. That first gear is a bugger


see post #2
I been at this ironhead stuff for 44 years...