6 speed tranny's for Harley's

[bob_e95482]

I have a RevTech 4 spd in my '73 84 in. shovel. I have it overgeared (48t vs 51t rear). Cruises good. A little slow off the line, but worth the tradeoff to me. The OD is to lower RPM while cruising. My 4 1/2" stroke gives me enough torque to overcome the gap between 3rd & 4th. My $.02.

[harcosparky]

On the lower displacement engines like your puny harley, true there isn't much point getting the 6spd, though on my IronHorse texas chopper running a 124 CI with alotta extra torque and zoom power it's nice to have the extra gears.....

You'll need all the help you can get just to try and keep up with the Suzukis.

Maybe you could rip a 13 speed tranny out of a Kenworth!

[moe1942]

The point missed is extra gearing means lower RPM's which equate to longer engine life. The extra gearing evolved due to interstate travel. Plus there is no law that says you have to use all six gears all the time.

Those who are more mechanically inclined will understand what I have said..

Stick with your three speeds and keep that puppy wound tight.

[burninbriar]

Hey Pete,
The need for a six speed comes in when the engine builder builds an engine with a very narrow power band. Some guys like a cam that is quick reving and builds power real fast so you get super quick acceleration but with that you loose power quick as well so time to grab another gear. Now on your mostly stock 80 incher that has a cam that builds nice power over a real wide range, if you were going to go after some ricers you would most definitely need to change the cam and rework the heads, change the rods and get that 6 speed. In 94 I won the Easy Rider horsepower shootout with my 80 incher and Skeeter Todd on the seat from Easy Rider(121hp at the tire). This thing would eat CBR 600s, but was no match for the CBR 800's.
Good luck,
Bulldog

Thanks Bulldog;
Thats the kind of stuff I was after. I was thinking along the lines of a heavy load or pulling a trailer, but I've been loaded very heavy with my 80-CI 4-speed and pulled a trailer,(not at the same time though ) and did just fine with 4. On the speed end only, it would seem that unless you plann on 300 mph, 6 speads is not really needed.
The only argument I would have with you're explanation,( and it is a factless argument since I never ran a big inch 6 speed ) Is that you would wast too much time shifting gears to keep it in a narrow rpm range to win races.
How tight of a power band can you really get on a big inch Harley ?

I did recam mine, first with an ev-46 then changed to an ev-13 witch I like a lot better. Its more of a dresser style cam, a lot of low and mid range performance. I'm also running 10 /1 pistons but that is not by design, thats all I could get in a 15 thousanth over (long story, I think I have the last set in existance) , I wanted to keep a low compression. The 10 / 1 pistons CCed to only 9.3 / 1 when it was finnished so I'm OK with that.

[harcosparky]

The point missed is extra gearing means lower RPM's which equate to longer engine life. The extra gearing evolved due to interstate travel. Plus there is no law that says you have to use all six gears all the time.

Those who are more mechanically inclined will understand what I have said..

Stick with your three speeds and keep that puppy wound tight.

You don't understand these " harley " types. Lower RPM = Lower Exhaust Noise. They need em wound tight to be LOUD !!!!


Side Note - I own a Harley - fully restored STOCK 1972 XLH 1000 - not ridden much if at all - it's a Harley after all!

[burninbriar]

The point missed is extra gearing means lower RPM's which equate to longer engine life. The extra gearing evolved due to interstate travel. Plus there is no law that says you have to use all six gears all the time.

Those who are more mechanically inclined will understand what I have said..

Stick with your three speeds and keep that puppy wound tight.

Adding more gears is not the only way to lower the rpm. I lowered mine 300 rpm just with a final drive sprocket change. With all the the available horse power the Rpm range could easily be covered through 4 speeds and eliminate skipping gears as you mentioned. Like I said earlier, I end up skipping gears with my 4 speed, if I had a 6 speed I would be skipping 2 at a time. The first 5 is just bringing it up to direct drive like the 4 speeds.
I like Bulldogs explanation so far, it makes the most sence.
By the way, they do make 3 speed drag transmissions, I just don't know any one useing them.

[harcosparky]

Adding more gears is not the only way to lower the rpm. I lowered mine 300 rpm just with a final drive sprocket change.

Yes final drive ratio change is the easiest and least expensive, but it affects performance in all gears. I would imagine the extra gear or two would act as an 'overdrive' for highway use, leaving the final drive ration alone leaves lower gear performance intact, while adding an extra gear or two would give you more flexibility.

Having the extra gear and not needing it is better then needing it and not having it. I have a Suzuki with a 6 speed tranny - rarely does it get out of 4th but when hit the interstate those gears are nice.

[burninbriar]

Yes final drive ratio change is the easiest and least expensive, but it affects performance in all gears. I would imagine the extra gear or two would act as an 'overdrive' for highway use, leaving the final drive ration alone leaves lower gear performance intact, while adding an extra gear or two would give you more flexibility.

Having the extra gear and not needing it is better then needing it and not having it. I have a Suzuki with a 6 speed tranny - rarely does it get out of 4th but when hit the interstate those gears are nice.

Thats why I changed my 1st and second, I'm giveing it a wider range of rpm. 1st will end up virtually the same as stock and 4th will lower my rpm by 300 at 75 mph.
I guess with belt drives you are some what limited as to what you can do so I might see an argument there.

[fun4now]

i would think the 76 speed (if geared propery) would be an advantage if you were intending to pull a trailor with it, especily if mountans were involved. nothing like croozzzzzing the mountains for great views. i have ridden from florida to NY on several ocations and have to say the pensilavinea mountains was about the best part of the trip, well the bikinies in Fl. were not too bad eather.
the 6 speed could be set up to give you much better towing. it realy depends on what you want out of the bike and what you are willing to do (and spend ) to get it. if i was going to be pulling a trailor i would want the extra gears, you could always skip a few when not towing.

[burninbriar]

i would think the 76 speed (if geared propery) would be an advantage if you were intending to pull a trailor with it, especily if mountans were involved. nothing like croozzzzzing the mountains for great views. i have ridden from florida to NY on several ocations and have to say the pensilavinea mountains was about the best part of the trip, well the bikinies in Fl. were not too bad eather.
the 6 speed could be set up to give you much better towing. it realy depends on what you want out of the bike and what you are willing to do (and spend ) to get it. if i was going to be pulling a trailor i would want the extra gears, you could always skip a few when not towing.

76 speed ?
I agree it could come in handy totin heavy loads, but with 100 plus CI engines I don't know that it would be nessessary. I've toted some heavy loads with mine and its just 80 CI. remember this photo ?
I'm definately more of a cruzzer than a racer. Love those bikiny beaches.