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dhillis said:
Also, I offer this as a suggestion for folks with a tachometer. If you commute quite often, if applicable, I challenge you to cruise at 3500RPM whenever possible. After a tank of fuel, compare your MPG's to what you would typically get if not in the neighborhood of 3500 RPM's. My experience has been exceptional fuel mileage at max torque RPM.

Dan
I also love tinkering and respect your endeavor to lower cruising revolutions. I do have to take exception to this statement. I did MANY tanks of gas at 3500 and above. Gas mileage (on a Volusia not a FI C50) did not appreciably fall off till continued cruising at 4300 RPM and above. Then it tanked. So I added an aux tank :?

Jim

Here was the data I was using back then http://www.volusiariders.com/viewtopic.php?t=10293
 

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Discussion Starter #42
vol210, I would say that the reason your bike was efficient up to 4300 is because max torque is started at 3500 on a stock bike. I have not viewed a stock dyno graph, but I would assume based on your experience that the 800's torque curve is sustained through 4300, before it drops off... explaining the worse MPG's. I have viewed a few dyno graphs of modded bikes and appears that the max torque is sustained for approximately 500-1000 RPM's.

Based on those assumptions and using the vulcan speed calculator, max torque is sustained between the speeds of 56-69MPH.

Dan
 

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I find it odd, so many around here ask about a sixth gear, then when someone comes up with a viable option he gets bashed and alot seem downright offended by the fact he wants to try.
Hell, I take some loooong trips on my VOl, and for one would be VERY interested in a higher gear. Keep us updated, look into a producing a kit if you get it to work, and keep tally of the costs please.
From personal expierence, after about 18 hours at 85mph the high revs get a little old. it would be nice to lower them a bit.
 

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dhillis said:
Cyclebiker,

The simple answer to your question is this: an internal combustion engine is most efficient at max torque. Torque is defined as force*distance. An engine is then most efficient at max torque because that is when it can produce the most force in a distance... this is where MPG's come in to play, miles would be considered the distance that the force would have to travel.
Dan
Wrong Dan/dhillis. You are making the mistake of equating Fuel efficiency with engine efficiency. The two do not equate.

If you tuned the C50 engine to produce more torque at the same or higher revs it would be more efficient in producing power as an engine but in no way would it necessarily be more fuel efficient.

For tractability the C50 is purposely tuned for a wide torque band which consequentially reduces the maximum torque of the engine.
 

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I admire this gentleman's out of the box thinking. So many have asked about a sixth gear. So what he wants to undertake this mod. I have heard of a few mods people have done to their bikes that I don't agree with or see the sense of, but in the end IT"S THEIR BIKE to do with as they wish. So leave him alone.
Sir, I would be greatly interested in the results of your endevours. Too bad you are so far away, otherwise I would gladly volunteer to assist you.
 

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Bootlegger said:
Here is a rear differential for a C90, let us know how it turns out.
ebay link
Well if you can get this shipped to you for less than $100, and it makes for the 3:1 ratio you are looking for, and it is a drop in mod with minimal fuss, I'd say it's a no brainer. Your going to lose some power on the bottom end (leaving stops lights and such), but it seems your willing to do that and you just won't know how much effect it has on the lower end till you do it. I think the 2.66:1 would be an absolute dog. the 3.0:1 might not be so bad. (your only talking about moving 600lbs + rider). Definatly worth a try. Good luck.
Viper
 

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lol.. this is a great idea.. gonna book mark this thread to see how it turns out.
 

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alex d said:
is it a just a drop in mod? Is this confirmed?
I should have said IF you can get it for $100 and IF it is a drop in with minimal fuss...............(sorry didn't mean to confuse)
Viper
 

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rear differential

I bookmarked this post and I wanna be the second or third person to volunteer my bike for this endeavor. This would quite possibly be the best mod ever conceived!
 

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472viper said:
alex d said:
is it a just a drop in mod? Is this confirmed?
I should have said IF you can get it for $100 and IF it is a drop in with minimal fuss...............(sorry didn't mean to confuse)
Viper
Thanks, I just about to buy one. I'm hoping it is though, 100 bucks for a rear diff is pretty cheap IMHO :wink:

edit: I was thinking, isn't the wheelbase longer in a c90? So wouldn't the shaft be longer then the c50?
 

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Interesting stuff!

Been reading thru all this, I was wondering what any longterm effects might be by doing this.
 

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Jimco said:
Interesting stuff!

Been reading thru all this, I was wondering what any longterm effects might be by doing this.
Shouldnt realy be any people have been changing gear ratios on cars forever. I would have to say no diferent than having a car with " highway gears "
 

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Here is a rather relevant post I have previously made. I think it should be titled
"HOW TO TURN A HOG INTO A DOG"

Here is an extract from the July 26th Motor Cycle News review of the 2006 HD FLSTF Fat Boy (translated from the English):

“….But the award for the most utterly pointless waste of time has to go to Harley’s inclusion of a sixth gear.
In theory it lowers engine revs at 75mph from 3100rpm to 2800rpm. However, in practice it completely destroys any ability to accelerate. Overtaking on the interstate is as painful as watching a semi doing 61mph crawl past another doing 60mph. To make matters worse it only marginally improves fuel economy.”

Perhaps the above will lend some illumination to the Forum members who don’t yet comprehend that cruisers do not benefit from overgearing or have any need to compete with sport bikes with regard to the number of gears offered.
_________________
 

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CB auctions on ebay is selling a complete brand new take-off C90 final drive assembly for $50. Do a search for Suzuki C90 final drive and it'll show up.
 

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Would the addition of a granny gear improve my towing abilities. I find the rear wheel slips quite a bit on the boat ramp. :shock:

Mod away bro and let me know how it goes!
 

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Yep! and the Buy-it-now is $50. There are 2 of them. You have to search for "C90 final drive"

Even if these are too long it shouldn't be a big deal to cut and re-weld the shaft or sleeve and braze it although it will obviously need the end connections to fit or be easily modified to fit. - on second thoughts it might be easier just to reattach the splines if the shaft needs shortening.

 

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Discussion Starter #59
First off...

CycleBiker, fuel/engine efficiency is relative to what work is being performed. Obviously, if you are doing minimal "work", then you could run the engine at a low RPM and be extremely fuel efficient. However, when you add motorycle/rider weight, cargo load, wind resistant (the biggest issue), etc... you would bog the engine down at a low RPM. Therefore, you try to find where the engine is most fuel efficient in the RPM band, in order to sustain the "work" (in this case traveling down the road). Keeping that in mind, the engine will be most fuel efficient in it's torque band... RPM's below the torque band will bog the motor and you will have to downshift and RPM's above the torque band will be less fuel efficient (as evident when you travel above 70MPH). Also, I've noticed some of your posts are quite antagonistic, which leads me to ask: Are you in or are you out? It seems that you may have some good knowledge and I would love to have your help if possible. However, if you are going to clog this thread with useless opinions, I respectfully ask you to stop responding to this thread.

472viper and alex d, I don't believe the c90 drive is going to be a drop in mod. I spoke with a dealer service tech and had him examine the differences between the c50/c90 and he said the c90's drive housing is considerably larger. Because of time constraints, he was unable to open up the two housing or do any measurements.

Also as far as the c90 is concerned, what happens when the two c90 drive housings are sold on ebay? Then only two bikes get taller gears. I'm looking for a way to please everyone, so that we can all have good cruising bikes. Also, I have decided that I am going to keep with the 3:1 rear end. I believe it will decrease cruising RPM's enough to make it comfortable without bogging the engine down.

I should also make it clear that the point of this project is to lower RPM's for rider comfort, not fuel efficiency, unlike some believe. The lower highway RPM's may increase fuel efficiency, which would be a bonus, but this is NOT the intended purpose. All I want out of this is to cruise on the highway comfortably without having my feet, butt and hands buzzing for an hour when I get off the bike.

Dan
 

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dhillis, I totally agree with you and your efforts. I may be the only Vol rider that normally rides at a max of 75 indicated, if on a freeway I just as soon stay in the right lane and cruise, not that interested in super acceleration from a stop sign, twisties are fun but I find no real desire to seek them out, (too much work and concentration) I don't mind shifting to find the proper gear, gas mileage on my Vol is secondary to reliability. So I really like the idea of a higher rear end gear to make the ride a bit less buzzy. A lot of people keep trying to make their Vol into a Hayabusa, I would be the one to try and make my Vol more like a Bergman.
 
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