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post #1 of 21 (permalink) Old 04-16-2010, 05:33 PM Thread Starter
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MPG Gain?

I've been wondering how to improve highway MPG on our bikes. Not that it's horrible, but we all want that 6th gear at times.

If we can't change the gearing in the bevel drive, could we mod or swap out another bike's final drive/rear wheel for a slight gain there?

Still at work (sorry to those I promised to get back to about parts - it's been a 7am to 7pm week) and just kind of bouncing ideas around at the end of a long week.

Thoughts?

Scheherazade
'86 VN750
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post #2 of 21 (permalink) Old 04-16-2010, 08:08 PM
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On a related topic, did you ride on a 150/90-15 tire before changing out for the 170/80-15 I see in your sigline now?
If so, did you notice any increase in fuel economy when the slightly larger tire was installed?

I have never seen a thread where a final drive for a different motorcycle has been installed on a Vulcan. I would think that each individual motorcycle model that is shaft driven, would have a final drive with specific dimensions to handle the power of that bike. I believe it would be extremely unlikely to find a final drive from one make of mc, that would fit another make of bike of similar size. Similarly the final drive from a Kawi vn750 will not fit the larger vn1500 made by the same manufacturer.

I am not sure what the chances are of being able to swap in a final drive/rear wheel set from another model bike to the vn750. I would guess it is slim to none, without modifications.

It is not like a chain driven bike where you may be able to change a gear for another with one or two more (or less) teeth, to change the gearing and therefore increase or decrease power/speed/fuel economy in varying relationships.

I believe the bigger rear tire you have installed on your vn750 is the only thing you can do to increase your mpg, and that will only make a small difference. Well, you could ride slower I guess, but that was not the answer you were looking for.

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post #3 of 21 (permalink) Old 04-16-2010, 09:24 PM
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I think that I saw someone on here that used a Kawasaki Eliminator back wheel that was a sixteen inch wheel and used the same brake system as well.I may be wrong but I don't think this is my imagination,if it is true you could drop RPM's on the Highway but would lose a little power on the bottom end,same as a gearing change.I just don't know how much difference it would make.




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post #4 of 21 (permalink) Old 04-16-2010, 09:27 PM Thread Starter
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Hey Gordon -

This is mostly about long distance travel for me. My VN can physically cruise all day long at pretty much whatever highway speed I like (and is safe.) However, the range tends to drop as it gulps more fuel. I have daydreams about traveling through the NW and don't want to get stuck in the middle of nowhere.

So I'm generally curious as to ways to extend my range. I.e., more MPG at "travel speed," as opposed to more MPG by driving the bike at 52 on the highway. 52 is decidedly unsafe in many areas around here as traffic can be cutthroat on the freeway.

Fuel economy is a bit better with the 170, in the sense that I can cruise at highway speed at lower RPMs, and thus extend my range. It's maybe a 10% difference? Tops.

So, anyway, it seems if I want better MPG, I can either look into ways of fairing the bike or changing the gearing.

Fairing I'm considering - there's actually not a lot of work out there about true aerodynamic fairings. Most marketed fairings just seem to be about rider protection and/or reducing buffeting on the rider. But that's for another post I think. If there was a way to make our bikes more aerodynamic I might go back to the 150 rear wheel - it'd be quicker to speed than the 170 but (faired) would still be faster than stock because it wouldn't be pushing so much air.

But back to my final drive musings. I know that if you want better MPG on sprocket bikes you can change the rear sprocket to a smaller one. This sacrifices low end torque but allows the engine to rev lower at higher speeds.

So I was just wondering if there was an analogue for our bikes. I know people had talked about adding a sixth gear and how complicated that would be. But what if the final drive/rear wheel was replaced by another shaft driven bikes? That other shaft driven bike might transmit the power from the spinning dive shaft in an entirely different ratio. If there was one, it might be a more fabable swap than messing about with the bevel gear. You'd just have to mate up the new final drive/wheel with the shaft on our bikes.

Anyway, I'm home, my taxes are done, I got good outcomes for my clients today, so I'm going to have a glass of wine and relax.

Scheherazade
'86 VN750
MF Battery, Iridium Plugs, RR relocated, Voltmeter, 170/80/15 Kenda Kruz rear tire, DIY Samsonite hard bags, DIY shaved seat with Beaded seat pad ('cause that's how I roll) and the dreaded STATOR CHANGE.

Shining Black Bess '86 VN750, retired for parts after a fried stator and being knocked (kee-runch) in her parking spot.
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post #5 of 21 (permalink) Old 04-16-2010, 09:36 PM Thread Starter
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BTW - here's a thread at a different forum that has some links to some interesting fairings. http://ecomodder.com/forum/showthrea...ound-7241.html

(PS - I know about the Vetter fairings.)

(PPS - Thanks Denny!)

Scheherazade
'86 VN750
MF Battery, Iridium Plugs, RR relocated, Voltmeter, 170/80/15 Kenda Kruz rear tire, DIY Samsonite hard bags, DIY shaved seat with Beaded seat pad ('cause that's how I roll) and the dreaded STATOR CHANGE.

Shining Black Bess '86 VN750, retired for parts after a fried stator and being knocked (kee-runch) in her parking spot.
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post #6 of 21 (permalink) Old 04-17-2010, 01:13 AM
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What MPG are you getting?????????


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post #7 of 21 (permalink) Old 04-17-2010, 07:07 AM
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For your purpose (extended range) maybe a larger gas tank would be an easier or cheaper fix...???
Just wondering, say a 4.5 gal. tank would give you an extra 50-55 mi. ...
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post #8 of 21 (permalink) Old 04-17-2010, 10:21 AM Thread Starter
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Ron - Oh, 40-45 ish, which isn't bad, but I'd like to get the range up to 200 miles or so. I'm not dying to do so, but it's an idea that I dust off and kick around now and then.

Once in awhile I get something that works and I'm glad to have experimented with. My DIY hardbags for instance: two smallish sampsonite suitcases, a can of black spraypaint, a short length of pipe to cut into spacers, some long bolts (bicycle neck bolts), and voila - waterproof, lockable, and moderately quick detach hard bags.

If I can come up with something to boost me into the 60-70mpg range, that'd be pretty sweet.

Dog- Yeah, that's another good option.

Scheherazade
'86 VN750
MF Battery, Iridium Plugs, RR relocated, Voltmeter, 170/80/15 Kenda Kruz rear tire, DIY Samsonite hard bags, DIY shaved seat with Beaded seat pad ('cause that's how I roll) and the dreaded STATOR CHANGE.

Shining Black Bess '86 VN750, retired for parts after a fried stator and being knocked (kee-runch) in her parking spot.
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post #9 of 21 (permalink) Old 04-17-2010, 11:26 AM
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Run the carbs lean and drop the plug temp range colder X2. Get a good fairing like you already researched (vetter). Bigger gas tank. Slow down on the interstate.

Get a touring bike.

DT

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post #10 of 21 (permalink) Old 04-17-2010, 01:23 PM
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A bigger gas tank is the best suggestion so far. Your bike gets really good gas milage already, other than trading it in for a scooter you aint going to get much better gas mileage out of it.

Small round fairings like the Memphis Shades Hellcat will give you better aerodynamics than a PF3...but cut back on comfort and protection.

As your concept is extended range...not really better fuel ecconomy per se, the bigger tank or "extra" fuel tank is the way to go. There are companies that sell add on fuel tanks that could triple your range.

The 170 tire is wider than the 150 ...but I did not think it was that much taller than the stock. Does anyone have the inflated circumfrence of both tires?

+1 on getting a touring bike.

edit--should point out that even if you could get a 5% gain in fuel mileage (which would be a major increase)..it would mean getting 47mpg instead of 45 mpg.. so you only would be adding 8 miles to your range. Your tiny 2 gallon gas tank IS the limiting issue here.KM

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Last edited by Knifemaker; 04-17-2010 at 01:36 PM.
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