Gear mod for better mpg?

[JvM2003]

Here’s the deal, I now commute 120 miles roundtrip to work each day, Lancaster to Burbank & back (all highway) I average 80mph + (85 on my speedo = 6,500 rpm) I’m in 6th gear the entire ride.

I talked to a friend & he said I could mod my 6th gear so it’s more of an “overdrive” gear. It would reduce the rpm’s & maintain the same speed, so I’d get better gas mileage (under the theory “lower rpm’s = less gas burned”)

I know I could replace the sprocket with a smaller one, but that would change the torque of all my gears (& I only want to change my 6th gear) & I’m guessing it’s not possible to add a 7th gear.

Anyway, I figure if I can mod it so instead of being at 6,500rpm at 85mph, it’s around 4,000rpm at 85mph, I’d get a lot better mileage.

Any ideas?

Thanks,

J.

[soulofadra6o]

that sounds like a good idea..but wont adding another gear over complicate things and maybe cause problems later on down the line?

[kc1717]

you can change the internal 6th gear,....for the ammout of time, money and hastle it would take you to do it,...its far cheaper to just deal with what you have.

[Ikazuchi]

adding another gear would be damn near impossible.... changing out your current 6th is difficult...but a good solution.

If your buddy can do the change for under $200, I'd say go for it and let us know how it works out.

Otherwise I'd say just drop two teeth off your rear sprocket and deal with the slight lag in lower gears.

[Manx]

Slow down. Adding five minutes each way could save you some dough - riding at 80mph isn't nearly as efficient as riding at 70mph. ;)

[Jethro]

J,

What kind of mileage are you getting?

I used to get 200 miles before the fuel light would light up on my '01 SV650S with stock gearing (that's 62mpg). That included lane-splitting from Tustin to Marina Del Ray and back every day.

Slowing down like Manx says will help a lot. Smooth operation of the throttle will help as well. Fast acceleration costs money.

Luck,

J~

[soulofadra6o]

yes you'd be suprised how much not rocketing out of stop lights will save you in gas

[racinteach]

I have to agree...wiht all the great minds above just droping your speed down a bit will save quite a bit... as for lower RPMS saving gas...they say a car that idles in traffic will be less efficient and get worse gas millage then one traveling at 55 ...I would say it may be the same for bikes...try it and see before you drop the big bucks...

[Peiell]

Originally posted by Jethro

I used to get 200 miles before the fuel light would light up on my '01 SV650S with stock gearing (that's 62mpg). That included lane-splitting from Tustin to Marina Del Ray and back every day.
J~

Daaaamn, Jethro. 62 mpg? And I thought I was doing well with 50-51 on my 04 nakkid. I know the S has one less back tooth, but... damn. What's your cruising speed for that mileage?

[blong]

just go up a tooth up front.
$30 and it'll drop your 6th gear rpms.

[Manx]

Originally posted by blong
just go up a tooth up front.
$30 and it'll drop your 6th gear rpms.

And for all the other gears. This is a great option if that bike is only a commuter, but it could take the fun out of any "aggressive" riding.

[blong]

Originally posted by Manx
And for all the other gears. This is a great option if that bike is only a commuter, but it could take the fun out of any "aggressive" riding.

Just buy another SV. That's what I did anyway.

[smokescreen]

you do not want to drop to 4k rpms. There is no power ther. 5k is a very efficient rpm for this motor.

Also, the gen 1's get worse gas mileage in town, and better on the freeway.

It's because around town, they are enriched with throttle twist, whereas on the freeway, at constant throttle, they run lean.

The gen 2 is fuel injected, so it's always metered.

My wife's 900 gets much better freeway mileage than my SV... But then, I weigh 200lbs, don't I, and she AND her bike, weigh just slightly more than my bike does wet, sans rider.

[Jethro]

Peiell,

That was during some study on smooth throttle control. I forget which book it was in. Probably "Sport Riding Techniques".

The sprockets were new, the chain was also new and kept well-lubed. Tire pressures were kept a bit higher than usual just for commuting. The throttle was never turned to full during the test. I never tried to out-run the cars on the on-ramps.

Not sure about average speed, but there were about 30 miles of lane-splitting during an 80 mile commute. Never really took it over 75 except on the 405 north to the 105 west ramp. That's a fun transition!

I also found that chain, sprocket, rear-tire, and brake-pad wear all fell dramatically during that period.

The fact that I weigh less than 130 pounds in full gear and don't stick up much behind the fairing helped a lot.

Out of curiosity, I ran a spreadsheet on riding-costs at that time. Everything included, it was costing just over $0.11 a mile to run that bike.

Ride safe,

J~

[Manx]

Originally posted by Jethro
Peiell,

That was during some study on smooth throttle control. I forget which book it was in. Probably "Sport Riding Techniques".

The sprockets were new, the chain was also new and kept well-lubed. Tire pressures were kept a bit higher than usual just for commuting. The throttle was never turned to full during the test. I never tried to out-run the cars on the on-ramps.

Not sure about average speed, but there were about 30 miles of lane-splitting during an 80 mile commute. Never really took it over 75 except on the 405 north to the 105 west ramp. That's a fun transition!

I also found that chain, sprocket, rear-tire, and brake-pad wear all fell dramatically during that period.

The fact that I weigh less than 130 pounds in full gear and don't stick up much behind the fairing helped a lot.

Out of curiosity, I ran a spreadsheet on riding-costs at that time. Everything included, it was costing just over $0.11 a mile to run that bike.

Ride safe,

J~

=D>

Nice - that's the kind of experimentation I like to hear about. People are amazed that my 1k gets ~50mpg when I slab it (~40mpg in the twisties) and I tell them it's because I try to be smooth on the throttle and just cruise at about 75mph in 6th. Higher tire pressures also help when commuting, but people need to remember to drop the pressures a bit when the riding turns aggressive. Rabbitting around town just kills my mileage...

[Rocko]

Originally posted by Manx
And for all the other gears. This is a great option if that bike is only a commuter, but it could take the fun out of any "aggressive" riding.

From my experience changing the gearing doesn't really make any real difference in acceleration.

I switched from a 45 tooth to a 47 tooth sprocket on the rear because when I rode someone's bike that had 47 teeth, the seat of the pants meter went, "Holy chit!!!! this thing accelerates like a rocket!"

After riding my bike with the new gearing, I tried riding an SVS with 44 teeth on the rear. Compared to my bike with 47, the SVS felt much less torquey.

However, when "racing" on the track side by side with the SVS, I was not able to pull away from it on the main straights, the acceleration of the two bikes seemed pretty evenly matched. Same with my bike against a naked with a 45 tooth rear sprocket. Also, the two other riders ride at pretty much the same pace I do, so I don't think corner exit speed was a factor.

So yeah, if you love doing power wheelies then you might be bummed about going down a tooth or two, but in reality, i don't think it's going to slow you down at all.

[Manx]

Thanks for sharing your real-world experience - you have added a good perspective. I just want him to keep in mind that +1 in front is equal to -3 in the back (and vice-versa) - he will give up low-end acceleration to achieve higher top speed at lower RPMs.

The easiest, cheapest way to save fuel is still my first suggestion: slow down. ;)

[athflying79]

I changed my gearing 1 down and 1 up and it made quite a difference. My mileage suffered also. I like the acceleration though so I don't regret it.

[No_Brakes23]

Originally posted by Manx
Slow down. Adding five minutes each way could save you some dough - riding at 80mph isn't nearly as efficient as riding at 70mph. ;)

My bike "parks" well at 80mph, not as well as it did when it was stock, (The torque dip acted like a mild cruise control.)

Oh and I fall asleep at 70mph.

Personally, I get 40mpg even if i ride like a prick, 45-50 if I take it easy or keep it mostly on the highway.

This bike could totally use a 7th gear though, I am always trying to shift up into it.

Originally posted by Manx
The easiest, cheapest way to save fuel is still my first suggestion: slow down. ;) That is probably true, but time is money, and I'll pay for the gas.

Since getting my last ticket in my cage I dropped it from 85-90 to 70-75, (Thank god for cruise control in cars,) and I notice an increase in my travel times. I also get a lot more drowsy at the lower speed.

[Manx]

I was trying to help JvM2003 squeak his dollars as far as they'll go- that was his question. My advice obviously doesn't apply to you, since going fast is more important to you than maximizing MPG.

You might want to have someone check out your narcolepsy issue... ;)

[No_Brakes23]

Originally posted by Manx
I was trying to help JvM2003 squeak his dollars as far as they'll go- that was his question. My advice obviously doesn't apply to you, since going fast is more important to you than maximizing MPG.

You might want to have someone check out your narcolepsy issue... ;)

You're right, I took your advice out of context.

And yeah, keeping it around 70 would prolly help loads.

Sprockets aren't cheap, either.

[Zak650]

Hi,

I've run 17:45 gearing for about 20 or 30,000 miles it does improve gas milage and places 5th gear where 6th would be normaly so as ffar as rpms go it does give you that extra gear. The things that make milage are areodynamics, gearing, engine tune, and driving technique. The biggest problem getting extremely high gas milage out of an SV is keeping yourself from having fun when driving one. It's just very difficult to not just blast about and drive sedately.

Zak

Rifle Fairing Yamaha 175 exciter, hwy 1, 45 mph average speed Carmel to Big Sur and back - milage 392 mpg

[Suprachrgd82]

Drop 1-5 teeth out back or add one up front if you wanna mess with gearing.

You'll have to slip the clutch a little more to get rolling and the bike won't pull as hard on throttle.

It will drop the RPMs in 6th and slightly improve efficiency.



Poor high speed MPGs are a result of drag and frictional loss.

Use a good quality oil in the engine, 15wt or thinner. This will slightly shorten engine life, but increase fuel efficiency.

Keep your chain tensioned and lubed.

Tuck at speeds above 65. Wind resistance accounts for a lot of drag. By tucking, you won't have to twist the throttle as much to maintain 80 MPH.