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Discussion Starter #1
Well I've started this post several times and stopped. Gonna roll with it this time. I have several things to discuss about my bike. I'm going to keep this one about fuel and post a separate post on all the rest so I can get legit discussion on one topic and not be confusing. I know there are many people that could care less about gas mileage. I'm not one of them. Since I've been a kid I've kept meticulous information on my vehicles. I keep every fuel fill and the miles and gallons used. This of course gives me MPG. This is one way I tell when something is not right.

So here are some examples of my fuel log.....

(1) 188 miles /3.54 gal =53.1 mpg, (2) 192 miles /3.52 gal=54.5 mpg (3) 190 miles /3.46 gal =54.9 mpg (4) 185 miles /3.55 gal =52.11 mpg

I bought this bike new in '08 and have consistently gotten fuel mileage in the 52-55 mpg range. I made me up a C90 final drive kit and installed it and I get exactly 10mph more on the highway at the same RPM. I have always kept my RPM on 3600 and that put me at an indicated 60 mph dead on the nose. I checked this with my GPS and it is right on....that is to say the GPS showed 53 which is the classic “7 mph” off that the factory speedo is. So now with the C90 drive (2.66 gear) I'm turning exactly 3600 rpm at an indicated 70 mph....As long as I keep that tach reading 3600 or below I get 52-55 mpg. This puts me on my GPS running 63 mph (which is a whole other problem on the freeway....see other thread). I've put several thousand miles on the bike with the C90 drive in and I still get 52-55 mpg....that is until lately.

Now my numbers are these....

(1) 165 miles /3.50 gal =47.1 mpg, (2) 159 miles/3.48 gal =45.68 mpg (3) 161 miles /3.60 gal =44.7 mpg (4) 163 miles /3.7gal =44.0 mpg

That's not normal. You don't just drop 10 mpg average if all else stayed the same. Just for info purposes so you guys wont have to beg for info (I hate when all the info isn't given...lol) here are the things I've done lately since the drop in mileage. Fresh oil change with filter (as always). Fresh air filter. New plugs. Put some Lucas gas treatment in several times with no results. Air in the tires always checked and maintained. The bike is running just fine. Starts very easily. Runs smoothly. I have a little over 30K miles on the bike. And I know a question that will be asked is when was the last time the valves were adjusted. My buddy is a motorcycle tech and his response when I asked him if I needed to adjust my valves was “Is it running bad?” NO “Is it hard to start?” NO “Is it making noises that aren't normal since you've owned it since new?” NO. “Then I would say there's no need.” That's a matter of choice/opinion I know because I lurked on a thread a while ago about when/if you adjust your valves and there seems to be a split opinion. I could care less either way. If it needs it I'll do it...If not then??? Just thought I'd get that out of the way..lol. Exhaust is stock with the “ram some holes all the way thru the mickey plate mod”. Been that way since about a year old. Sounds awesome.

So what do you guys think?
 

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Dont know...

Wind, cold temps, added a windshield, added a passenger. With the Modded drive, the rpms will drop and allow you to roll on more speed with less rpms than stock...even a few more miles per hour will drop the fuel mileage quite a bit. I will say this, when I ride solo, my fuel mileage sucks... when my wife rides as a passenger, I actually get better fuel mileage because I'm more consistent and steady with the throttle.
 

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Well I've started this post several times and stopped. Gonna roll with it this time. I have several things to discuss about my bike. I'm going to keep this one about fuel and post a separate post on all the rest so I can get legit discussion on one topic and not be confusing. I know there are many people that could care less about gas mileage. I'm not one of them. Since I've been a kid I've kept meticulous information on my vehicles. I keep every fuel fill and the miles and gallons used. This of course gives me MPG. This is one way I tell when something is not right.

So here are some examples of my fuel log.....

(1) 188 miles /3.54 gal =53.1 mpg, (2) 192 miles /3.52 gal=54.5 mpg (3) 190 miles /3.46 gal =54.9 mpg (4) 185 miles /3.55 gal =52.11 mpg

I bought this bike new in '08 and have consistently gotten fuel mileage in the 52-55 mpg range. I made me up a C90 final drive kit and installed it and I get exactly 10mph more on the highway at the same RPM. I have always kept my RPM on 3600 and that put me at an indicated 60 mph dead on the nose. I checked this with my GPS and it is right on....that is to say the GPS showed 53 which is the classic “7 mph” off that the factory speedo is. So now with the C90 drive (2.66 gear) I'm turning exactly 3600 rpm at an indicated 70 mph....As long as I keep that tach reading 3600 or below I get 52-55 mpg. This puts me on my GPS running 63 mph (which is a whole other problem on the freeway....see other thread). I've put several thousand miles on the bike with the C90 drive in and I still get 52-55 mpg....that is until lately.

Now my numbers are these....

(1) 165 miles /3.50 gal =47.1 mpg, (2) 159 miles/3.48 gal =45.68 mpg (3) 161 miles /3.60 gal =44.7 mpg (4) 163 miles /3.7gal =44.0 mpg

That's not normal. You don't just drop 10 mpg average if all else stayed the same. Just for info purposes so you guys wont have to beg for info (I hate when all the info isn't given...lol) here are the things I've done lately since the drop in mileage. Fresh oil change with filter (as always). Fresh air filter. New plugs. Put some Lucas gas treatment in several times with no results. Air in the tires always checked and maintained. The bike is running just fine. Starts very easily. Runs smoothly. I have a little over 30K miles on the bike. And I know a question that will be asked is when was the last time the valves were adjusted. My buddy is a motorcycle tech and his response when I asked him if I needed to adjust my valves was “Is it running bad?” NO “Is it hard to start?” NO “Is it making noises that aren't normal since you've owned it since new?” NO. “Then I would say there's no need.” That's a matter of choice/opinion I know because I lurked on a thread a while ago about when/if you adjust your valves and there seems to be a split opinion. I could care less either way. If it needs it I'll do it...If not then??? Just thought I'd get that out of the way..lol. Exhaust is stock with the “ram some holes all the way thru the mickey plate mod”. Been that way since about a year old. Sounds awesome.

So what do you guys think?
To kick start my thinking on this, I looked in the Clymer manual for ''poor fuel economy'' or ''excessive fuel consumption'' - no such heading.... :shades:

So with that perspective.... There are so many factors in fuel mileage.

  • The road surface/terrain is a factor
  • The wind - cross/tail/side direction and speed.
  • Your lead foot.... with familiarity of your bike comes a more aggressive riding style... imperceptible perhaps, but it is there.
  • Windshield angle changed?
  • have you put chaps on your engine bars?
  • Are you carrying more gear/weight?
  • Are the brakes dragging?
  • Is the ignition timing still correct..... It is not adjustable but set by the ECM with inputs from several sensors....
  • Air cleaner condition - you've already changed that....
  • Clutch slippage..... no mention of a problem there and you would have noticed it if there was.
  • The DJ drive factor... I know it's been said that this should allow an increase in fuel mileage but operating familiarity may allow the rider to tend to lug the engine which can affect fuel economy.
  • the operation of the Secondary Throttle Valve... is it moving freely and appropriately for operating conditions?
  • Is the Throttle position sensor still adjusted correctly... That tells the ECM how much fuel to inject. Can be checked and adjusted using the Suzuki diagnostic connector and the readout on your odometer display.
  • Engine coolant temperature affects the enrichment mode of the ECM... if it is sensing a cooler engine temp... not a high likelihood but if the other possible causes are eliminated....
  • Valve adjustment.... incorrect/unequal/ valve clearances affect power in an almost imperceptible way causing the rider to add to throttle position and that degrades fuel economy...... do not discount this as a ''contributing factor'' even though it may not be the only cause of the complaint.
  • There are probably a few more factors as well..... some you have covered in your post above.
Way back when - we had to document fuel consumption complaints for the Ford dealership where I worked. We had a calibrated fuel container system that was plumbed into the fuel system and run on a section of road that was selected for that specific purpose. The test was a two way run over the same stretch of road to account for the slope of the road and any wind factors at a specific speed.

There is no way to account for all the changeable factors that affect fuel economy from one tank to another. all you can do is make sure that the mechanical systems and electronic controls are set and operating as they were designed.
 

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Discussion Starter #5
Just to address a couple of the more simple questions.....nothing has changed since the mileage dropped off. Don't have an engine guard so no chaps. Windshield not changed. No more weight. No added passenger as I have shaved the rear fender of seat etc. I was getting my normal mileage running indicated 70 @ 3600 for the longest time. Weird it just seemend to happen all of a sudden because I log my mileage every tank. It didn't just drop a couple mpg over a month or two. The DJ type drive got me identical gas mileage for several thousand miles before wammo. All the more technical stuff I'd obviously have to check. I don't know... :( Thanks for the very excellent posts! keep them coming if there's anything else.
 

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Discussion Starter #6
Are you buying your gas all in the same place?
Lol....Im never in the same place that often I don't think. But for the first 6 years i got 52-55 mpg and I bought gas all over the place. Even moved a couple times. Good comment though...never thought about that. :)
 

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What was the approximate date that you first noticed the drop in mileage?

Have you had and ''peaks'' in mileage where it increased for 1 or 2 tanks?

Do you log the location of your fuel ups now?
 

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Discussion Starter #8
What was the approximate date that you first noticed the drop in mileage?

Have you had and ''peaks'' in mileage where it increased for 1 or 2 tanks?

Do you log the location of your fuel ups now?
Mileage dropped in February. It was cold here in Dec and Jan and it was still cold in Feb....Never had 10 mpg increases...Never been over 55 mpg as a matter of fact. I mean its always been mega consistent. Maybe I should start logging location huh? I'm just wondering IF the valves actually do need adjusting badly. Although that would have happened gradually and not just "one day in Feb"....lol. Good thoughts! Thanks!
 

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I have experienced similar for no apparent reason, tried everything from adjust my GMan to removing my saddlebags. Purely by accident I discovered my issue, I filled up with the high octane premium at a Caltex instead of a the same at my regular BP and my milage returned. I've since experimented and there is a marked difference between the two brands.

In fact we did a big charity ride a couple of weekends ago and could only get BP, at 240klms I was looking for a servo, I used to be able to consistently get 280-300klms out of a tank on a long run.

I don't keep records on the bike but I do know when I'm about to run out of fuel when I should still have a good 50klms to go.
 

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I have almost 30 K on my bike and had to adjust valves twice.
I'm sure you know Suzuki now recommends you do it every 12 K miles, so adjust them and eliminate that potential cause.
 

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Gas companies change formulas based on the season. That will change things. Carbon build up on your piston?
 

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Gas would be my guess too, but if it means anything to you, my bike has been consistently in the 40 to 45 range since I got her. Mine is an '06 though, so maybe it is just age. On to of that, I have V&H pipes a windshield, sale bags, and a fat arse rider with a lead wrist. Basically everything that will ruin your fuel economy! :scoot:

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Discussion Starter #13
Yeah I'm sure gas could make a difference. Thing is....I can't argue with the fact that I've spent the last almost 6 years buying every conceivable brand of gas and it's never varied one bit. I can't see it magically starting now. Basically no variable like bags, weight, wind, tires, etc have changed AT ALL in a long time....way before any change in mileage. Something way different than an external variable has changed. Proly never find it...lol. I don't feel like I will anyway. You don't just go from 54mpg to 44mpg in a week.

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Seems to me it could be the cold weather. Have you been letting the bike warm up longer before taking off? If the bike adjusts to the weather, there could be a difference in the air/gas ratio. I noticed mine runs a little different when I ride at 35 degrees vs 75 degrees. Warm up takes longer and smells richer in the cold weather.
 

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Well I've started this post several times and stopped. Gonna roll with it this time. I have several things to discuss about my bike. I'm going to keep this one about fuel and post a separate post on all the rest so I can get legit discussion on one topic and not be confusing. I know there are many people that could care less about gas mileage. I'm not one of them. Since I've been a kid I've kept meticulous information on my vehicles. I keep every fuel fill and the miles and gallons used. This of course gives me MPG. This is one way I tell when something is not right.

So here are some examples of my fuel log.....

(1) 188 miles /3.54 gal =53.1 mpg, (2) 192 miles /3.52 gal=54.5 mpg (3) 190 miles /3.46 gal =54.9 mpg (4) 185 miles /3.55 gal =52.11 mpg

I bought this bike new in '08 and have consistently gotten fuel mileage in the 52-55 mpg range. I made me up a C90 final drive kit and installed it and I get exactly 10mph more on the highway at the same RPM. I have always kept my RPM on 3600 and that put me at an indicated 60 mph dead on the nose. I checked this with my GPS and it is right on....that is to say the GPS showed 53 which is the classic “7 mph” off that the factory speedo is. So now with the C90 drive (2.66 gear) I'm turning exactly 3600 rpm at an indicated 70 mph....As long as I keep that tach reading 3600 or below I get 52-55 mpg. This puts me on my GPS running 63 mph (which is a whole other problem on the freeway....see other thread). I've put several thousand miles on the bike with the C90 drive in and I still get 52-55 mpg....that is until lately.

Now my numbers are these....

(1) 165 miles /3.50 gal =47.1 mpg, (2) 159 miles/3.48 gal =45.68 mpg (3) 161 miles /3.60 gal =44.7 mpg (4) 163 miles /3.7gal =44.0 mpg

That's not normal. You don't just drop 10 mpg average if all else stayed the same. Just for info purposes so you guys wont have to beg for info (I hate when all the info isn't given...lol) here are the things I've done lately since the drop in mileage. Fresh oil change with filter (as always). Fresh air filter. New plugs. Put some Lucas gas treatment in several times with no results. Air in the tires always checked and maintained. The bike is running just fine. Starts very easily. Runs smoothly. I have a little over 30K miles on the bike. And I know a question that will be asked is when was the last time the valves were adjusted. My buddy is a motorcycle tech and his response when I asked him if I needed to adjust my valves was “Is it running bad?” NO “Is it hard to start?” NO “Is it making noises that aren't normal since you've owned it since new?” NO. “Then I would say there's no need.” That's a matter of choice/opinion I know because I lurked on a thread a while ago about when/if you adjust your valves and there seems to be a split opinion. I could care less either way. If it needs it I'll do it...If not then??? Just thought I'd get that out of the way..lol. Exhaust is stock with the “ram some holes all the way thru the mickey plate mod”. Been that way since about a year old. Sounds awesome.

So what do you guys think?
First, engines wear as you use them. There is nothing you can do to prevent it. Some of the wear translates into friction losses which will show up as variances in your MPG. With the addition of carbon build-up in the piston and other wear-related factors, you no longer have a sparkling clean engine. YMMV. What else can affect the mileage? Air temp. Humidity. Barometric pressure. Quality of the fuel. But there is one glaring problem that I see.....

Now you have 30k on your engine and have never touched your valves?????? That right there is a huge red flag, especially since the manual spells out a valve check/adjustment every 7500 miles..... Are your valves probably tight? Is the pope Catholic? Would you see a return of some of your lost performance? Almost certainly.

Crack the engine, adjust the valves, then go back to riding with a smile on your face.
 

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Discussion Starter #16
Seems to me it could be the cold weather. Have you been letting the bike warm up longer before taking off? If the bike adjusts to the weather, there could be a difference in the air/gas ratio. I noticed mine runs a little different when I ride at 35 degrees vs 75 degrees. Warm up takes longer and smells richer in the cold weather.
lol....i live in Alabama. We are already in spring pollen season. It was almost 80 here yesterday. Proly be 100 in a week :(
 

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I have almost 30 K on my bike and had to adjust valves twice.
I'm sure you know Suzuki now recommends you do it every 12 K miles, so adjust them and eliminate that potential cause.
Not trying to hi-jack this thread but I just talked to my Suzuki dealer and he confirmed valve adjustment intervals are 7600 miles.
I called and asked because I thought they changed it to 16,000 miles and was corrected by Skrapiron. Turns out 16,000 is for the V-Star 1300.
 

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Discussion Starter #18
Not trying to hi-jack this thread but I just talked to my Suzuki dealer and he confirmed valve adjustment intervals are 7600 miles.
I called and asked because I thought they changed it to 16,000 miles and was corrected by Skrapiron. Turns out 16,000 is for the V-Star 1300.
You are correct. I don't disagree with when Suzuki says to adjust them. I just trust my friend who has been a certified motocycle tech (works at the Suzuki dealer in the next town over) more than I trust a dealer. Kinda not much difference EXCEPT for the fact he isn't trying to up sale me or rip me off. He's a friend and just gave me the advice above that I mentioned. See above where i said this.....

And I know a question that will be asked is when was the last time the valves were adjusted. My buddy is a motorcycle tech and his response when I asked him if I needed to adjust my valves was “Is it running bad?” NO “Is it hard to start?” NO “Is it making noises that aren't normal since you've owned it since new?” NO. “Then I would say there's no need.”

Guess like Scrap said just do it....lol.
 

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lol....i live in Alabama. We are already in spring pollen season. It was almost 80 here yesterday. Proly be 100 in a week :(
Thought you said you had a colder winter than normal in your part of the world. If it is colder than you have seen in the last several years, stands to reason the bike would be a little different.

Mileage dropped in February. It was cold here in Dec and Jan and it was still cold in Feb....
You likely have a combination of several little things working together.
 
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