fuel milage increased?
09-05-2011 | 12:00 PM
#1
Thread Starter
99 superhawk
Superstock
Joined: Jun 2011
Posts: 256
From: jasper Ga.
fuel milage increased?
well I am happy with this it still begs me to wonder why lol. I haven't changed my driving habbits, the only things different in this tank from other tanks I can come up with is (could it be) I filled the tank with regular unleaded instead of super (due to they were out of super at the time).Oh and of course my rear tire is wore down lol. I was getting only 80 miles out of a tank before fuel light, and that was consistant. now I got all of a sudden 105 miles out of this tank before light came on? wierd. anyone else had this happen at a random?
09-05-2011 | 03:03 PM
#3
Administrator
World Champion
Joined: Dec 2004
Posts: 105,287
From: Fulton, MO
Curious, why would you lean out high octane? I could understand advancing timing, but according to everything I've ever learned, jetting should remain the same no matter what octane you use. Ethanol content, yes, jetting could be required because ethanol has significantly different btu/lb than gasoline.
09-05-2011 | 03:54 PM
#4
Senior Member
SuperBike
Joined: Mar 2007
Posts: 1,611
From: Belgium, WI
seeing as we are not running at stoich, almost ever... Higher octane fuel will resist detonation, or ignition itself, better...leading to the ability to utilize the best a/f ratio. Keeping all things the same, its resistance to burning decreases fuel. In other words, if you have the bike perfectly jetted for 87, going to 89, 91, 93, 100, 110, and beyond will just decrease power if no jetting occurs because temperatures in the cylinder will drop because less and less fuel will be burned, which will decrease power.
06-21-2012 | 12:29 AM
#5
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SuperBike
Joined: Jan 2007
Posts: 2,168
Bill,
You know my VTR and I think I told you I recently swapped my carbs again (I have 2 sets for this purpose), which I do every 2 or 3 years. As usual, I cleaned the "new" set (which were pretty clean since I use Chevron Techron concentrate plus) and jetted the front up to 180 (it was 178F/180R) and reused the same OE needles shimmed .040", OE air filter, longer [rear] velocity stack also on the front carb and 2bros slip-ons. I also turned out the front fuel screw to 2.5 to match the rear and syncronized using a Twin Max (double-checked with a mercury manometer to with 3 mm +/- at all revs). The reason for this was I kept seeing what appeared to be micro ***** of aluminum on the plugs caused IMO by detonation; more so on the front plug (which is weird because it should run cooler). Very concerned given my 3-97 baby has almost 75k miles and knowing the crap they label gasoline with 10% ethanol in NE Illinois (and insult to injury with the highest prices in the country) keeps getting worse, I decided to try running mid-grade. After about 1,000 miles now and having checked periodically with three sets of fresh plugs, surprise, surprise, surprise, they look about perfect (as well as can be determined with ethanol laced gas) and no more micro-*****. I also runs much better and idles consistently smoother (I keep the idle a bit higher at 1400 rpm), picks up faster and almost seems like it has a fresh engine; pulling harder than I can remember. And while I know we have a relatively low compression and the "facts" about the need or lack thereof for anything other than regular, plus I hate paying even more per gallon, my mileage has actually increased from 31 ~ 34 mpg to 35 ~ 40 mpg! And this is in 90+ degree ambient temperatures!!!
Now explain that! I shudder to think what it might do running premium...
You know my VTR and I think I told you I recently swapped my carbs again (I have 2 sets for this purpose), which I do every 2 or 3 years. As usual, I cleaned the "new" set (which were pretty clean since I use Chevron Techron concentrate plus) and jetted the front up to 180 (it was 178F/180R) and reused the same OE needles shimmed .040", OE air filter, longer [rear] velocity stack also on the front carb and 2bros slip-ons. I also turned out the front fuel screw to 2.5 to match the rear and syncronized using a Twin Max (double-checked with a mercury manometer to with 3 mm +/- at all revs). The reason for this was I kept seeing what appeared to be micro ***** of aluminum on the plugs caused IMO by detonation; more so on the front plug (which is weird because it should run cooler). Very concerned given my 3-97 baby has almost 75k miles and knowing the crap they label gasoline with 10% ethanol in NE Illinois (and insult to injury with the highest prices in the country) keeps getting worse, I decided to try running mid-grade. After about 1,000 miles now and having checked periodically with three sets of fresh plugs, surprise, surprise, surprise, they look about perfect (as well as can be determined with ethanol laced gas) and no more micro-*****. I also runs much better and idles consistently smoother (I keep the idle a bit higher at 1400 rpm), picks up faster and almost seems like it has a fresh engine; pulling harder than I can remember. And while I know we have a relatively low compression and the "facts" about the need or lack thereof for anything other than regular, plus I hate paying even more per gallon, my mileage has actually increased from 31 ~ 34 mpg to 35 ~ 40 mpg! And this is in 90+ degree ambient temperatures!!!
Now explain that! I shudder to think what it might do running premium...
Last edited by skokievtr; 06-21-2012 at 12:39 AM.
06-21-2012 | 10:43 AM
#6
Seasoned tech
SuperSport
Joined: Apr 2012
Posts: 576
From: Issaquah, WA
Most any pump fuel grades you're not going to need, nor see any difference in jetting from regular to premium. They are pretty much all the same junk with a little more additive in them to raise the octane and prevent detonation. It's when you get into race fuels you'll start seeing the difference in fuel quality that will necessitate the different jetting. Race fuels are a denser fuel without all the additives they put in the pump gas to try to sell you on their brand (such as the Chevron with Techron).
Running higher octane fuel than what you need will do nothing for you and can actually hurt your power, as described above, the resistance to combustion will start to just flat out not burn as well and make less power unless you've got enough compression to raise the cylinder temps a bit higher and make the fuel burn better.
As for your mileage incrase running to rich or to lean will cause poor fuel economy. It sounds like with the new carb swap and other mods/jetting it's just made your bike more efficient. Sounds like you were running a touch lean on the front cylinder before and now it's dialed in about right.
Running higher octane fuel than what you need will do nothing for you and can actually hurt your power, as described above, the resistance to combustion will start to just flat out not burn as well and make less power unless you've got enough compression to raise the cylinder temps a bit higher and make the fuel burn better.
As for your mileage incrase running to rich or to lean will cause poor fuel economy. It sounds like with the new carb swap and other mods/jetting it's just made your bike more efficient. Sounds like you were running a touch lean on the front cylinder before and now it's dialed in about right.
06-21-2012 | 12:13 PM
#7
Senior Member
SuperBike
Joined: Jan 2007
Posts: 2,168
Reread my post more carefully. The only change I made was going up from a 178 to a 180 in the front and 1/4 turn out on the pilot screw. I made no other changes and none to the rear. I also have run richer to no better effect. One jet size and a fraction enriching in the idle-1/4 throttle circuit would not account for elimination of detonation and better gas mileage. I also only use 1 ounce of Techron Con+ per gallon about every 7 to 10 tank fill-ups. I know engines and tuning. I have a university degree that includes power systems (hands-on not just text book) and worked in the aerospace industry which included reciprocating piston, rotary (Wankel), turbofan jet, and liquid & solid fuel rocket engines. My old department section provided research data to Keith Owen for his and Trevor Coley's book entitled " Automotive Fuels Handbook" (published by the SAE). I also personally have been wrenching on motorcycle, light aircraft, drag race car and ultralight engines since the mid 1970's. I remember when gasoline was gasoline and cost 25 cents per gallon.
06-21-2012 | 12:39 PM
#8
Seasoned tech
SuperSport
Joined: Apr 2012
Posts: 576
From: Issaquah, WA
Yeah was just saying that with the mods you'd done previously it sounds like it was running lean(the tiny aluminum ***** on your piston would be another indication of this) and by richening it up it's made it run more efficiently.
What I don't quite understand is why you pose such a question then when you get an answer you fire back with all your experience that one would have to assume you should know the answer to your question with the experience you have.
Another simple solution is summer blend fuels. In some areas they increase ethanol I belive it is, for winter fuels which seems to make for worse fuel mileage. Could be with this last fill up that you've got some summer blend fuel.
What I don't quite understand is why you pose such a question then when you get an answer you fire back with all your experience that one would have to assume you should know the answer to your question with the experience you have.
Another simple solution is summer blend fuels. In some areas they increase ethanol I belive it is, for winter fuels which seems to make for worse fuel mileage. Could be with this last fill up that you've got some summer blend fuel.
06-21-2012 | 06:16 PM
#9
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SuperBike
Joined: Jan 2007
Posts: 2,168
Yeah was just saying that with the mods you'd done previously it sounds like it was running lean(the tiny aluminum ***** on your piston would be another indication of this) and by richening it up it's made it run more efficiently.
What I don't quite understand is why you pose such a question then when you get an answer you fire back with all your experience that one would have to assume you should know the answer to your question with the experience you have.
Another simple solution is summer blend fuels. In some areas they increase ethanol I belive it is, for winter fuels which seems to make for worse fuel mileage. Could be with this last fill up that you've got some summer blend fuel.
What I don't quite understand is why you pose such a question then when you get an answer you fire back with all your experience that one would have to assume you should know the answer to your question with the experience you have.
Another simple solution is summer blend fuels. In some areas they increase ethanol I belive it is, for winter fuels which seems to make for worse fuel mileage. Could be with this last fill up that you've got some summer blend fuel.
As to summer and winter blends, yes winter blends do seem to create more issues but since around here we don't run much after November and before May, the winter gas is only brief inconvenience. However, it is my understanding that ethanol content can be no higher summer or winter, and that it is the other (oxygenating) additives that are varied by season to compensate for lower or higher temperatures to promote optimal atomization to meet emission regulations. Unfortunately, the baseline engine parameters for which these fuels are targeted do not meet the needs of many motorcycles, or at least those without sophisticated ignition controls and/or fuel injection.
Finally and as I stated previously, after 1,000 miles I have determined that the mid-grade E10 gasoline available here in the Chicagoland and southeast Wisconsin minimally has "cured" the detonation. So while relative to some other under-stressed motorcycle engines the VTR gets abysmal gas mileage, 1,000 miles equates to significantly more than one tankful of fuel. Furthermore, summer grade gas did not come online here until about a month ago, which was after I started running mid-grade.
06-21-2012 | 08:47 PM
#10
Senior Member
SuperBike
Joined: Mar 2007
Posts: 1,611
From: Belgium, WI
You want an explanation for your fuel consumption change with 3 variable changes and only one somewhat scientific measurement? Yeah, can't explain that much. I can tell you that my Super Tenere gets 5mpg better with non ethanol. Maybe there is some connection between what I experience as better fuel mileage and you experience a benefit from a higher octane. this is merely speculation...
06-21-2012 | 10:15 PM
#11
Member
Squid
Joined: Sep 2011
Posts: 48
Could be, with the jetting change, you now have much better balance between the two cylinders. Especially on a twin this can have a noticeable effect on mileage and smoothness of running.
When I changed my needles shims from having a .010" difference front to rear to having a .020" difference front to rear, I picked up 3-4 MPG and the engine ran noticeably smoother. I was pleasantly surprised, didn't think .010" could make that big of a difference.
Sometimes you get lucky with trying different setups trial and error. Best way to get the jetting and balance right is with a couple of wideband O2 controllers that you can datalog with.
When I changed my needles shims from having a .010" difference front to rear to having a .020" difference front to rear, I picked up 3-4 MPG and the engine ran noticeably smoother. I was pleasantly surprised, didn't think .010" could make that big of a difference.
Sometimes you get lucky with trying different setups trial and error. Best way to get the jetting and balance right is with a couple of wideband O2 controllers that you can datalog with.
06-22-2012 | 10:34 AM
#12
Seasoned tech
SuperSport
Joined: Apr 2012
Posts: 576
From: Issaquah, WA
Skokievtr I must appologize, my comment about why you posted was a little off. For some reason when I posted about it being interesting that you posed such a questions when you were apparently overqualified to answer it I had it my head that you were the original poster. Going back and re-reading I see I was a bit off in my post. I appologize for that.
As for the deterioration in performance/lean detonation issues over the last couple of years it could also just be that the fuel quality has gone down hill overall.
I'm not sure about the entanol changing from summer to winter blends, I just know they use more oxygenation as you said and I was thinking off the top of my head it was from the ethanol. It could be from other additives though.
As for the deterioration in performance/lean detonation issues over the last couple of years it could also just be that the fuel quality has gone down hill overall.
I'm not sure about the entanol changing from summer to winter blends, I just know they use more oxygenation as you said and I was thinking off the top of my head it was from the ethanol. It could be from other additives though.
06-22-2012 | 01:00 PM
#13
Senior Member
SuperBike
Joined: Jan 2007
Posts: 2,168
You want an explanation for your fuel consumption change with 3 variable changes and only one somewhat scientific measurement? Yeah, can't explain that much. I can tell you that my Super Tenere gets 5mpg better with non ethanol. Maybe there is some connection between what I experience as better fuel mileage and you experience a benefit from a higher octane. this is merely speculation...
And you cheeseheads are lucky you can even find ethanol-free gas, as there 0 in NE IL and very few downstate. WI has tons more. I'm sure you've been to this website Ethanol-free gas stations in WI
Could be, with the jetting change, you now have much better balance between the two cylinders. Especially on a twin this can have a noticeable effect on mileage and smoothness of running.
Balance? Individual carburation or variances in jetting between cylinders (which below you stated you increased rather than equalized) is not what effects the smoothness. Synchronizing the opening of the butterfly valves while achieving the highest idle via the fuel screws is what smooths out or "balances" the carbs to each other. Fuel delivery as controlled from idle to FWO by 4 circuits (5 if you include the start enrichener) have the greatest effect on mileage although a well fed, clean running engine is more efficient and thus should produce the best mileage.
When I changed my needles shims from having a .010" difference front to rear to having a .020" difference front to rear, I picked up 3-4 MPG and the engine ran noticeably smoother. I was pleasantly surprised, didn't think .010" could make that big of a difference.
Sometimes you get lucky with trying different setups trial and error. Best way to get the jetting and balance right is with a couple of wideband O2 controllers that you can datalog with.
Balance? Individual carburation or variances in jetting between cylinders (which below you stated you increased rather than equalized) is not what effects the smoothness. Synchronizing the opening of the butterfly valves while achieving the highest idle via the fuel screws is what smooths out or "balances" the carbs to each other. Fuel delivery as controlled from idle to FWO by 4 circuits (5 if you include the start enrichener) have the greatest effect on mileage although a well fed, clean running engine is more efficient and thus should produce the best mileage.
When I changed my needles shims from having a .010" difference front to rear to having a .020" difference front to rear, I picked up 3-4 MPG and the engine ran noticeably smoother. I was pleasantly surprised, didn't think .010" could make that big of a difference.
Sometimes you get lucky with trying different setups trial and error. Best way to get the jetting and balance right is with a couple of wideband O2 controllers that you can datalog with.
Of course the luxury of a real-time CO / AFR measurement would be the best (followed by sniffing the pipes on a dyno which is diluted by the cross-over pipe) but few of us can afford the expense and still pay for fuel (here its still a minimum of $3.83 per gallon).
Skokievtr I must appologize, my comment about why you posted was a little off. For some reason when I posted about it being interesting that you posed such a questions when you were apparently overqualified to answer it I had it my head that you were the original poster. Going back and re-reading I see I was a bit off in my post. I appologize for that.
As for the deterioration in performance/lean detonation issues over the last couple of years it could also just be that the fuel quality has gone down hill overall.
I'm not sure about the entanol changing from summer to winter blends, I just know they use more oxygenation as you said and I was thinking off the top of my head it was from the ethanol. It could be from other additives though.
As for the deterioration in performance/lean detonation issues over the last couple of years it could also just be that the fuel quality has gone down hill overall.
I'm not sure about the entanol changing from summer to winter blends, I just know they use more oxygenation as you said and I was thinking off the top of my head it was from the ethanol. It could be from other additives though.
Last edited by skokievtr; 06-22-2012 at 01:05 PM.
06-22-2012 | 06:03 PM
#14
Senior Member
SuperBike
Joined: Mar 2007
Posts: 1,611
From: Belgium, WI
I will continue to be scientific in this, and my answer would be that I cannot tell you what the answer is with so little data and that to guess would be wild speculation at best. Here are possibilities:
1.you rode the bike "nicer"
2.octane helped
3.you were too lean and the jetting actually allowed you to reduce throttle and therefor fuel use
4. temperature played a role
5. all the above
6. none of the above
1.you rode the bike "nicer"
2.octane helped
3.you were too lean and the jetting actually allowed you to reduce throttle and therefor fuel use
4. temperature played a role
5. all the above
6. none of the above
06-22-2012 | 07:33 PM
#15
Slacker
Superstock
Superstock
Joined: Jun 2005
Posts: 489
From: San Antonio, TX
I wonder is adjusting the TPS down a little might help dial out the pre-ignition? That could be a better solution vs buying more expensive fuel.
In my workings with this bike, 1/4 turn on the fuel screw can produce significant changes to idle and cruise performance.
Skokie, are you running with an ignition advance rotor? Could excessive carbon buildup be contributing the issue?
In my workings with this bike, 1/4 turn on the fuel screw can produce significant changes to idle and cruise performance.
Skokie, are you running with an ignition advance rotor? Could excessive carbon buildup be contributing the issue?
06-23-2012 | 08:28 AM
#16
Member
Squid
Joined: Sep 2011
Posts: 48
skokievtr
"Balance? Individual carburation or variances in jetting between cylinders (which below you stated you increased rather than equalized) is not what effects the smoothness. Synchronizing the opening of the butterfly valves while achieving the highest idle via the fuel screws is what smooths out or "balances" the carbs to each other. Fuel delivery as controlled from idle to FWO by 4 circuits (5 if you include the start enrichener) have the greatest effect on mileage although a well fed, clean running engine is more efficient and thus should produce the best mileage."
Sorry, I should have been more specific and stated 'Air/fuel ratio balance in the midrange' instead of just 'balance', it may have made better sense.
Agree, this is the well known balance method you mentioned in your response, and does the job of balancing the pilot circuits and synchronizing the butterfly valves. And if it is done correctly, yes, you will have a noticeably smoother running engine. But lets think about the whole picture for a minute. Is this the only adjustment we have that 'balances' the carburation on an uneven firing V-twin engine? Is there anything else we should consider that can effect 'balance'?
In addition to the pilot circuits we have the main and the needle jet circuits. To optimize our carb setups, should we be concerned with balancing these circuits also?
Each cylinder has a unique fuel demand (not the same front vs rear), therefor they need to be jetted independently as if you are tuning two separate single cylinder engines. And efficiencies made to one cylinder usually effect the other cylinders jetting requirements. What a pain! No one said it was easy
If you have one cylinder running richer or leaner than the other in the midrange because the needle positions aren't optimized for each individual cylinder's fuel demand (which will be different on the VTR same as any other uneven firing V-twin engine), it will effect most noticeably how smooth the engine runs in that range. This is the balance I was referring to. And that's were we spend the vast majority of our riding time on the street.
FWIW I spent close to two years of my life developing fuel maps for the Buell 1125 Rotax V-twin engine, probably one of the most difficult engine designs to tune and balance. My tools on that project were dual wideband O2 controllers, a datalogging setup and computer, quite a departure from working with carburators, but the basic theory is the same. You learn alot when you can get actual readings and measure the effect of your changes. I guarantee that how well balanced you get your mid-range A/F ratio set for each individual cylinder will have a noticeable effect on how smooth the engine runs.
"Balance? Individual carburation or variances in jetting between cylinders (which below you stated you increased rather than equalized) is not what effects the smoothness. Synchronizing the opening of the butterfly valves while achieving the highest idle via the fuel screws is what smooths out or "balances" the carbs to each other. Fuel delivery as controlled from idle to FWO by 4 circuits (5 if you include the start enrichener) have the greatest effect on mileage although a well fed, clean running engine is more efficient and thus should produce the best mileage."
Sorry, I should have been more specific and stated 'Air/fuel ratio balance in the midrange' instead of just 'balance', it may have made better sense.
Agree, this is the well known balance method you mentioned in your response, and does the job of balancing the pilot circuits and synchronizing the butterfly valves. And if it is done correctly, yes, you will have a noticeably smoother running engine. But lets think about the whole picture for a minute. Is this the only adjustment we have that 'balances' the carburation on an uneven firing V-twin engine? Is there anything else we should consider that can effect 'balance'?
In addition to the pilot circuits we have the main and the needle jet circuits. To optimize our carb setups, should we be concerned with balancing these circuits also?
Each cylinder has a unique fuel demand (not the same front vs rear), therefor they need to be jetted independently as if you are tuning two separate single cylinder engines. And efficiencies made to one cylinder usually effect the other cylinders jetting requirements. What a pain! No one said it was easy
If you have one cylinder running richer or leaner than the other in the midrange because the needle positions aren't optimized for each individual cylinder's fuel demand (which will be different on the VTR same as any other uneven firing V-twin engine), it will effect most noticeably how smooth the engine runs in that range. This is the balance I was referring to. And that's were we spend the vast majority of our riding time on the street.
FWIW I spent close to two years of my life developing fuel maps for the Buell 1125 Rotax V-twin engine, probably one of the most difficult engine designs to tune and balance. My tools on that project were dual wideband O2 controllers, a datalogging setup and computer, quite a departure from working with carburators, but the basic theory is the same. You learn alot when you can get actual readings and measure the effect of your changes. I guarantee that how well balanced you get your mid-range A/F ratio set for each individual cylinder will have a noticeable effect on how smooth the engine runs.
06-23-2012 | 10:27 AM
#17
Banned
MotoGP
Joined: Aug 2007
Posts: 5,942
From: Lake View Terrace, CA
I will continue to be scientific in this, and my answer would be that I cannot tell you what the answer is with so little data and that to guess would be wild speculation at best. Here are possibilities:
1.you rode the bike "nicer"
2.octane helped
3.you were too lean and the jetting actually allowed you to reduce throttle and therefor fuel use
4. temperature played a role
5. all the above
6. none of the above
1.you rode the bike "nicer"
2.octane helped
3.you were too lean and the jetting actually allowed you to reduce throttle and therefor fuel use
4. temperature played a role
5. all the above
6. none of the above
You left one out.... the possibility there was a vacuum leak in the front cyl. before the carb swap....
06-23-2012 | 01:04 PM
#18
Senior Member
SuperBike
Joined: Mar 2007
Posts: 1,611
From: Belgium, WI
06-25-2012 | 11:56 AM
#19
Senior Member
SuperBike
Joined: Jan 2007
Posts: 2,168
See my replies in red
I actually (right or wrong) now have the identical "jetting" front & rear including 45 pilots, 180 main jets, .020" needle shims, 2.5 out pilot screw position AND longer intake velocity stacks (the rear stack also on the front carb), the only difference are the jet needles & needle jets. Consequently, the front/rear carburation is as close I will ever make it and the primary changewas 89 octane
Not likely given my TwinMax & mercury manometer read almost identical after as they did before the recent changes & I did not need to even touch the rear butterfly adjustment (sync) screw but did turn up the idle speed higher than before (which presumably hurts mileage)
We do the best we can. I'm going to check the plugs again after my very hot and fast ride Saturday, during which mileage did drop down to a low or 33.5 and high of 35.7. However, before the recent changes including 89 octane, I have run these same roads many times during similar temperatures and lower speeds and usually obtained at best 32 mpg and more often 30 or less...
I will continue to be scientific in this, and my answer would be that I cannot tell you what the answer is with so little data and that to guess would be wild speculation at best. Here are possibilities:
1.you rode the bike "nicer" just a touch but I still have been breaking a ton on every ride just to blow the carbon & cobwebs out
2.octane helped that is the key factor IMO
3.you were too lean and the jetting actually allowed you to reduce throttle and therefor fuel use I've run richer previously & still had pregnition
4. temperature played a role the unusually hot weather may have promoted better atomization but also detonation, particularly under low road speed & high load conditions
5. all the above see above
6. none of the above not likely
1.you rode the bike "nicer" just a touch but I still have been breaking a ton on every ride just to blow the carbon & cobwebs out
2.octane helped that is the key factor IMO
3.you were too lean and the jetting actually allowed you to reduce throttle and therefor fuel use I've run richer previously & still had pregnition
4. temperature played a role the unusually hot weather may have promoted better atomization but also detonation, particularly under low road speed & high load conditions
5. all the above see above
6. none of the above not likely
I wonder is adjusting the TPS down a little might help dial out the pre-ignition? That could be a better solution vs buying more expensive fuel. I have the TPS at about 440 ohms and can't get much lower
In my workings with this bike, 1/4 turn on the fuel screw can produce significant changes to idle and cruise performance. maybe with a 48 or bigger pilot but not with my bike & OE 45 pilot; .25 turns, the change on only the front carb, equates to 10% enrichening on only this circuit
Skokie, are you running with an ignition advance rotor? Nyet Could excessive carbon buildup be contributing the issue? I used a bore scope through the spark plug holes and when the carbs were off carefully looked at the intake valves, and everything I could see indicated little carbon or other deposits; which speaks well for Techron Concentrate+ usuage
In my workings with this bike, 1/4 turn on the fuel screw can produce significant changes to idle and cruise performance. maybe with a 48 or bigger pilot but not with my bike & OE 45 pilot; .25 turns, the change on only the front carb, equates to 10% enrichening on only this circuit
Skokie, are you running with an ignition advance rotor? Nyet Could excessive carbon buildup be contributing the issue? I used a bore scope through the spark plug holes and when the carbs were off carefully looked at the intake valves, and everything I could see indicated little carbon or other deposits; which speaks well for Techron Concentrate+ usuage
If you have one cylinder running richer or leaner than the other in the midrange because the needle positions aren't optimized for each individual cylinder's fuel demand (which will be different on the VTR same as any other uneven firing V-twin engine) I guarantee that how well balanced you get your mid-range A/F ratio set for each individual cylinder will have a noticeable effect on how smooth the engine runs.
Last edited by skokievtr; 06-25-2012 at 12:01 PM.
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