poor gas milage
08-06-2014, 10:59 AM
#1
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SuperSport
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poor gas milage
it's been a while since I did hawks carburetor set up and installed the handy dandy air mixture screws from jack flash. I've been making adjustments since the set up because I'm getting bad gas milage, I had hopes that the thumb screws would help because they are easier to adjust, no joy!
I'm getting about 78 to 90 miles per tank. I was getting the average 120 per tank prior to set up. I've done everything I can think of to resolve the issue and am thinking I may have to go back to the stock set up with the 45 slow jets and clear the slider hole I plugged on the front slide. (I have noticed the front slide returns slower than the rear. Any help is appreciated)!
I have balanced the carbs after every adjustment and checked for air leaks and fuel leaks, no joy.
I'm getting about 78 to 90 miles per tank. I was getting the average 120 per tank prior to set up. I've done everything I can think of to resolve the issue and am thinking I may have to go back to the stock set up with the 45 slow jets and clear the slider hole I plugged on the front slide. (I have noticed the front slide returns slower than the rear. Any help is appreciated)!
I have balanced the carbs after every adjustment and checked for air leaks and fuel leaks, no joy.
08-06-2014, 11:48 AM
#2
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08-06-2014, 12:07 PM
#3
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noticeably slower. When I had the cover off the air box and the stacks off, I depressed both front and rear at the same time and the front returns noticeably slower. I have had the slides out to shim the needles and it's possible I got the diaphragm in wrong or even tore it. I didn't check that. Thanks! I've gotten very good at taking the carbs apart so it shouldn't take any time to check.
08-06-2014, 01:00 PM
#4
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Squid
Join Date: Aug 2013
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as stated above, check your rear diaphragm. They tend to create tons of trouble. Also, maybe a long shot, make sure that your choke is not stuck (happened to me, pulled the carbs out without paying much attention to what I'm doing and the rear cylinder choke cable was in the way).
08-06-2014, 04:18 PM
#6
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It's a really, really good chance that it's just not seated properly. Most of the times pinholes and cracks come from old bikes that have been sitting or improperly cared for, and if you've had the diaphragm off it's pretty easy to install it improperly. But that being said, if indeed it turns out to be broken, I have a used extra lying around I think 
08-06-2014, 06:29 PM
#7
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It's a really, really good chance that it's just not seated properly. Most of the times pinholes and cracks come from old bikes that have been sitting or improperly cared for, and if you've had the diaphragm off it's pretty easy to install it improperly. But that being said, if indeed it turns out to be broken, I have a used extra lying around I think
08-06-2014, 06:37 PM
#8
Well take off, eh.
SuperBike
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When one of the holes is plugged on the front slide, it should be slower. This has been discussed in Hawks thread. However, it should still have a steady flow. Also, resistance while pushing it up should be the same as rear.
Before you go tearing up the carbs again, check it again.
Before you go tearing up the carbs again, check it again.
08-06-2014, 09:32 PM
#9
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When one of the holes is plugged on the front slide, it should be slower. This has been discussed in Hawks thread. However, it should still have a steady flow. Also, resistance while pushing it up should be the same as rear.
Before you go tearing up the carbs again, check it again.
Before you go tearing up the carbs again, check it again.
08-07-2014, 08:07 AM
#10
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SuperBike
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The pilot or "slow" jets shouldn't affect your mileage that much if at all. They are for 0% to about 25% throttle. The main jet is where you live most of the time. Gas mileage will be affected by the main jet size, and also the needle taper since that allows gas to flow.
Also greatly affected by your wrist....
James
Also greatly affected by your wrist....
James
08-07-2014, 03:11 PM
#11
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Superstock
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If you end up needing the Diaphram
Honda Motorcycle Parts 1998 VTR1000F AC CARBURETOR (COMPONENT PARTS) Diagram
part #22, $70, saves you $30 anyway. The shop is one not too far from me. I get all my stuff from them. They take a little bit longer to get stuff sometimes, but it ends up being worth it for how much you save
Honda Motorcycle Parts 1998 VTR1000F AC CARBURETOR (COMPONENT PARTS) Diagram
part #22, $70, saves you $30 anyway. The shop is one not too far from me. I get all my stuff from them. They take a little bit longer to get stuff sometimes, but it ends up being worth it for how much you save
08-07-2014, 05:49 PM
#12
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Location: Pompano Beach, Fl.
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it's been a while since I did hawks carburetor set up I may have to go back to the stock set up with the 45 slow jets and clear the slider hole I plugged on the front slide. (I have noticed the front slide returns slower than the rear. Any help is appreciated)!
I have balanced the carbs after every adjustment and checked for air leaks and fuel leaks, no joy.
I have balanced the carbs after every adjustment and checked for air leaks and fuel leaks, no joy.
Yes, that's what I did. Running too rich did nothing to enhance power and the mpg was about 30 for mine as well. The set up in my sig is the best, all things considered.
09-12-2014, 01:42 PM
#13
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OK, so it's been awhile since I posted; things got kinda nuts for a while and I haven't had time to ride or wrench. I did finally pull the carburetors and the diaphragms were OK. What I did find was the front air screw was missing the tiny washer that sits on the spring, not sure how that happened. Still, that wouldn't affect my fuel consumption I don't think , wouldn't that cause the bike to run a little lean?
09-12-2014, 05:34 PM
#14
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Just a thought. Have you asked Hawk or any one else that has done the re-jet as per his base line what they are getting for mileage?
Maybe that is all the 996 lump w/carbs can do when it's tuned that way.
I want EFI.
Maybe that is all the 996 lump w/carbs can do when it's tuned that way.
I want EFI.
09-12-2014, 10:55 PM
#15
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It's my understanding that the hawks carb tune shouldn't affect mileage much because the low speed jet only affects the bottom RPM range. I just need to examine everything more closely, I'm sure it's something simple like a hose not connected, (I did check all my vacuum hoses, heater hoses and fuel lines). I suppose it could be the "choke" but I didn't take the choke cables off but it's worth a look.
09-12-2014, 10:58 PM
#16
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The pilot or "slow" jets shouldn't affect your mileage that much if at all. They are for 0% to about 25% throttle. The main jet is where you live most of the time. Gas mileage will be affected by the main jet size, and also the needle taper since that allows gas to flow.
Also greatly affected by your wrist....
James
Also greatly affected by your wrist....
James
09-13-2014, 05:04 AM
#17
Well take off, eh.
SuperBike
Join Date: Jun 2012
Location: QC, Canada
Posts: 1,201
The opening of your fuel screws does affect gas mileage. They still keep providing fuel to the carbs even when open throttle.
Running the 48's will affect gas millage also. Now, the question you need to ask yourself is, do I want longevity on my gas tank, or, do I want to squeeze more power. If longevity is your main concern, return to stock set up as closely as possible, and, you should gain the mileage you're looking for.
I figure if you're running Hawks set up, he has made it very clear many times. It's in the ball park, but still needs to be fine tuned. No two bikes are the same. (if he allows me to quote him..)
So, if you have no bad running symptoms from 0 to WOT, then chances are you're on, or very close to your goal. Then, you may try turning in your screws by small 1/8 increments until it begins to have lean symptoms. bring it back to previous setting, and you should be good.
Get yourself fresh O-rings. This will improve your gas mileage.
Running the 48's will affect gas millage also. Now, the question you need to ask yourself is, do I want longevity on my gas tank, or, do I want to squeeze more power. If longevity is your main concern, return to stock set up as closely as possible, and, you should gain the mileage you're looking for.
I figure if you're running Hawks set up, he has made it very clear many times. It's in the ball park, but still needs to be fine tuned. No two bikes are the same. (if he allows me to quote him..
)So, if you have no bad running symptoms from 0 to WOT, then chances are you're on, or very close to your goal. Then, you may try turning in your screws by small 1/8 increments until it begins to have lean symptoms. bring it back to previous setting, and you should be good.
Get yourself fresh O-rings. This will improve your gas mileage.
09-13-2014, 11:34 AM
#18
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SuperSport
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Join Date: Jul 2012
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The opening of your fuel screws does affect gas mileage. They still keep providing fuel to the carbs even when open throttle.
Running the 48's will affect gas millage also. Now, the question you need to ask yourself is, do I want longevity on my gas tank, or, do I want to squeeze more power. If longevity is your main concern, return to stock set up as closely as possible, and, you should gain the mileage you're looking for.
I figure if you're running Hawks set up, he has made it very clear many times. It's in the ball park, but still needs to be fine tuned. No two bikes are the same. (if he allows me to quote him..)
So, if you have no bad running symptoms from 0 to WOT, then chances are you're on, or very close to your goal. Then, you may try turning in your screws by small 1/8 increments until it begins to have lean symptoms. bring it back to previous setting, and you should be good.
Get yourself fresh O-rings. This will improve your gas mileage.
Running the 48's will affect gas millage also. Now, the question you need to ask yourself is, do I want longevity on my gas tank, or, do I want to squeeze more power. If longevity is your main concern, return to stock set up as closely as possible, and, you should gain the mileage you're looking for.
I figure if you're running Hawks set up, he has made it very clear many times. It's in the ball park, but still needs to be fine tuned. No two bikes are the same. (if he allows me to quote him..
)So, if you have no bad running symptoms from 0 to WOT, then chances are you're on, or very close to your goal. Then, you may try turning in your screws by small 1/8 increments until it begins to have lean symptoms. bring it back to previous setting, and you should be good.
Get yourself fresh O-rings. This will improve your gas mileage.
09-16-2014, 08:02 PM
#19
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I think I finally have the air screw settings just right! I'm getting 36 MPG and better if I keep a light hand. I adjusted the air screws per the technique in the Honda manual and then fussed with it a little more. The bike is running great, no farts, hiccups, stalls and other assorted tics. Problem is, now I'm wondering if I can make it even better by fiddling with the shims on the needles.
09-18-2014, 07:51 AM
#20
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Superstock
Join Date: May 2012
Location: UK
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Your thinking dirt bikes. These have fuel screws as the adjustment is on the engine side not airbox. When you undo the screws (counter clockwise) your adding more fuel to the mix.
Good to hear your getting somewhere, but now you have started you wont stop tinkering LOL Just remember if you go adjusting your needles you will then end up going back and adjusting the A/F again. Needle height will also have an effect on the mains.
(:-})
Good to hear your getting somewhere, but now you have started you wont stop tinkering LOL Just remember if you go adjusting your needles you will then end up going back and adjusting the A/F again. Needle height will also have an effect on the mains.
(:-})
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