gas mileage

[Mike in AR]

Recently changed my slow jets out to 38's. Did not change out the main jets or the needles. Synced the carbs. turned the pilot screws to 1and 3 quarter turns. Put a K&N air filter in the air-box,(no prefilter) Gas mileage is only 29mpg. Is there something that I have over-looked. Oh yeah, bike has oem pipes on it. Back before my slow jets clogged up and the change to 38's, my mpg was between 32 and 36. Bike has been de-smogged, and the remaining vent hoses were checked out and looked good. What else can I do to get the mileage back up? All suggestions appreciated. TIA.

Mike

[John U.]

My Standard, now a Tourer with 38's at 1 3/4 turns out gets 36 to 38 depending on how much wrist I employ.
How is your air filter? Plugs, O-rings , vacume tubes and plugs, are the carb clamps tight.
A trigger wheel or ETC mod might give you more mileage. Speed and the wrist are the biggest factors.

[Mike in AR]

I usually keep my speed between 60 and 70, or lower. I travel mostly back roads, where the speed limit is normally 50-55. The plugs and vacume tubes all looked good, and the carb clamps were all tight, but I will go back and check it all again.  Thanks John. Any more suggestions on what to look for out there?

[John U.]

You could have a brake dragging. If the disks are real hot the problem could be that. If you can put the bike on a lift, see if the wheels seem to dragg too much, slight drag is normal. Otherwise,  it's mostly mundane stuff, check air preasure, run some Seafoam or Techron for the hell of it. Are you sure the snyc is good, check the upper carb clamps (there are two between the intake tubes and carbs). Check the plug conditon to see if they are all tan to light brown, you might have one not firing consistantly.
Good luck, let us know how it works out.

[Mike in AR]

When we changed the the tires, the wheels spun okay. Will go back and check the upper clamps on the carbs tomorrow after I get off work. Thanks for the help. Will keep checking different things. I have seen posts where a spacer was placed under the front of the gas tank. What is the purpose of doing this? TIA

Mike

[FLATSIX]

I have a '97 standard - K&N filter with the pre-filter in, cut the piggies - for the rest all standard.

Had once a trip with a group of motorcycles : gave me the best mpg ever : 32mpg.

For the rest I drive solo and not often - do always the same short trip (10 mile forward and 10 miles back = 20 miles/trip)- during that short ride and when motor warmed up (after 6-7 miles) I cannot help firing her up a little. So when I come back with warm motor my right-frist likes to turn many times while I enjoy acceleration = this brings me always to 28 to 24mpg !!

I think it is the way I drive : short distances - small roads with many stops + turning that wrist when I see an opening on the road - or my bike is not healthy..........

[Tundra]

Recently changed my slow jets out to 38's. Did not change out the main jets or the needles. Synced the carbs. turned the pilot screws to 1and 3 quarter turns. Put a K&N air filter in the air-box,(no prefilter) Gas mileage is only 29mpg. Is there something that I have over-looked.

  You did go up on jets, requiring more fuel. You did adjust your pilots, I'm guessing you turned them IN to 1 3/4. Where were the pilots at before your adjustment? I believe you said your bike was a '97? That year was built a little differant
(I like them better) However they did burn more fuel. It sounds wierd, some guys consistantly will get 38mpg while some others only get 32. The year of the bike, how it's set up (wieght/gear), modifications and riding style also play a role in your milage. Also, what kind of fuel are you running? Ethanol or non-ethanol? High test or regular? When I run hightest/premium it costs more, however my milage increases (pays for itself). I notice a decrease in both performance and milage with ethanol fuel. Sounds like allot of questions, hopefully they can help you pinpoint the decrease in milage.

[Robert]

Change the slow jets back. I recently put in a Factory pro jet kit and it includes the 38 slow jets and my mileage went to 30 from 33 to 35 mpg. The Factory kit includes needles and mains too but when I noticed a drop in mileage I really wondered if the culprit was the slow jets because with the needles adjusted they are actually set leaner than before. Even running in the midrange my spark plug color is whiter than before. If you have a jet kit installed with adjustable needles you might try leaning them out by one notch. Sometimes one notch may make to much difference and you can get washers that are half as thick as the needle adjustment and go like a half step. You more than likely will not be able to feel it and it will improve you gas mileage.

[John U.]

If you have 38 slows adjusted to 1 3/4 out it shouldn'y hurt your mileage, it didn't hurt mine. The 38s are just a bit more resistant to clogging, but the pilot screw adjustment should prevent a rich condition. As mentioned, check your plugs, if they show a rich condition maybe you can run at 1 1/2 out on the pilots.
The tank spacer prevents air starvation at full throttle and high speeds, ti won't make a difference in moderste running.

[Mike in AR]

Tundra, the jets were set at 2 1/2 with the #35's. We closed them up, and the re-opened them to 1 3/4. Ethanol is about all we can get where I live. Normally run reg., but will try a couple of tanks of premium to see if there is a difference. My bike is a '97 black and yellow, and even with the mileage problem, I would not trade it. For one reason, the wife would cause me bodily harm, that's how much she loves this bike.lol
Thank you for your input. I will post what ever results I come up with.

[Mike in AR]

Robert, don't remember if the needles were adjustable or not. Need to check that out. While it is not a good thing, it is good to know that this problem is not uniquely mine. I was afraid that we might have really messed something up. Thank you for your response.

[Zorba]

97's Cal models are set at 2 turns out from the factory not sure about reg 97's!
Did you take out the Foam Pre-filter on your K&N ,if not take it out that should lean you out a little and give you better milage or put in a "Dyna jet stage 1" kit and set them on the 3rd notch, if you have to set them on the 2nd notch with out the "Pre-filter" in the K&N and put a coule of washers under the front of your gas tank to grab a little more air

Or just play with the "pilot screw untill you find the right setting for your bike!?

[Bill Laslett]

Your needles are adjustable. you will need the missing clips and any other parts that were missing. Don't remember if you have all 6 needles, but do remember you were short some of the clips that go on the needles. Give HDL a call, they should replace them. Won't take much to change the needles. Don't have to remove the carbs again. You will have to pull your Dragon Bars off the top of each side.
   Bill

[Bagger John - #3785]

I changed my 2000 Interstate's slow jets to #38s last year. Idle air screws are now at 1 1/2 turns out; bike is stock with regards to intake and exhaust. Mileage went from ~38 to 30-32MPG. Power was noticeably increased in the lower RPM regions. An inspection of the plugs shortly after the jet swap revealed that all cylinders are burning as they should be.

FWIW, I'll gladly trade a little less mileage per tank for the ability to roll the throttle on and pass anything without needing to downshift first. Though it isn't much of an issue with our Standard and Tourers, the elimination of the I/S' 2000-3000RPM lean spot (and subsequent power jump) made the bike more suited to my style of riding.

[Bill Laslett]

Would a trigger wheel make gas milage improve? How about timing? Maybe a I/S or other ICM?

[John U.]

I hear that an appropriate trigger wheel will improve mileage. I know the ECT mod will, if you can control the wrist.