Improving gas mileage...update

[WiVR]

I had the same hesitation off idle problem. When I replaced my diaphragms I went to 2 washers, then 3. My bike likes the stock set up better. I am averaging around 42-43 MPG with the stock spacer.

[Smitty161]

Each time I dink with the carbs I check the sync. The bike is right on.

 

Honestly, I don't have a caliper, I did not notice that much of a difference in thickness between 3-#4s and the stock spacer. I used to average about 36 - 38mpg and it has dropped to a solid 33mpg. At the higher mpg the bike had new plugs and ignition wires. Still does. Ah my journey continues.

 

So am I to understand that the diaphrams, with no holes, should be good to go?

 

And of course, possibly, go back to the stock set up?

 

I believe the bike should do better than 33mpg. Any more ideas guys & gals?

Jonathan

[Venturous Randy]

Jonathan,

I believe you should be getting better than 33mpg.

The last time I got that bad was on a trip out of Birmingham, AL on the interstate trying to keep a head of a real bad storm coming in from my left. I ran for about 80 miles and did not get below 90mph, and some a bit more than that. At that speed an 83 tends to use a lot of gas.

RandyA

[StarQ]

Have you changed the gas you're using? Has the gas station changed the fuel mixture? I.e. Added alcohol?

 

Also, I read elsewhere on here that some bikes get better gas mileage with 87 octane than they do with 92.

 

I believe the bike should do better than 33mpg. Any more ideas guys & gals?

Jonathan

[Gearhead]

Johnathan, what happened when your mileage went down? Did you change anything? Did it start running differently? Did your riding habits or primary route change?

 

I think "crinkled" is the normal state for used diaphragms. Hold them up to a light to lood for small holes. No holes, no problem.

 

Randy, I ran at speeds of 85-90 one trip in 107 deg heat. I tried to outrun the dad gum heat, but just couldn't seem to get ahead of it :-) My 87 got 27 mpg - ugh.

 

Jeremy

[Venturous Randy]

 

Randy, I ran at speeds of 85-90 one trip in 107 deg heat. I tried to outrun the dad gum heat, but just couldn't seem to get ahead of it :-) My 87 got 27 mpg - ugh.

 

Jeremy

 

My run was several years ago when Alabama, Mississippi and Louisanna were getting hurricanes and tornados. In front of me was blue skys, to my left was the biggest, blackest cloud bank I can ever remember and close behind me, the interstate disapeared into a deep grey abiss.

I was able to stay enough ahead of it until it crossed behind me and it ended up doing a lot of damage in North Georgia.

That was the hardest I have ever run my bike for an extended period of time. I remember how slow 70mph felt when I finally slowed down.

RandyA

[Smitty161]

Nothing new was going on with the bike. I did do a teardown to check and fix any encountered problems. Had the front forks off. Did the steering head, springs and oil. Rear wheel was off. Pulled the driveshaft for inspection and greased it up. Brakes all the way around. The long trip I just took was stormy. Winds encountered every day. We did spend a lot of time up around 80-90mph. Am I just fretting over nothing??? The only thing I remember doing.....gave myself a major DUH....when I reassembled everthing I used the wrong grease on the axles. I used the moly-whatever stuff that I put on the driveshaft to cut down wear. My trip was the next day so I left it alone. Hopefully not a big oops. I plan to disassemble and rectify.

Jonathan

[Gearhead]

Jonathan,

 

If you're doing 80-90 then 33mpg is to be expected, at least in my experience. When you get 36-38 are you going slower? Speed is HUGE in gas mileage. My only other thought is that your brakes are dragging, but replacing the pads really shouldn't cause that.

 

You used moly grease on the axles - is that the grease problem? Do you mean the axle bolts that go all the way thru each wheel? The type of grease there doesn't matter, it's mainly to prevent corrosion. The wheel doesn't turn on the axle per se, but on the bearing.

 

Jeremy

[Smitty161]

Thanx Jeremy.....I'm so excited about the bike...my very first one so I'm overthinking it and seem to be chasing rabbits. If I'm going to speed suck it up and accept the mileage.

Thanx for all the input guys!!!! Hopefully my journey through this bike will allow me to return the favor someday.

Jonathan

[a1bummer]

Hey Randya, You said, "I replaced the .123 thick washer on the needle with three #4 washers that came to about .093." I assume your talking inches, right? I picked up some nylon spacers the other day at the hardware store for $.09 a piece. They measured 1.62mm (0.064"), +/- 0.01mm. When I measured the stock washers they were 2.5mm (0.098"), +/- 0.01mm. That's just 0.005" diff between my start and your end. I also check the stock washers on a set of carbs from an 83 I had handy. Again, the same. Now I'm wondering why the big diff between yours and mine. I went ahead and swapped them even though I felt the new shims seemed to be to thin. It dropped my idle quite a bit, (to 500-600 rpm's). I turned up the idle screw quite a ways and am still not where I want to be, (1100 rpm's). plus there is a bit of hesitation I don't like. So 1.62mm is obviously way to thin. Now I'm gonna go add another 0.53mm washer, (which will bring it to 2.15mm, (0.085")), to my shims and see what happens then. OK! I just measured the little nub on the stock washer and came up with 3.08mm (.1215"). I was measuring just the flat area. Now that I think about it, I could just cut off the nub on the stock washers to bring them down to 2.5mm.

[cimmer]

I thought I would add to this post with my experience with replacing the plastic fitting in the carbs with some brass #6S washers. I measured the plastic fitting to be 2.6mm on my carbs. I ended up using 3 of the #6S brass washers and each one ended up being .6mm thick. With 3 of them I was at 1.8mm. I did this to all 4 carbs and was able to get my mileage up from 36-38 to 46MPG. Engine runs strong and seems to be responsive also. I did replace the diaphrams with the new ones. I have driven roughly 500 miles and mileage is stay stable at 46mpg and speed have been averaging around 60mph.

I havent pulled the plugs yet but plan on that at about 1000 miles and will let you know what I find.

Thanks to everyone for suppling information about this as I am sure it wasnt something I would have tried on my own.

Rick F.

[Yammer Dan]

After talking to Skydoc at the Skid-In I think I understand this. Going to drop mine about .30 and see what happens. I already get in the high 40's when someone holds me back. Coming back from Ashville last year on one tank I got over 50. Beat "Brown Sugar" on that one and that is hard to do on MPG. But he was riding 2 up.

[MasterGuns]

I finally got to test the mileage my 86 is now getting after installing this #4 washer slide needle mod. Filled the tank to nearly running out and took off on a 98 miles run mostly down Interstate 20 West. Was running mosting 75 mph up to 80 mph (one up) in temps well over 100, then took Highway 4 up to Palo Pinto. Highway 4 is about 20 miles of ever increasing elevation and lots of great twisties. I ran pretty strong while climbing. Got to the top and headed back East down Highway 180 again between 70 and 80 mph. Returned to the same gas station I had last filled up at and refilled, again to a level that the fuel was almost running over the rim. Total miles run, 98 miles and amount of fuel used 2.67 gallons. Average mpg = 36.7.

 

My questions to all of you claiming to be gettng well over 40 mpg after this mod, just how are you driving or better put, under what conditions are you guys using to determine mpg? Are you running a flat 60 mph, perhaps 65 on flat roads? What is the temperature? I suppose I should retest mine at a flat 65 or maybe even 60 or maybe even 55 mph like the EPA does automobiles are report back. I just need to know if my results are acceptable under the riding conditions I reported. OR is something wrong with my bike and should I have gotten better mpg?

 

All this is really not a big deal to me as even 37 is acceptable. I am only curious and everyone know how that goes. Thanks

[Condor]

All this is really not a big deal to me as even 37 is acceptable. I am only curious and everyone know how that goes. Thanks

 

I think no matter what you do on the washer mod, high speeds and pulling grades will be the death knell to MPG's. Especially anything over 70 in 5th gear. I also think that no matter how you ride your gas milage will probably be better after the mods. It would have been better to run that route before the mod and then after to get a good comparison..... I think....

[CrazyHorse]

I find my mileage really suffers when I get over 4200 rpms speed unknown actual spedos way off.

[Venturous Randy]

The two fillups I have done since the mod is about 5 mpg better than before. Running the twisties and up and down mountains yesterday in NC, I filled up and got 43 mpg in what would have usually been at best 38mpg. This was mostly from 20 to 60 mph and a lot of pulling. I really can tell a difference as I still have two bars left at about 140 miles and in the past I would have been in on the last bar for a long time, getting ready for the light to start blinking. I also feel the bike is smoother than before.

The only negative I have seen is when I replaced the diaphragms, I felt an increase in power at WOT(wide open throttle). I do feel I have lost a bit of that and am wondering if the needles being a little deeper in the jets is what is making the difference.

RandyA

[Gearhead]

Randy, is it possible that your perception of increased top end was actually due to a hole in the mid-range power? And vice-versa, now that your mid-range is back? At WOT and higher rpm's, my understanding is that needles are out of the equation - it's all main jets at that point.

 

Masterguns, your mileage is not far from what I get on my 87 under the conditions you described. Mine might beat that by one or two points at best, maybe not at all. Those temps hurt my mileage. Before lowering the needles I averaged about 3 mpg less than I do now.

[MasterGuns]

Jeremy,

 

When I have time, I am going to take her out again but this time take the back roads; a route where I can take it easy and not have to run in the 70 mph speed zones. Heck even though it is posted 70 most traffic is running 80+. I want to re-assess this bike's mileage more realistically. Will report back. I also need to pull a couple plugs and take a look see at how they are burning at the leaner needle setting.

 

 

Randy, is it possible that your perception of increased top end was actually due to a hole in the mid-range power? And vice-versa, now that your mid-range is back? At WOT and higher rpm's, my understanding is that needles are out of the equation - it's all main jets at that point.

 

Masterguns, your mileage is not far from what I get on my 87 under the conditions you described. Mine might beat that by one or two points at best, maybe not at all. Those temps hurt my mileage. Before lowering the needles I averaged about 3 mpg less than I do now.

[Gearhead]

Speed is killer on MPG. I'd guess the optimum is around 50 or 55. I think that over 65 the downward slide of MPG gets pretty steep.

 

5bikes, who started this craze of lowering the needles (Thanks Chuck!) was writing about 47 or 48 average, but he was also riding 50-60, all the time as far as I could tell. I ride almost exclusively commuting, about 1/3-1/2 Interstate. I usually push 80-85 on the Interstate and 10-15 over the limits on surface streets and rural roads, with moderately spirited acceleration. Not a good habit, but so be it. 5bikes convinced me to try a tank at lower speeds. So I ran 60-70 Interstate and gently up to the limit on other roads and improved from about 40 average to 43. That's after lowering the needles by .050".

 

Jeremy

[bobcat]

My bike must be an oddball..it doesn't seem to matter if I average 70 or 80 mph my gas mileage stays at 40mpg with little varience..When I add gas I can take the gallons used, multiply it by 4 and it will equal the amount of miles..(within 1-2 miles)sometimes much to my amazement...

I've been following this shim post and although I'm tempted to modify the needles I think I'll leave well enough alone.....