Improving gas mileage...

I've improved gas mileage now on about 12 bikes. This works especially if you are under 40 mpg. I'm consistantly getting mid to high 40's on all my 1100-1200's.

Easy 1-2 Hour job

1. Remove the carb cap, 4 screws.

2. Remove the spring.

3. Remove carb slide and diaphram, it's black with a needle hanging out the back.

4. Remove the jet needle, there's a large screw inside the middle of the carb slide holding it in.

5. There is a white spacer under a circle clip. Remove it.

6. Replace the white spacer with any small washers about 1/2 the thickness of the white spacer under the circle clip.

7. Ignore the fact that the white spacer has a small tit on one side.

8. You may want to add extra washers on top of the circle clip. (I didn't on my Venture and a friends)

9. Put it all back together in the same order it came apart. New washers, jet needle with circle clip tight (check it), 1 or more washers on top of circle clip, small spring, plastic screw, in that order.

10. Carefully reinstall slide and diaphram. Notice diaphram has a tap.

10. Do only one carb at a time. (Can use others as reference)

11. Go for a ride checking gas mileage and performance. My friends 87 Std. went from 37 to 45 mpg.

12. Clean and check spark plugs before and after. Correct color is gray, tan or clean depending on type of gas used. Slightly white electrodes is Ok if the plug base near threads is darker. white base and tip is too lean; black is too rich.

13. SO: Add washers under circle clip to richen, remove washers to lean.

14. My bike is faster now lean (hotter combustion)

15. I set pilot jet screws to 1 3/4 turns out

16. All 4 Ventures were way out of synch before I did them. Much smoother now.

Questions? Send me a PM or email: chuckfrench48@gmail.com (mention VR)

So, removing shims from under the needles is what you're saying.

I have done this and it worked for me. On my 1990 I have most of the original carb setup (1983 style) pilot jets 42.5 and the 180 air jets I did not use the needles though. My mileage cruising at 70 mph (GPS speed my speedo is off about 10 mph says I'm doing 80 mph) at 4000 rpm was around 34 mpg. I lowered the needles using 2 brass washers in place of the plastic spacer. 1986-1993 do not have adjustable needles, 83-85 do and they have a more aggressive taper to them then the 86-93 do. I needed to put a couple washers on top of the c clip otherwise the needle will wobble around and up and down. Mileage now is 40-43mpg. So I have to say it worked for me.

...I basically have the same setup on my airhead beemer..The needle has 4 notches, the higher you set the notches the lower the needle and the better the mileage..as you pointed out its best to check the plugs after lowering the needle to make sure its not running too lean..I improved my mileage on the Beemer about 6-8 mpg...It never occurred to me to replace the white spacer with a thinner washer on the Venture..Its got to work the same as the Beemer carb by lowering the needle....Thanks for the tip..I love this site

However, I would Sync the Carbs First, ( correctly )

Make sure the " idle Mix jets are set correctly "

Run couple hundred miles, then pull the Plugs, and see how they look. As to Rich, or Lean -----

Now, decide --- IF -- you want to go Leaner.

1986-1993 do not have adjustable needles, 83-85 do and they have a more aggressive taper to them then the 86-93 do.

Could the same not be accomplished on a first generation then by swapping out the needles with those from a second generation?

Could the same not be accomplished on a first generation then by swapping out the needles with those from a second generation?

Dont have a set of 2nd gen needles. I have a set of 83-85 more taper to them then 86-93 more power but less mileage I would suspect.

So then what would we do for 86-93 carbs:think:

So then what would we do for 86-93 carbs:think:

I just used the regular needles that came with the 1990 and did what 5bikes describes and it worked for me. I just happen to put in 83 pilot jets and air jets.

a couple of the plugs are black and smell of fuel,bigtime this means she running rich,right?How do you lean it out a bit?1987 1300cc What do yall recommend?

clean the Carbs completely

This is exactly the reason I signed up. My VR gets about 32-35 mpg but runs fine.

I am going to change the diaphrams adjust the carbs and mess with the needle. I had he carbs rebuilt about a year ago no real gain. The blue beast runs rich puffing smoke when I throttle up, blowing black goo on the floor when i fire her up in the morning.

thanks Stu:thumbsup:

I was going to do a write-up on the mod as I cought this thread the first time it came around when I had some hard data. The weather here has been so bad that I havn't gotten much riding in since I did it but here is the "How TO". I would like to say a BIG THANK YOU to Chuck (5bikes) for the write-up as I would have never thought of this myself. The pics are for the 86' to 93'VR's with the un-adjustable needles in the sliders.

Questions, PM me,

Earl

Sounds like what I'm going to do, mine also spits black out the pipes alot, and seems like its missing while holding steady rpms around 3 g's. I'll do this as part of my carb rebuild this year.

Sounds like a reasonable thing to try.

One other possibility. Has anyone tried checking the spring free length? If it is too short, the spring will be weaker and the slide will open too aggressively. I was thinking of stretching it, but can't see a figure in the manual for the standard length.

[edit - forgot to mention - another possibility which can damage your mpg is that the o-ring around the needle nozzle has perished allowing excess fuel to escape into the carb. Unless you can see extra fuel running down the bore, I do't know how you can check this, though.]

Hey Greg,

I too was concerned about those O'Rings as well and borrowed a "Bore Scope" from work and examined those O'Rings VERY CLOSELY (50X View.) on both my 86'VR and 87'VRs with the mileage at 95,000 plus on the 86'VR and 74,000 plus on the 87'VR and found that both sets of O'Rings looked like brand new. I touched them with a pick and they appeared to still be pliable and the "Bore Scope" confirmed that they were not damaged in any way. Now this is not a guarantee that your O'Rings are in the same condition, and if I was doing a total rebuild on the Carb. set I would not hesitate to replace them with new ones supplied with the rebuild kit, but I would say that if you see no obvious damage with the naked eye then you can be relatively sure that the O'Rings are still in usable condition. That was the case when I did the Needle Mod on both the 86'VR and 87'VR.

Earl

On mine they had hardened and taken a set from the position they were locked in - effectively triangular in cross section. I didn't have a rebuild kit and only had thicker o-rings, so I had to stretch a smaller diameter o-ring (so it was therefore thinner) to make it the right size.

Technically it should be fine, but if I can get the right bit I'm expecting to change it before my next long trip in the Summer.

So far, though, nothing I've done seems to have made a difference.

So Greg, you're aware that there's been some measure of success with leaning out the needles, right? On my 87 I lowered them a total of .050" for a gain of close to 10%. I also curtailed my throttle hand for another gain of 5%+. Of course, you don't want to end up too lean as engine damage can occur.

Jeremy

Just wondering how this has worked for the people that did this earlier this year. I am getting ready to replace the diaphragms on mine and am looking to lean it out a bit as the muffler tips are sooty and mileage is in the 37mpg range. I plan on installing new plugs and checking them regularly too.

Just looking for some feed back on this is all.

Thanks

Rick F.

I have a 97 RSTD and don't see any washers on the needles. Any one know why?

I'm surprised someone hasn't made an adjustable needle kit for this carburator make. The last bike I worked on the carbs (Honda I think, maybe a Triumph) had numerous slots in it for the circlip to adjust the highspeed mixture

I'm surprised someone hasn't made an adjustable needle kit for this carburator make. The last bike I worked on the carbs (Honda I think, maybe a Triumph) had numerous slots in it for the circlip to adjust the highspeed mixture

But this Bike was before EPA Regulations came in Charge ?

Anyone have any details on doing this to a 83-85? I am getting ready to replace my diaphragms in a few days and hope to do this at the same time.

Anyone have any details on doing this to a 83-85? I am getting ready to replace my diaphragms in a few days and hope to do this at the same time.

Yours should have adjustable needles already.

Did the 5bikes modification to my 2005 RSTD during my spring tune up. After cleaning and regapping the plugs (original) I replaced the carb plastic washer with a #4 stainless steal washer I found at Lowes. 1 tank of gas later, 171.3 miles without hitting the researve tank, I achieved 45.3mpg up from 38mpg. Happy about that! I just pulled the plug and would like some interpretation!

Thanks all and especially 5bikes!!