Needle Shim Mod

[MasterGuns]

Before installing the needle shim mod my mileage was somewhere right around 32 mpg. That mileage was determined by filling my tank nearly to the brim, riding at 70 - 75 mph and until my fuel warning light came on; filled up to the brim again, and did it all again; four times. So, I've had these shaved down vinyl shims, purchased here on this site, for some time and decided just tonight to install them. It's done! Heck I am not even sure how much difference there is between the new shims and the stock one. I know stock is .112 in.

 

At idle, of course there would be no difference. Initially it does not seem to rev as quickly as it did before the mod; seems to be too lean now, stutters and bawgs some. Inserting three fingers in the air intate improves its ability to rev. Anyway, I will take it out on the road and run a few tanks through it and report back how this mod affects its mileage and performance. Hope this was worth the time involved working in a garage at 105 degrees. Oh, all the evaluating will be minus the plastic just in case I have to go back to stock.

[jasonm.]

you say .112" was original. But my original was .122 including that tab the make the whole thing "cocked". Using all the proper measuring tools. I droped Mine just approx. .020 = approx.100" and does not studder or bawk. I was getting 36 or 37 hiway mpg before. I suspect I will gain 2 mpg on the hiway. I had it EGA'd during this MOD. And anything more than .020 drop was too lean. The EGA does not lie and took the guess work out of this process....FYI, the reason for the the "not reving as quickly. You have eliminated excess fuel in the system. A rich system responds faster than a lean one as the throttle is opened. Due to the air instantly making the system closer to the 13 to 1 ideal power ratio. Rather than the possible 12 to 1 you have been running. Mine is running 13.6 :1 most of the time cruising now.

Edited July 21, 2010 by jasonm.

[skydoc_17]

Hey Herb,

Try Adjusting the Idle Mixture Screws OUT 3 Turns from bottom. On a few bikes, I have gone out as much as 31/2 turns, use 1/4 turn increments for this adjustment. Checking your Carb. Sync. is another good thing to do seeing as how you already have your side covers off the bike. This Needle Shim Mod works best if your Carb. Diaphragms are functioning properly with NO holes in them. As with EVERYTHING I sell on the VR.ORG site, if you are not happy with the way a mod or kit functions, I will gladly refund your money.

Earl

Edited July 21, 2010 by skydoc_17
CRAYON BROKE!

[bald josh]

I agree with skydoc on the sync, after i did the mod to mine the bike ran pretty poor, hooked up the sync and they were way off. after a sync it ran fantastic!

[MasterGuns]

you say .112" was original. But my original was .122 including that tab the make the whole thing "cocked". Using all the proper measuring tools. I droped Mine just approx. .020 = approx.100" and does not studder or bawk. I was getting 36 or 37 hiway mpg before. I suspect I will gain 2 mpg on the hiway. I had it EGA'd during this MOD. And anything more than .020 drop was too lean. The EGA does not lie and took the guess work out of this process....FYI, the reason for the the "not reving as quickly. You have eliminated excess fuel in the system. A rich system responds faster than a lean one as the throttle is opened. Due to the air instantly making the system closer to the 13 to 1 ideal power ratio. Rather than the possible 12 to 1 you have been running. Mine is running 13.6 :1 most of the time cruising now.

 

 

I think that little tab on the OEM spacer recessess into a hole down inside the slide so I didn't count that. Am I screwed up here?

[MasterGuns]

Hey Herb,

Try Adjusting the Idle Mixture Screws OUT 3 Turns from bottom. On a few bikes, I have gone out as much as 31/2 turns, use 1/4 turn increments for this adjustment. Checking your Carb. Sync. is another good thing to do seeing as how you already have your side covers off the bike. This Needle Shim Mod works best if your Carb. Diaphragms are functioning properly with NO holes in them. As with EVERYTHING I sell on the VR.ORG site, if you are not happy with the way a mod or kit functions, I will gladly refund your money.

Earl

 

Shoot, I'm not worried about anything not working properly things just need to be tweeked some I suppose. Glad to have gotten these shims from ya. Thanks again. Anyway, I will do as you say and move the idle mixture screws out 1/4 turn CCW and see what happens. Don't really recall where they are now. I think three are at 2 1/4 and number four is at 3 already; why (????). Diaphrams are almost brand new and still looked perfect last night so that is not a concern. I will also sync the carbs again; I just synced them about 10 days back. If still not satisfied after all than I may add a #4 washer to your spacers and see if I get any improvement.

 

Thanks Earl and I will post my results.

[jasonm.]

I think that little tab on the OEM spacer recessess into a hole down inside the slide so I didn't count that. Am I screwed up here?

There a 2 projections on the stock shim. One is pointed. THAT one goes into a tiny hole in the slide. So that does not apply. The tab that is slightly raised, is sort of square. It is design to angle the needle in the needle jet. WHY you ask? It's to confine wear to one side and/or help resist gravity pulling the needle to the "down side" all the time. In any case...there is a reason. May not be clear to us all. But it's there. After having this bike 20+ years and taking the carbs apart MANY times for MODs rebuilds and such...I know what's what. ANy bucking or surging...is not good.aka too lean. I use a combination of #6 stainless and #6 nylon plastic shims.The thicknesses can vary. The plastics varied from 1.6mm to 1.75mm. The SS shims .7mm to .9 mm. So walking into the hardware store with a micromenter or ditital caliper helps a lot. I only needed one of each per carb. Take your time. Do it in steps and have a good measuring tool. ALSO, adjusting the low speed screw HARDLY affects mileage or any running much above 1800rpm. That screw is something you can see when the carbs are removed. It's only one tiny little hole FOR IDLE. ANd the screw fits into it. But up stream there are 3 more holes grouped together. Those are your TRUE low speed OPERATION holes above 1/8 or 1/16 throttle.

Edited July 22, 2010 by jasonm.

[MasterGuns]

Well, just got back from the garage where I reinstalled the OEM needle shims. Tried everything to get things to smooth out with no backing firing, popping at idle and the hesitation when hitting the throttle from medium to hard. Moved the idle mixture screws all the way out to over 4 turns. Resynced the carbs, which were almost perfect anyway, and still no improvement. Heck, I could even feel an increase in engine heat just sitting next to the running motor due to much leaned out fuel mixture. So, rather than mess with it by taking each valve assembly apart to add additional washers to move the needles outward little by little, I decided to leave well enough alone and just reinstalled the stock shims. Did so and she loves them. No hesitation, no popping and backfiring. Oh well, I have to settle with the 32mpg.

[CrazyHorse]

Well, just got back from the garage where I reinstalled the OEM needle shims. Tried everything to get things to smooth out with no backing firing, popping at idle and the hesitation when hitting the throttle from medium to hard. Moved the idle mixture screws all the way out to over 4 turns. Resynced the carbs, which were almost perfect anyway, and still no improvement. Heck, I could even feel an increase in engine heat just sitting next to the running motor due to much leaned out fuel mixture. So, rather than mess with it by taking each valve assembly apart to add additional washers to move the needles outward little by little, I decided to leave well enough alone and just reinstalled the stock shims. Did so and she loves them. No hesitation, no popping and backfiring. Oh well, I have to settle with the 32mpg.

 

32 still seems to low.

[Venturous Randy]

I guess I am one of the lucky ones on the shim mod. I replaced the nylon washer with about three washers and went from about .123 to about .093 in thickness after trying even thinner. The bike runs very good and my mileage went from about 38/42mpg on a real good ride to now having rides at almost 49mpg and this is two-up. I have not went on many rides with continued speed in the 70 to 80 mph range, like on an interstate, but the rides thru the mountains running 40 to 55 are doing great. But, in the 70 to 80mph rides before, I bet I was not getting as good as 38mpg.

Oh, and I am still cranking it on fairly routinely and not babying it.

RandyA

[Condor]

Well, just got back from the garage where I reinstalled the OEM needle shims. Tried everything to get things to smooth out with no backing firing, popping at idle and the hesitation when hitting the throttle from medium to hard. Moved the idle mixture screws all the way out to over 4 turns. Resynced the carbs, which were almost perfect anyway, and still no improvement. Heck, I could even feel an increase in engine heat just sitting next to the running motor due to much leaned out fuel mixture. So, rather than mess with it by taking each valve assembly apart to add additional washers to move the needles outward little by little, I decided to leave well enough alone and just reinstalled the stock shims. Did so and she loves them. No hesitation, no popping and backfiring. Oh well, I have to settle with the 32mpg.

 

Herb, check the choke linkage to see if the rods are coming all the way out when the choke is completely off..... I've seen a few posts in the past where this caused poor milage because the choke was still partially on when the lever wasn't....

[MasterGuns]

32 still seems to low.

 

 

I got this mileage while on an interstate highway running no slower than 75 but mostly even higher. Is 32 mpg still to low? Just curious. I's sure that if I were to run slower my mpg would increase.

[Condor]

I got this mileage while on an interstate highway running no slower than 75 but mostly even higher. Is 32 mpg still to low? Just curious. I's sure that if I were to run slower my mpg would increase.

 

When runing 75 out on the flats I'll get 38mpg on the '83. 5th gear/4000+rpm. Slower, and in the twisties, using 2nd-3rd- and maybe 4th, I'll get 50mpg. So yeah your mpg will get better, but who wants to do 55mph on the interstate.... 32mpg is still too low. Check the choke...

[jasonm.]

Well, just got back from the garage where I reinstalled the OEM needle shims. Tried everything to get things to smooth out with no backing firing, popping at idle and the hesitation when hitting the throttle from medium to hard. Moved the idle mixture screws all the way out to over 4 turns. Resynced the carbs, which were almost perfect anyway, and still no improvement. Heck, I could even feel an increase in engine heat just sitting next to the running motor due to much leaned out fuel mixture. So, rather than mess with it by taking each valve assembly apart to add additional washers to move the needles outward little by little, I decided to leave well enough alone and just reinstalled the stock shims. Did so and she loves them. No hesitation, no popping and backfiring. Oh well, I have to settle with the 32mpg.

 

THE LOW SPEED SCREWS DO NOT EFFECT running past 2500rpm. 4 turns out is way rich. You are playing with 2 adjustments at the same time....needles and low speed. NEITHER EFFECTS THE SYNC. significantly. Popping is usually a lean condition...I had a leak in my boost sensor for years. I had a popping and hesitation for years if I did not let it warm up enough. Just fixed it last year. The shims are not the "FIX ALL" for every problem. Sounds like you are, "lean on the bottom and rich on top." Sounds like you have multiple issues and causes. My choke plungers were leaking until I diagnosed that this year. Now, It's smooth city. Whether I twist the throttle hard or soft. BUT I totally tore thru my carbs multiple times to find all the issues. Bad, float and float needle was a big issue that took 3 tear down times to find. Both these will cause BIG TIME rich issues .

Edited July 25, 2010 by jasonm.

[cimmer]

Just a thought here.. How are your spark plugs looking. When I did my mode I replaced the plugs also so I would have fresh indicators to check. The ones I removed where carboned up a bit so that is why I replaced mine. I am now getting in the mid 40's running close to 70 mph on the interstates.

Rick F.

[jasonm.]

Just a thought here.. How are your spark plugs looking. When I did my mode I replaced the plugs also so I would have fresh indicators to check. The ones I removed where carboned up a bit so that is why I replaced mine. I am now getting in the mid 40's running close to 70 mph on the interstates.

Rick F.

Good idea. You should always start with new plugs because any brown color on the tip area is permanent once it's there. Sort of like baking bread. Once it's brown...you can't go back.

[GilbertHall]

I got this mileage while on an interstate highway running no slower than 75 but mostly even higher. Is 32 mpg still to low? Just curious. I's sure that if I were to run slower my mpg would increase.

 

I'm waiting for the shims to arrive from sky doc. ran a tank of fuel going no faster then 55mph. was shocked @ 28.9 mpg. the next tank, I ran the posted speed limit (65-70) it jumped to 30 mpg. Go figure

[Evan]

When runing 75 out on the flats I'll get 38mpg on the '83. 5th gear/4000+rpm. Slower, and in the twisties, using 2nd-3rd- and maybe 4th, I'll get 50mpg. So yeah your mpg will get better, but who wants to do 55mph on the interstate.... 32mpg is still too low. Check the choke...

I know what Condor says is what your should expect. However, my 88VR seems to be a bit different. I often ride to my cottage which is about a 250 mille run - mostly on 4 lane divided highways. Over the past year, both before and after I did Skydoc's shim mod and replaced my diaphrams, my mileage on that run doesn't seem to be affected much by running speed. I am getting better mileage after the mods, but cruising at a higher speed (just under 75 to avoid tickets) just dosen't seem to affect my mileage much, or as much as other factors such as head wind.