Diaphragms, shim washers and fuel mileage

[lonestarmedic]

So, last fall I changed the carb. diaphragms out in the 86. Found one with a slight crimp on the edge but no holes or problems. It was more of a preventative measure. Did a carb synch and set the idle circuits using the idle rpm drop method. Bike felt smooth and good power. However, my fuel mileage dropped from 40 commuting to 37. i run about 60-70 miles a day from work to home. The measured mpg is cold start with choke and all speeds. I could smell the exhaust as being a bit rich. Tried adjusting the idle screws to no avail. Fast forward to maintenence day. I have a set of needle shim washers and a color tune with me. MikeZ and I changed out the washers and set the synch again. It looked pretty good. I could also tell that there was a difference by the choke lever settings. The colortune needs modification to work on the venture. So, did not touch the idle settings. On the way back to San Antonio I got 37 heading into a wind. I used almost a gallon less fuel than Mike did on his 1989. Now, it had more luggage on board and did have a bit of an afterfire. Next week it was back to commuting to work. Checked several tanks of fuel and found I am up to 41mpg! And the rich smell at idle is gone. So my suspicion is that the replacement diaphragm are not only a bit stiffer than the originals, but possibly a bit thicker. Plug color is good. Next stop is figuring out a good way to use the colortune on the V-4.

 

JB

[skydoc_17]

Hey JB,

I can honestly say that it took a few thousand miles for my 87'VR to "Break In" the Carb. Diaphragms after I changed them. I was wondering if you used the Nylon Needle Shims, or did you replace the stock Nylon Needle Shims with S.S. washers? I have seen in the past the combination of a new set of after market Carb. Diaphragms, and the weight of S.S. washers replacing the Needle Shims on the Carb. Sliders really slows down the slider action, which makes you twist the throttle all that much harder, resulting in poor gas mileage. As those Diaphragms loosen up, you should see another mile or two better MPG's on your scoot. As far as the Color Tune Goes, I know many people that have them, but because the spark plug hole is so deep in the well of the cylinder head, that tool will most likely spend most of it's life in the bottom of your tool box! I am ALWAYS impressed when a VR owner takes the time to really "Fine Tune" their scoot. Because of the many mods on my 87'VR, I have "fiddled" with my Carbs. a hundred times. Not many have the patience for that. I commend you for your patience, and the resulting gas mileage improvement! Just in case someone else would like better gas mileage yourself:

http://www.venturerider.org/classifieds/showproduct.php?product=3770&title=first-gen1983-to-1993-vr-needle-shim-mod-kit-21&cat=22

Earl

[lonestarmedic]

Well Earl- you sent me 4 white washers. Hope they were nylon not stainless!!

 

JB

[skydoc_17]

Hey JB,

I screwed up, I sent you the "Good Nylon" shims by mistake! I meant to send you a set of rusty old cast iron ones I had laying around.

I must be getting old!

You did good JB, give those Diaphragms a bit more break in time, and you might even see 45 MPG when the dust settles. Which reminds me, make sure you have a clean air filter,

a clogged air filter will slow the wind up on these motors. I wish I could get 5 extra MPG on my truck!

Congrats on a job well done!

Earl

[IH Truck Guy]

Earl,when did you start using the nylon shims?????????

IIRC, when you did mine a couple of years ago,we used the stainless steel shims.....

Looks like I have an upgrade to do.....lol

[skydoc_17]

Hey Dan,

A few months ago, I got a Blue 87 Standard as a parts bike here at the shop. Every time I look at that bike, I think of the fun time we had a few years ago. I hope the road is treating you well, my friend. Please send my best regards to your lovely wife, and Jean says "Hey". This link will take you to the NEW Needle Shim Mod I offer now. The new shims are Nylon, are lighter, and are a refinement of the original S.S. shims that were installed on the Main Jet Needle years ago. I custom machine these nylon shims on my lathe. Here's the link:

http://www.venturerider.org/classifieds/showproduct.php?product=3770&title=first-gen1983-to-1993-vr-needle-shim-mod-kit-21&cat=22

 

I sure would love to see you at Don's this year, It always brings back fond memories.

Earl

[Flyinfool]

Speaking of Dons MD.

Is this shim mod and diaphragms a realistic MD job?

I have the diaphragms but still will need the shim kit.

Are there gaskets or other items that will be needed as part of this, or as something else that should be done while in there.

Carbs are blue smoke and mirrors to me. Hate them.

[lonestarmedic]

Earl- I have a K and N installed. So, I washed it and dried it out. Then to be sure it caught all of the dust I used 90 weight to oil it. That red stuff looked too thin and wimpy. The diaphragms have over 5000 miles on them since I installed them so I think they are limbered up. I will probably check my valve shims this fall when I rip the tupperware off for a repaint. I need to seal my valve covers-- again. I will have around 85,000 miles on the original factory shim job. My plugs are from last year. Might put in the new set to see what happens.

 

JB

 

P.S. the cast washers are good for slowing slide response to give 2nd Gens a chance to catch up.

[Prairiehammer]

90 weight gear oil?!

I hope you are kidding. If not kidding, then I suggest that the K&N is not breathing as designed and may be effectively partially plugged, causing a rich condition. The "red stuff" is the only stuff you should be oiling your K&N with.

[twigg]

90 weight gear oil?!

I hope you are kidding. If not kidding, then I suggest that the K&N is not breathing as designed and may be effectively partially plugged, causing a rich condition. The "red stuff" is the only stuff you should be oiling your K&N with.

 

I put mine in a plastic bag .... keeps it nice and clean but starting can be troublesome

[MikeZ06Allen]

On the way back to San Antonio I got 37 heading into a wind. I used almost a gallon less fuel than Mike did on his 1989. Now, it had more luggage on board and did have a bit of an afterfire.

JB

 

And I had folding chairs acting as "air foils"...no wait that was on the way out. Note to all that haul chairs and such, putting them crossways on the luggage rack is "not" a good idea.

 

Flyinfool,

 

The shims do not require any extra gaskets or "magic" as I like to call it. Simply remove your carb diaphragm covers, then the slider assembly. Earl provides very good instructions with the kit. Heck they were so good even I could do the mod!!!! All in all it will take about thirty minutes to do the mod. So yes a very easy MD task.

[greg_in_london]

SkyDoc - I bought some of this off you before, but they disappeared down that big crack in the settee (or somewhere similar) before I could use them, so fitted washers instead. I'd still rather have the nylon washers, so I've just ordered another set. Let me know if you need more for the postage.

 

Greg

[KIC]

Just ordered 2 sets... hopefully it will help with the gas smell my 89 has developed and since the 87 is apart..why not ? Sounds fast and easy for a small amount of $$$.

[lonestarmedic]

Mike- As I recall, the chairs gave you about 25mpg. Wpould not have thought 2 fairly round objects like folding camp chairs in bags could do that. But, when he turned them in-line to the bike it was worth almost 5mpg!! Just imagine if he would have left them unfolded.

 

JB

[greg_in_london]

If you're getting a strong smell of petrol, have you ever checked the o-rings on the emulsion tubes. It's hard to be sure, but I'd almost swear I had been able to see petrol flowing down the carb wall from the emulsion tue/needle jet before I replaced them. Downside is that you have pull the cars and dismantle to get at them