Update on Improved Gas Milage After Mods!

[Dragonslayer]

Hey Bob,

You did just fine. The set of needles in my 87'VR were roll stamped with a part number and I was not able to remove the nylon spacer without removing the cir-clip. I did not have any extra needles or washers so I took the needle to the hardware store and found that #6 stainless steel washer was pretty darn close to the metric washers on the topside of the cir-clip. The only thing I would suggest to you now is to keep a eye on your plugs and make sure they tan up a bit after a few tanks. If not, add a washer and all should be well. The washers I got are .025 thick and I was able to "kiss" another .005 off of them with an "India Stone" for the final adjustment that got me to 47MPG and still tanned the plug. The combo of the new Diaphragms, slider shim mod, crankcase vent mod, and a really good Carb. Sync. splitting the difference between idle and 3500 RPMs did the trick. I am going to Freebird's Maint. Day and will be traveling almost 1000 miles round trip and hope to really document the milage at that time.

I hope this clears this up for you,

Earl

I'm still wondering how to gain that 20 mpg difference between your results and mine?

[GeorgeS]

Have you done a Compression Check on that Engine ??

 

Also, on your next run, Pull into shop, immediatly pull the Plugs,

Post a close up of them. I would like to see what they look like.

[Dragonslayer]

Have you done a Compression Check on that Engine ??

 

Also, on your next run, Pull into shop, immediatly pull the Plugs,

Post a close up of them. I would like to see what they look like.

will do next time I come in from a high speed run

[jasonm.]

Hey Dave,

This project started when I put a K&N Air Filter in my 87'VR and the increased air flow started vacuuming oil vapor into the air box and contaminating the new K&N Air Filter I had just installed. Besides the benefit of no more oil in the airbox the other benefits were the Carbs. got a nice clean shot of air with no oil mist in it, which improved performance noticeably and if I keep out of the throttle, I got a gas mileage increase in the 2 to 3 MPG range.( *NOTE* Be prepared to catch he!! from some "tree huggers" over this mod!)

I have attached pics below, If you need more information, just ask!

Earl

Typically but not always...excess oil in airbox is due to worn valve guides or piston rings or other items near the combustion chamber allowing the pressures to escape that are meant to be harnessed during combustion. I have done may high speed rides since getting my '87 on the road and looked in the airbox...no puddles or oil on my K&N.

[Schlepporello]

Ya reckon you could grace us with a part number on the crankcase filter?

[CrazyHorse]

I did the mod with lowering the needles using 2 brass washers on the bottom of the c clip and 2 on top while removing the plastic spacer. I used the original 1983 needles which have 5 adjustment levels compared to my 1990 non-adjustable needle. I set the needles originally to the highest setting mileage was terrible at 25 mpg smelled rich and stumbled off the line. I then lowered them to the lowest set position #5 I'll call it and used the 2 brass washers on bottom 2 above the cclip to make the needle stay in position. Mileage is 41-45 mpg (used to be 37mpg) if I take it easy and now seems to have more power if I want to crank it (as compared to the original 1990 needles). The 1983 needles have a much more aggressive taper to them then 1990 needles for high speed runs. Ill take a picture comparing the 2.

[concord006]

I was looking at the Needle jet mod to lower the needle because of poor mileage. All plugs running rich and the smell of gas out the exhaust and splatting on the shop floor. My main needle have six spots to put the cir clip. Is this original? I just lower the needle one notch and my plugs turned fairly white after about 60 miles. Needless to say a little worried. So if I leave the setting can I use the Idle mixture screw to richen the mixture or is that in a different rpm range? Oh I compared the needle you guys are showing on here with the one cir clip spot and it was pretty much the same place as mine 3rd from the top. I hope someone could shed some light on this for me. Thanks Brent.

[skydoc_17]

Hey Brent,

The MKI VR's (mostly 1983 but some 1984 models) Had the adjustable main jet needles. What Yamaha discovered was that many owners adjusted the main jet needle "way to lean" and this caused engine problems. So Yamaha removed the adjustable needles and went to the non-adjustable main jet needles. What you need to understand here is that when a bike runs "rich" it does very little damage to the engine from a warranty standpoint, but it does provide income to the dealership in the sale of spark plugs, Carb. Syncs. and tune up parts in general. It is a "win,Win," for the dealers.

Because we run unleaded gas in our engines, it can be hard to "read" a spark plug if it has only been in a motor for a short time. The adjustment of the "Idle mixture screw" is going to effect just that, Idle to about 1800 RPMS. Besides, it adjusts air flow, not fuel flow.

Set all 4 Idle Mixture Screws at 21/2 turns from bottom. Then Adjust the clip on the main jet needle until you see low to mid 40's on your MPG. At that point you have done about all that you can do with this adjustment. For the owners with the non-adjustable main jet needles, I now machine a replacement nylon spacer which takes the place of the stock nylon spacer, This new nylon spacer doesn't add additional weight to the end of the Diaphragm Slider assembly like the steel washers do, which could cause the Diaphragm slider to "drag" (not float as freely because of the extra weight).

If you have questions or are interested in parts, please feel free to contact me.

Earl

[Craigs87]

I did the mods on my 87'VR and the gas milage has dropped.

1) All 4 Carb. Diaphragms replaced

2) Needle Shim Mod (Removed Nylon spacer and replaced with S.S. washers, .050 thinner than Nylon spacer)

3) Crankcase Vent Mod

4) Carb. Sync (purchased sync gage manifold)

5) Adjusted Mixture to 3 turns from bottom.

6) New Plugs

7) New Wires

8) Aftermarket TCI

The bike starts great, runs good, Idle is set at 1k, no more exhaust popping after I adjusted mixture from 2.5 to 3 turns from bottom.

Before the mods I was getting 38 MPG now after the last 4 tankfuls of gas, I have been getting 33 MPG.

No change in riding style and over the same daily route to and from work.

I checked the carb sync after 300 miles and all was still good. I have put 500 miles on the bike since the mods.

Any ideas where I went wrong?

 

My TCI Settings:

RPM_ADV 1300 1700 2100 2600 3100 3600 4200 4800 5500 6000

5 10 16 19 25 30 35 36 37 37

 

When I changed plugs I went from (NIPPONDENSO) X24EPR-U9 to (NGK) DPR8EA-9 with the gap set at .035"

 

Craig

Edited November 14, 2011 by Craigs87
updated info

[GaryZ]

Doc,

I have read a couple of different CV carb articles that say there are three circuits (with jets) in these VR carbs; low, mid and high. One of these articles came off of a Vmax site. I have attached one article that I saved.

 

Your very good discussion seems to only address the low and high circuits.

What about the mid?

[utadventure]

Craig-

 

Looks like you did a lot of work!

 

I did the needle mod only on my '86. At first it did nothing but I notice a difference the next spring. What happened during the winter is anybodies guess.

 

Here's my thought: Start checking each mod individually. Put the nylon washers (or equivilent) back on the sliders and see if your mileage changes, up or down.

 

The new TCI may have had the biggest effect. Next, put the original back in, if possible.

 

Etc, etc, etc and see if you find what may the big change.

 

Could be a lot of work but when you find what had the big impact you can do research to find the right answer.

 

FYI, I did adjust my mixture screws and I don't think they are more than 2.25 from the bottom.

 

Dave

[bkuhr]

I did the mods on my 87'VR and the gas milage has dropped.

1) All 4 Carb. Diaphragms replaced

2) Needle Shim Mod (Removed Nylon spacer and replaced with S.S. washers, .050 thinner than Nylon spacer)

3) Crankcase Vent Mod

4) Carb. Sync (purchased sync gage manifold)

5) Adjusted Mixture to 3 turns from bottom.

6) New Plugs

7) New Wires

8) Aftermarket TCI

The bike starts great, runs good, Idle is set at 1k, no more exhaust popping after I adjusted mixture from 2.5 to 3 turns from bottom.

Before the mods I was getting 38 MPG now after the last 4 tankfuls of gas, I have been getting 33 MPG.

No change in riding style and over the same daily route to and from work.

I checked the carb sync after 300 miles and all was still good. I have put 500 miles on the bike since the mods.

Any ideas where I went wrong?

 

My TCI Settings:

RPM_ADV 1300 1700 2100 2600 3100 3600 4200 4800 5500 6000

5 10 16 19 25 30 35 36 37 37

 

When I changed plugs I went from (NIPPONDENSO) X24EPR-U9 to (NGK) DPR8EA-9 with the gap set at .035"

 

Craig

You are listing a fixed, 2d advance/rpm. Are you not using any kind of throttle position input(MAP or TPS)for a 3d advance curve? I have been playing with an actual TPS where most here with ingitek TCI are using a MAP sensor, but in any case my advance tops out a whole lot faster than yours. Suspect it feels like bogging a little above 3000 rpm.

Attached copy of 3d curve I am currently using, but I messed up my last mileage check due to fuel leak-stuck float, but I was running high 30's.

[CrazyHorse]

Craig-

 

Looks like you did a lot of work!

 

I did the needle mod only on my '86. At first it did nothing but I notice a difference the next spring. What happened during the winter is anybodies guess.

 

Here's my thought: Start checking each mod individually. Put the nylon washers (or equivilent) back on the sliders and see if your mileage changes, up or down.

 

The new TCI may have had the biggest effect. Next, put the original back in, if possible.

 

Etc, etc, etc and see if you find what may the big change.

 

Could be a lot of work but when you find what had the big impact you can do research to find the right answer.

 

FYI, I did adjust my mixture screws and I don't think they are more than 2.25 from the bottom.

 

Dave

 

I have a new ignitek tci my mileage is worse also. Getting 35-36 now used to be 40. Im going to have to play with settings. Bike runs good though.

[Craigs87]

I mistakenly listed the change of TCI as number 8 when in fact it was the first change and the MPG did not change. The MPG reduction was after the 1-7 items where done over a weekend.

 

I also neglected to point out that I am using the Igitech TCI without a MAP sensor or TPS.

 

Looking over the attachment Gary posted I realized that I was enriching the mix and not leaning it, so I will adjust the mixture back to 2.25 turns first as Dave has his set and deal with the exhaust popping to see if that makes a positive change in MPG.

 

After that I will take Brian's TCI settings and start playing more with those to see if I get any positive change. I am not noticing any bogging down.

 

Addition of the MAP sensor will be the follow on change after these adjustments.

 

Thanks for the ideas, I had a feeling I did something wrong.

 

Craig

Edited November 16, 2011 by Craigs87
spelling

[Yamamike]

Typically but not always...excess oil in airbox is due to worn valve guides or piston rings or other items near the combustion chamber allowing the pressures to escape that are meant to be harnessed during combustion. I have done may high speed rides since getting my '87 on the road and looked in the airbox...no puddles or oil on my K&N.

 

I think I read a post mentioning that crankcase oil level above the half mark will also cause this to happen.

[Craigs87]

Before I did the mods I had no indication of oil in the air box. But a compression check is most likely in order now. It will at least give me a baseline for future issues.

 

Craig