Adjusting Choke Linkage

[V7Goose]

First let me say that I am not the originator of this information. While at Don's maintenance day, one of our members was running around with a pair of needle-nose pliers adjusting the carb linkage tabs on various bikes. I am very sorry that I do not remember who this was, as I was concentrating very hard on syncing carbs and trying to keep from wilting in the heat! I did hear enough about it while he was working on a bike next to me that I remembered to check my own bikes when I got home. Glad I did.

 

So let's get the real person identified here so he gets proper credit!

 

Background:

Our chokes are really just an enriching circuit that makes the bike run rich while the knob is pulled out. If you look under the tank at the choke knob, you can easily see the linkage and how it moves. In this first picture you can see that linkage on the left side of the bike, and just above the throttle spring you can see the tab the goes up to engage a brass plunger:

[ATTACH]18696[/ATTACH]

 

Here is a closeup of just that tab and plunger. You can clearly see how the metal tab is touching the inside shoulder of the plunger, forcing it all the way closed when the choke knob is pushed in. This is the correct position for the tab when the choke is closed:

[ATTACH]18697[/ATTACH]

 

As you begin to pull out the choke knob, those tabs move through that notch and begin to push against the head of the plungers to pull it out of the carb, activating the enriching circuit and making the engine run better when it is cold. The free play afforded by the notch probably just makes the bike less sensitive to slight position changes of the choke knob.

 

Those pictures were from my 07 RSV, and all four choke tabs looked fine. Now here is a picture of what I found on 3 of the four carbs on my 05 RSV:

[ATTACH]18695[/ATTACH]

 

Besides the fact that it is dirty and nasty, notice how the tab is touching the head of the plunger while the choke is supposed to be off. At the very least this is not ensuring the plunger is all the way in, and worse, it is probably actually preventing it from closing. In that case, the result could be poor fuel mileage, rough idling in the heat, fouled plugs, etc.

 

Those tabs are very soft metal, so if any of yours do not look right, just use a pair of needle-nose pliers to slightly bend the tab to rest up against the inside shoulder of the brass plunger when the choke knob is all the way in. If you have the Yamaha chrome carb covers on your bike, you will need to remove them to see all four tabs.

 

I do not yet know how this fix has affected my fuel mileage, but I will report back after I have had a chance to run a tank or two through it on the open road.

Goose

[Freebird]

I believe it was non other than the legendary Muffinman that was doing that. I can see where it would definitely cause problems. I got all excited about it and thought that maybe it could be the answer to the fuel mileage and fume problems that I had experienced but I checked mine and they are all as they should be. Oh well........

[cecdoo]

Yep it was muffinman, he was trying to see if it was causing B2dad's poor gas mileage, wonder if anyone noticed a big improvement in mileage? Craig

[Riderduke]

Yes the MUFFINMAN did this adjustment to my bike and Sledgehammer's We both noticed an increase in gas milage. Mine went from 30-31mpg to 33-36mpg. I also had a color tune before this adjustment and really didn't notice a mpg change till this adjustment. The color tune gave me a better responce to the throttle. This adjustment gave me better mpg and a little smoother idol at stop light and signs.

 

I'm sure Tim aka Sledgehammer will chime in

[wkboard]

Muffinman did mine also. 3 were ok, 1 was a tiny bit out. I didn't notice any mileage change, but I was fighting strong headwinds all the way home. I will be watching the mileage numbers now, to see if it changed.

Thanks to Muffinman for figureing it out, and fixing it!

Thanks to V7Goose for the post with excellent pictures!!!!!

[V7Goose]

OK, I have just burned my first tank of gas since adjusting the choke linkage on my 05 RSV "QuickSilver." Although just one tank is too soon to be absolutely certain, the results so far are VERY positive. I burned this tank around town and some local freeway riding. In those conditions, I'm pretty sure I never got better than 36 MPG. This tank came in at a solid 38 MPG. I'm looking forward to getting a full tank through it on the highway to see what I get.

Goose