vm26 mystery spring

[gwyon]

I've got stock Mikuni VM26 carburetors on my 1978 GS750. I washed the carbs and the carb rack in Simple Green, and I found a spring in the cleaning bucket. It's 6.25 mm o.d. and about 10.30 mm long, very stiff. The ends of the spring are ground flat. One end is shiny, the other end is a bit corroded. The spring looks like it belongs on the carb rack somewhere, but (I think) all the carb rack springs are present and accounted for. I've looked at an exploded view of VM26 carbs, as well as the list of parts, and I don't see this spring listed. There are three springs located at the center of the carb rack where the throttle cables connect. All three are in place. I also have the choke lever tension spring and the big throttle return spring. I'm not sure where this spring came from.
NB -- I also washed the bike's airbox in the bucket, as well as the parts from a spare GS750 front fork. Nothing else.0925181540a.jpg

[allojohn]

How about the idle adjuster screw, that has a stiff spring on it.
63 on the parts fiche

[gwyon]

Here's a photo with the three springs at the center of the carb rack. Idle adjuster spring is in place.0925181603a.jpg

[Big T]

Air mixture screw spring from a carb?

[gwyon]

Nope. Air pilot screw springs are accounted for. This spring looks like it would sit inside a cylindrical bore somewhere on the carb rack or somewhere else. I thought it might be part of a throttle stop screw assembly, but I have those springs in place. I appreciate all ideas. Thanks.

[Steve]

It's quite possible that somebody has worked on the carbs before. In the process, they lost a spring. Since they couldn't find it, they got another one and went riding. Now that you have cleaned the carbs and moved them into a few different positions in the process of cleaning them, the spring has become dislodged from its hiding place.

Of course, this is just wild speculation, because that sort of thing NEVER happens to ANYONE.

.

[Jhurt]

This?

[gwyon]

Jhurt -- Nope, I've got that spring in its place. I thought about that spring too, because it's close in size and sits inside a bore. I took it out and compared the two springs. It's a bit wider and longer than the mystery spring. But thank you for thinking about this.

Steve -- I bought the bike in autumn 2015, a basket case. I assembled these carbs from a box of two sets of VM26s. I examined every part with a magnifying glass, checking jet sizes and carb body numbers, needle positions, etc.
But maybe you're right -- maybe a spring fell out of something else recently and lodged itself among the carbs. I can't imagine where it could have come from, but it's too big to be a pilot screw spring, and I can't find a place for it on the rack.
Thanks for helping.

[The1970's]

How about the spring that holds tension on the choke lever?

[Nessism]

That screw looks like the one on the gang plate that puts tension on a lever arm in the cable holder bracket.

carb spring.jpg

[gwyon]

Nope and nope. All those springs are in place. I put the carbs back on today. Runs great. I guess I'll never know where that mystery spring came from. Thanks to everyone for helping.

[Himble]

Mount it on a small piece of stained oregon, and label it "The Spring That Never Came Home".

[KEITH KRAUSE]

Looks like the spring for the throttle pulley stop screw. Only a few loops and the loops looks like they've been pulled apart somewhat. No other spring on those carbs look like that.
Steve is right in thinking a previous owner lost the spring and it somehow got stuck somewhere.
That screw should be adjusted so when the slides are fully open, the bottom of the slides (front of the slide) should be 0.5 to 1mm above the main bore.