Choke

[Oggers]

Folks

76 400/4 running and handling well. One minor issue - well hopefully minor. Choke lever on the nearside is connected to the (common) choke flaps by a length of bent rod with a collar and grub screw. The issue is that the choke flap spring works to pull the choke flaps closed. When the choke lever is actuated to the open position - fully forward and  normal running - there does not appear to be adequate sticktion - for want of better words - to hold the choke flaps open against the spring. What happens is the choke closes itself when the bike is ridden, and will not stay in the open position. Result is a rich running bike and 3000 rpm on tickover!  - unless I push the choke lever forward again.

As an aside- if I disconnect the rod from the choke flaps, the lever moves freely and fully forward

Am I missing something blindingly obvious here?   

[Nurse Julie]

Have you got the little ball bearing in situ so the lever 'clicks' locked 🤔

[Oggers]

It doesn't "click"  when lever is pushed forward into the open position, I assume it is supposed to?

[Nurse Julie]

It doesn't "click"  when lever is pushed forward into the open position, I assume it is supposed to?

Yes, when you push the lever into the down position (ie, when engine fully warmed up) there is a definite 'click' where the minute ball bearing locates and holds the lever in that position to stop it moving from vibration.

[Nurse Julie]

It's part of #91 but the ball bearing and spring don't have part numbers 😁😁😁

The choke lever on no.1 carb has a very, very small ball held by a spring. The spring pushes the ball into an indent when the choke is off.

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[Deano400]

Not a great picture but this is what Julie is pointing to.

[Oggers]

Nurse - yes quite right, had a look. I think what has happenned is that I stuck the minute ball bearing in the recess without the spring - as I seem to have that minute spring right in front of me! I'm a fool I know! Poking about with a bit of wire, i thing the ball bearing is still in there.  Tried blue tack on the end of a wire, tried araldite, but as I greased everything it just won't adhere and pull it out.

The only thing I can think of is drill a small hole from the other side and poke it out with a bit of stiff wire!

Any other clues gratefully apppreciated!

[Nurse Julie]

Nurse - yes quite right, had a look. I think what has happenned is that I stuck the minute ball bearing in the recess without the spring - as I seem to have that minute spring right in front of me! I'm a fool I know! Poking about with a bit of wire, i thing the ball bearing is still in there.  Tried blue tack on the end of a wire, tried araldite, but as I greased everything it just won't adhere and pull it out.

The only thing I can think of is drill a small hole from the other side and poke it out with a bit of stiff wire!

Any other clues gratefully apppreciated!

However you go about it, its an awkward little fix but at least its nothing major and once the spring and ball bearing are in situ, hopefully that should resolve the problem you are having.

[Oggers]

Awkward is right! I am not tipping the bike on its side to get the ball out!

Thanks for the confirmation in any case.

[Oggie400F]

Why not try blasting it out with the small red tube from the WD40 down the hole?
Just make sure you have a suitable tray in place to catch it if it flies out.

[sye]

Nail, magnet, job done 👍

[Oggers]

Tried a small magnet, blu-tack, superglue on end of nail, teasing out with a thin wire. All no good, mainly because the ball is covered in grease - which keeps it in the recess. However, I bit the bullet. and drilled a very small hole from the other side and poked it out with the drill bit. Reassembled  - with the spring this time! - and I now have a click and a choke which stays open. Hurrah. You cannot see the hole as it obscured by the choke lever - very small anyways

All of this was a huge slice of luck. I found the wee spring on the garage floor last week, wondered where it came from, and kept it. Now I know!

Many thanks for all the help

[SteveD CB500K0]

I found the wee spring on the garage floor last week, wondered where it came from, and kept it.

Do you do the lottery?

[Oggers]

Ha ha - no lottery, but a very very lucky find for sure. Wonder if there are spares for it? Bike definitely smoother now it is not running slightly rich!

[Lobo]

.... I’m left wondering what design criteria would spring-load a choke to fully closed??  There is ‘potential’ for an engine failure here - possibly dangerous if on a motorways etc.