Clicking carburettor

[MrDavo]

I asked this in my Z1A rebuild thread but as I’ve had no response yet, I thought it would be better to ask here.

My bank of carbs are as bought, already rebuilt and now fitted on the bike. Yesterday for the first time I fitted the throttle cables. As I open the throttle there is a noticeable ‘click’ from number one carb as the slide moves from the closed position. I have lubed the linkages and peered inside after removing the polished cover but I am none the wiser. I don’t want to have to remove the carbs again to dismantle one of them, but if it’s necessary I will have to. Maybe it won’t make a difference but I know that it isn’t right, and now is obviously the time to sort things out.

I can’t see anything catching in there, I did wonder about a bent needle being a possibility. Any ideas?

[zed1015]

Most likely something in the lifter mechanism.

[engz1b]

sounds like the bolt on the lifter is loose , ive had that before, will be able to tighten it whilst in place

[MrDavo]

Thanks for that, I’ll investigate and get back to you.

[MrDavo]

I tried tightening the spindle bolt, however it didn't make any difference, as the bolt screws into a threaded hole on its shaft. Here is a short video of the sticking in action, you will see the opening mechanism move but the slide doesn't, then it moves with an audible click to catch up the rest of the carbs.

https://youtu.be/dUR5wDwvdzg

Clearly not acceptable, slow speed running would be awful if left like this. It seems I was close with 'bent needle' but not quite.

I took the set of carbs off as one, then liberated the left hand pair as per the workshop manual. I then stripped #1 carb - the sticking still happened with the lifter mechanism removed, so the slide or needle then. Here the jet holder tube and the main jet defy gravity by sticking to the needle.



It turns out that the tube is slightly bent. You can't really see it in this photo but it is sightly deformed near the top and is ever so slightly 'S' shaped. I think its just enough to foul the needle and cause the drag.



Because of the taper I can't properly check the needle for straightness. I think its OK but for the sake of a few quid I'm changing it for peace of mind. CMS have one genuine tube and one needle in stock, so I've ordered them. Other carb parts seem to be OEM, I don't want to start mixing n parts from pattern 'rebuild kits' if I can help it. I used these with my CL450, in the end I only got that bike running right by binning all the aftermarket bits and using genuine OEM stuff, new or my old parts cleaned up.

[kev edwards]

That tube looks like it has taken a hell of a bashing, you can always try the needle in the other carb