[Son of Magni]

This is the same problem I always had on my first 240. When I slow down to a stop I always have to kick the throttle to get it to come all the way back to idle. What's worse is driving at say 40mph in 3rd, if I want to speed up a little I keep pushing harder then it suddenly goes down far enough to get me to 50. I've cleaned the linkage with carb spray then lubed it with various things like bike chain oil or silicone spray. It seems like maybe it's best just clean with no lube.

So should it be lubed? If so, with what? Or leave it dry? Or do I just need to replace all the linkage???
SoM

 

[Unknown User]

If memory serves me correct there is an anti backfire valve on the manifold between the carbs, it's been so long since I've seen one. It is there to stop your linkage from "snapping closed" when you release the pedal, suposedly to gradually close the throttle preventing backfireing. It could be out of adjustment, sticking or just not working.

 

[john cross]

It can't be the anti B/F valve. This has nothing to do with the mechanical function, which is obviously fuked up. Somthing is very wrong here, and you should look at it. I once had a throttle return spring go, and that was scary. You should check that first. If they are in place, then there is no obvious explanation. Worse still, you bearings may be seizing. This is a potential safety hazard. Get it looked at! It can't be you anti B/F. All this device does is suck air in when you take your foot off. it will slow the deceleration, but there is nothing mechanical to it.

You should say more about the year of your car, the carb setup, etc. Or is it fuel-injected?

 

[Son of Magni]

It's a '72 with roundtops, the old one was a '72. The antibackfire thing, I think it was called a dashpot, was removed on both cars. When I take my foot off the gas I want to slow down.

On the '71, and this was around 1982, it once stuck down when I was on snow so I had to hit the clutch to get control of the car. As I reached for the key, I saw the tach point straight down, 11,000 rpm? Then the engine quit and the tach rotated all the way back around. The reason the engine quit? The rubbing block broke off the points, everything else was fine.
SoM

 

[71240L28]

Another thing to check . . .

With the car off, remove the dashpots, push the carb piston(s) up and see if they drop back down quickly and clunk. If they hang, the needle may be hitting the side of the jet tube. This can be fixed by loosening the jet tube with the piston/needle in place, then twirling the jet tube while tightening it back up.

 

[Unknown User]

My mistake: correction

What I was refering to as the antbackfire valve is the Deceleration control and high altitude corrector. I had this go bad on me and it caused the problem you are describing. 20 years ago, my mind is going. I've had Webbers so long I don't remember most of this stuff!

 

[Son of Magni]

Well, these are all really good thoughts but I've already checked these things. There's no emision controls left in the car, all there is is the rods and springs. Is everyone running the linkage dry and I'm making the mistake of trying to lube it or what?
SoM

 

[71240L28]

rarely/never lubed

and I've never had that problem. But I can't imagine lubricating your throttle linkage could cause sticking. Can you cause this problem sitting still in your driveway? If so, try disconnecting your linkage at the firewall. If that clears it up, the pedal or the rod going through the firewall is binding. If not, try disconnecting at the carbs, etc. Maybe this way you can isolate the problem. Keep trying because you don't want a stuck throttle!

Good Luck & let us know what you find