Dash pot piston unscrews during driving.

[Tr4aJim]

Ok this is weird. Recently, after a drive, the dashpot piston unscrews itself from the forward carb (HS6). After I get home, I routinely open the bonnet to disconnect the battery and to allow the heat to escape the engine compartment (and to be honest to check for leaks). After the last three drives, of roughly an hour each, I’ve found the forward dashpot piston sitting loose, with the cap about an inch proud of the dashpot (apparently the piston is riding on top of the oil). The first time it happened I assumed I hadn’t tightened it sufficiently, so I gave it an extra twist. After the second time, I gave it a good yank. Now I’m puzzled. The washer is in place under the cap. The cap on the rear most carb behaves itself. What’s also strange is I don’t feel any change in engine performance as a result. Any ideas?

Thanks

Jim

[TR NIALL]

37 minutes ago, Tr4aJim said:

Ok this is weird. Recently, after a drive, the dashpot piston unscrews itself from the forward carb (HS6). After I get home, I routinely open the bonnet to disconnect the battery and to allow the heat to escape the engine compartment (and to be honest to check for leaks). After the last three drives, of roughly an hour each, I’ve found the forward dashpot piston sitting loose, with the cap about an inch proud of the dashpot (apparently the piston is riding on top of the oil). The first time it happened I assumed I hadn’t tightened it sufficiently, so I gave it an extra twist. After the second time, I gave it a good yank. Now I’m puzzled. The washer is in place under the cap. The cap on the rear most carb behaves itself. What’s also strange is I don’t feel any change in engine performance as a result. Any ideas?

Thanks

Jim

If your talking about the Black Plastic Plunger swop them around and see if it still happens as I think the Threads are worn on one,I had the same problem some years ago.

[Tr4aJim]

Sorry, I meant the damper piston. I will swap them and see what happens. Regarding the treads, the dampers I have use a black plastic cap, so I guess they can wear/distort over time. If I need to replace them, would brass ones be better?

Jim

[TR NIALL]

12 minutes ago, Tr4aJim said:

Sorry, I meant the damper piston. I will swap them and see what happens. Regarding the treads, the dampers I have use a black plastic cap, so I guess they can wear/distort over time. If I need to replace them, would brass ones be better?

Jim

Not sure if the Brass ones would be any better but I think the cause of my one been worn was that somebody had cross threaded it at some stage.

[BlueTR3A-5EKT]

Austin Morris had this issue on the Metro Turbo so fitted a retainer strap to the dash pot and damper.    Requires a groove cutting in the dash pot outer surface to seat the retainer.   Have fun sourcing one.

 

[Ralph Whitaker]

Cut the finger off a rubber glove and stretch over the damper knob and top of the carb. It will stop it undoing. May not look good but will work.

Ralph

[Tr4aJim]

I found some rubber O rings almost the same thickness as the fiber washers, so I put those on the pistons. I’ll see if that helps.
Jim

[Andy Moltu]

Threads must be worn as they shouldn't unwind that easily.

[BlueTR3A-5EKT]

On 8/31/2023 at 11:25 AM, Ralph Whitaker said:

Cut the finger off a rubber glove and stretch over the damper knob and top of the carb. It will stop it undoing. May not look good but will work.

Ralph

But be sure not to block the vent hole in the top of the damper cap

[Tr4aJim]

Drove around a bit over our Labor Day long weekend, and so far the dampers are behaving with those O rings in place instead of fiber washers.

Jim