9 replies to this topic

[benjamini1997]

1989 Mayfair (not sure on what carb it has/should have) is it normal for it to be almost stuck down and hard to lift the piston when putting your hand down the back? Trying to problem solve and not sure if this is or isn't a problem

[nicklouse]

yes there should be resistance.

[benjamini1997]

It has a distinctive click as I pull it up from being set right down, that normal?

[David128]

Hi 

 

A slight resistance is normal. Can you lift the piston all the way to the top and let it drop you should hear a click then. as it drops right down to its seat, if its sticking it will need cleaning with nothing more abrasive than metal polish. 

[benjamini1997]

That's what I mean! When it seats! When I then go to lift it, it feels stuck in place and takes a big pull to get it to lift, I'll clean it now

[Alex_B]

Strip it and give it a really good clean, I had an issue with my carb piston sticking, started off not wanting to idle in traffic and then got to the point where the piston stuck up the bore and meant the mixture was far too lean and wouldnt start. 

There should be resistance that feels like a damper (as there is a damper in there) but should move smoothly and freely so clean it up and inspect, when reassembled check how it feels and go from there. 

[benjamini1997]

Thank you for that, by cleaning up how do I go about that? Just an abrasive pad around all of it?

[Spitz]

You should pull your dashpot cover off.  Have a look for crud, and clean it anyway.  Also make sure your needle isn't bent or worn from not being able to move properly...it should be spring loaded.

Also, there may be a lift pin on one of the sides of the carb that can be used to lift the piston slightly ( not all carbs have this feature ).  You can also lift the piston with your finger, as you have been, with the engine running. There should not be too much resistance

Edited by Spitz, 16 December 2015 - 07:09 PM.

[David128]

as previous post clean with metal polish like silvo or brasso

[Cooperman]

You should be able to lift it with your finger with only slight resistance. When you let it go it should fall smoothly and there should be a 'click' as it stops on its seat.

The needle should not interfere with this operation and it must have oil in the dashpot.

As David says above, clean the piston and inside face of the cover with a good metal polish and, if necessary, 1200 wet & dry with the polish.

It MUST rise & fall smoothly.