HS6 dashpot problem

[Doherto]

Hi all, this is a very very silly one but one i have spent the last two hours on with no joy. I have twin HS6 su carbs on my 1968 240 which i have refurbished and refitted. The rebuilt engine is running well enough for now as i continue with the body and interior but she will not return to tickover from the accelerator pedal. I have increased the return spring pressure without any joy but then found that i could not raise the carb pistons with the actuators on the side on both carbs. I have removed the piston bell housing covers and the pistons both slide into the jet easily. When i put the housing covers back on there is a slight resistance to raise the pistons but by moving the covers around slightly i can get them to raise with the actuator and fall freely. HOWEVER as soon as i apply any downward pressure on the covers the piston movement caused by the actuator jams therefore replacing the mounting screws has the same effect. I have swapped housings, cleaned the inside of the covers and outside of the pistons, lubricated both surfaces but still have the same problem. I am at a loss as to how such a simple bit of mechanics is causing this problem. Hopefully someone will have had a similer problem and can help. Or should there be a gasket under each bell housing cover, i cannot see one on the exploded diagrams of the carbs but hopefuly there is something i have missed.

[steve_m]

Have a look at the diagram, it shows a bell housing gasket.

http://sucarb.co.uk/hs6-type-gasket-pack.html

[Doherto]

Steve, thank you for your quick reply, unfortunately as i suspected the gasket in the pack is for the float chamber. I have spoken to Burlen now and they confirm that there is not a gasket on the bell housing. They have suggested that it is proberbly the needle catching in the jet. I thought i had centered them when i rebuilt them but apparently they need to be centered with the dashpots on, which i suppose makes sence, so I fear i will have to take the carbs off and try again. Unless anyone has a magic suggestion.?

[PPV]

As you suggest, the problem could well be the need to centre the jets/needles. There is no gasket on the 'bell' housing. It is a machined fit and should not allow any wiggle before you screw it down. Also ensure you tighten the screws evenly when assembling.
Regards,

[Tintin]

This may help

http://sucarb.co.uk/technical-h-type-ca ... -servicing

[Doherto]

Thank you tintin the info was in line with the haynes and workshop manual. Took the carbs off this morning, reset as per instructions and refitted in just over two hours. Not bad but i do not look forward to doing this type of job when the rebuild is finished and the bonnet is in place !!!!! Engine running great or at least well enough now to allow me to move her to finish the rebuild. I think a visit to an expert to then do the final carb set will be in order though.