daverclasper Posted December 17, 2016 Report Share Posted December 17, 2016 Hi folks Have done this before quite a few times fairly easily. Have removed the diaphragm and refitted it with tabs correctly located. Now having real trouble tightening the top cover (diagonally opposite sides a little at a time) without the piston sticking (one screw seems more rogue than the others and even the slightest turn will cause this). Any clues would be great thanks Cheers, Dave Link to comment Share on other sites More sharing options...
Guest Posted December 17, 2016 Report Share Posted December 17, 2016 Dave. Have you replaced the top cover in exactly the same position prior to removing it and have you replaced the damper units in to their correct dashpot - basically have you done everything EXACTLY as to how it was before commencing work ?? It may even be as simple as a piece of grit preventing the pot to sit square or perhaps the rogue screw has carved its own thread in to the body - may be worth swapping the screws around and trying different holes. Just one of the above incorrectly fitted can produce a problem. It's all I can think of at the moment. Regards. Richard. Link to comment Share on other sites More sharing options...
dave.vitesse Posted December 18, 2016 Report Share Posted December 18, 2016 Just a thought, have you re-centred the jet. Dave Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2016 Report Share Posted December 18, 2016 yes undo the big nut on the jet holder 1/2 turn n give is a light tap with a spanner , make sure the piston is at its lowest point re nip the jet holder nut and then see if the problem persists if the piston slides easy in the top cover when its off with no sticking then jet centralising is most likely . Pete Link to comment Share on other sites More sharing options...
daverclasper Posted December 18, 2016 Author Report Share Posted December 18, 2016 Hi and thanks a lot for getting back The top cover is in correct and it's usual position. The jet assembly not fitted yet. The piston moves freely in the top cover and carb body. The problem appears to be a super sensitivity when doing the screws up. Pushing the piston up while doing alternating (1/8 turns) of screws and it will often bind. Backing screw back and tweaking others, then screwing again and I have finally got the piston to drop, though it is slow (compared to other carb) and doesn't make the reassuring noise when it contacts the bridge. Not sure if I can successfully center (my brand new) jet and needle while like this and also carb may not function properly. Cheers, Dave Link to comment Share on other sites More sharing options...
dave.vitesse Posted December 18, 2016 Report Share Posted December 18, 2016 Sounds like it may be a problem with the replacement diagram and not with anything you are doing. Dave Link to comment Share on other sites More sharing options...
daverclasper Posted December 18, 2016 Author Report Share Posted December 18, 2016 Hi. It's the original diaphragm (another story why I removed it), though looking back, I fitted the inner tab of diaphragm correctly in line, though there wasn't (to me) an obvious way to locate the inner edge centrally, so did it by eye. This could maybe result in the top cap bore being a bit to one side when the outer edge fits into the carb body?. Cheers, Dave Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2016 Report Share Posted December 18, 2016 Daves on a good point and with no needle fitted ......... some diaphragms are like a thick rubber not a film fimsy as they should be They should be very flexible and thin , the thick versions buckle up and resist a smooth drop With no needle fitted there is nothing to make contact , if the piston slides in the top cover then It should when screwed down, try it with the diaphragm removed there is a definite recess in the piston and casing to locate the lugs on the outer rim and the inner hole pete 1 Link to comment Share on other sites More sharing options...
dougbgt6 Posted December 18, 2016 Report Share Posted December 18, 2016 Laying it on a bit thin there Pete! Condoms are film flimsy, diaphragms are a bit more..... sturdy...............if memory serves. Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 19, 2016 Report Share Posted December 19, 2016 Doug, on that I can only surmise the thick ones were made from out dated dutch cap for an elephant I cant see what can affect the piston slide by tightening the screws in the cap , its not going to distort they are not graded or selective fits , mass produced and thrown together out of racks and bins unless something has happened in the past to distort the cover or bend the slide but it slides freely untiil dave nips the screws, , theres no needle to jam, just the spring and diaphragm pete Link to comment Share on other sites More sharing options...
dave.vitesse Posted December 19, 2016 Report Share Posted December 19, 2016 Sounds like the diaphragm is distorted. I would fit a new one. Dave Link to comment Share on other sites More sharing options...
Last_Vitesse Posted December 20, 2016 Report Share Posted December 20, 2016 Having just gone through a similar process, one of my carbs started sticking open on my vitesse. I bit the bullet and bought some new Diaphragm - Hydrin Based - 150 Type.( Bio fuel resistant) They are a much better fit and are thinner, than parts I have bought from other suppliers. http://zenithcarb.co.uk/cd-diaphragms/diaphragm-hydrin-based-150-types.html certainly worked for me . Regards Mike Link to comment Share on other sites More sharing options...
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