Probably been asked a million times before.......

[PatM]

Just skimming this thread and I thought valves - clearances, i mean. That causes a 400/4 not to start if they are too LOOSE

On the DSS exhaust- mine was a git to fit and I ended up grinding some of the collets down to get it to bed into the head. All ok now for 2 years- i just need to mark them if i have to take it off again. Cheaper than an OEM and most don't spot the joints.

[Laverda Dave]

This bike is turning into a nightmare!  Another long afternoon spent with the carbs apart for the 4th time, floats checked, all correct, O rings all fine, jets not blocked, pilot drillings clear. I put the carbs back on and the problems are now worse then ever! No 1, 3 & 4 leak from the overflow AND also now from the main air inlet into the air chamber!
The worst bike I have ever owned, it's an absolute pig! Never buy a bike in boxes   

[fryerk]

Just a thought you mentioned that you are running a Boyer electronic ignotion. I have one on my 500 and that was a pig to start until I replaced the battery. The Boyers are very sensitive to battery voltage maybe that's your issue

[kevski]

I replaced the valves on my 350/4 and found they were not exactly the same as stock so the floats were touching the roof of the carb inside, so i gradually moved the tang to lower the float height until they shut the fuel off, i then moved the tang a touch more just to give it space for wear, the carbs don't overflow like they were initially, i run a delkevic 4 into one and apart from a little hesitation off of idle when riding she runs lovely the plugs are a nice tan colour, in the winter i will get a couple of colortune adaptors and tweek the pilot side slightly.

[Laverda Dave]

Thanks Kevski for the tip, I'd like to try it but I really think I've got a duff set of fuel valves from Keyster. 
I'm going to buy 4 new valves from DS, they are 14 quid each  and I don't know the make of them either, I do not they are not genuine though.  DS sells the Keyster kits for 19 pounds each but I've been down that road before so not buying another kit only to suffer the same problems 
I never had this hassle with the dellorto's on both the Morini and the Jota and the Amal's on the Triton were a piece of cake in comparison 
I should have bought a rough bike but a runner, at least I could have heard it running and would have known the potential problems, the carbs on this one were in pieces in a box.

[Bryanj]

400's are prone to bad starting if down on compression

[kevski]

When i lapped mine in, i used a cocktail stick with a bit of solvol on it for the seat, and the valve fits nicely in a biro tube which i then lightly polished using a piece of stiff card which i poked a cocktail stick through and a little bit of solvol on the tip of valve and twisted the valve in the hole lightly between thumb and finger like seating an engine valve only takes about a minute.