Hi Chris, I should have been more specific, it ran on one for a few seconds when it first started. After that it was fine. I am pretty confident it is not ignition related. Battery is fully charged, updated coils etc from exige. Can you/should you balance the carbs when running on the choke? Or should it be idling without? (This would be difficult atm) Thanks
When you assembled the carbs, did you 'pre-balance' them? Because if you didn't they could be way out. The easiest way to do it, is to use a piece of thin lockwire as a feeler gauge and insert it into the carbs one at a time so that you can adjust the butterflies to have the same slight opening at the bottom of them. OK, it won't be spot on, but it would be a start for adjusting idle speed and then balancing when the engine is hot. As a matter of interest, which cylinder does it run on to start with? It isn't right, but it seems that when it occurs it is the vertical one fires up followed by the horizontal one. It can be caused by excess fuel draining down into the head and wetting the plug.
Thanks Arquebus, I didn’t pre-balance them, rather assumed they were when they were rebuilt. This weekend I will take them off and re-check/start from scratch on settings I think. I will search the forum for some suggestions for each adjustment (and the Haynes manual) You are correct, the vertical cylinder fires first. What you say makes sense and thinking about it when I changed the plugs (before any of this), the horizontal plug was wet and the vertical dry – can this be addressed fully or is it an unavoidable situation due to the cylinder orientation, and one that can just be improved? Would you increase the air mix for horizontal cylinder so there is less fuel being fed? And reduce the air mix for the vertical therefore? Or is it all down to the balance? Thanks very much, this is certainly a learning curve!
It's the balance that you need to be looking at, now you have added more information about plugs it's more than likely caused by inbalance. as I said, you can only set balance approximately off the bike, the fine tuning is done when on the bike with engine running. It's ok to leave idle mixture screws at around 2 - 3 turns out and then experiment with 1/2 turns later.
if both float levels are set correctly/not too high then you shouldn't be experiencing flooding or favouring one cylinder over another unless float/needle valve not working correctly. Just as Brad has said, i've hardly ever had cause to adjust float level heights on a standard bike, and a lot of the Dynojet equipped bikes i've run have often been more trouble than they are worth. float level setting-wise, anything around 13.5/ 14 mm works fine.
The greater the float level height is, the lower the fuel level is......this means that the pilot screws need turning out more. They are all part of the pilot circuit which controls the low rev range running up to about 2000 - 2500rpm. But you say the bike will idle and doesn't die until you touch the throttle, which suggests to me the pilot circuits are roughly OK and you have a major imbalance as Chris says, or possibly that the slides aren't lifting at all, rather than unevenly. Check the diaphragms for condition if you are sure all the other components are in good condition and all parts assembled correctly.
people often get the float setting dimension mixed up with the float level when it comes to high or low - with the float level set too high the carburretor will definitely flood.
evening gents, i really appreciate all the ideas, to put some perspective on the situation - in between your posts i am searching 'how a carb works' - so have i bit off more than i can chew, definitely. your detail and opinion is to be admired. I guess if this was all easy, we wouldn't bother doing it right. I also admit i was so confident, my first rebuild going so well and then i hit the starter...bollocks. As it stands, i have just taken the carbs off again, going to understand how they work (probably should have done this before). this photo is how the bike was looking......
Please keep the posts civil guys. There is absolutely no need to get abusive. Especially over carburettors. It’s not like we’re talking Brexit or lithium batteries ffs I have deleted posts that are just ‘having a go’ at each other.......hopefully that doesn’t detract from the answers the op was looking for.
