A few thoughts..
Hi Ady,
Here are a few thoughts, I'm no expert I should add but have had similar troubles and so have tried a few bits from advice on the Forum:
1 - Plugs
The NGK are a "projected" electrode and so better that the Champion for producing a spark which will burn off fuel. There are a number of riders who are not keen on NGK plugs and I have changed to Denso which has had a positive effect - I use Denso W20EP-ZU platinum electrode and am waiting for some WP16 which will help more with a pot running rich. Bear in mind I run electronic ignition and so you should check that the plugs will work OK for you on the magneto. The plug gap is quite important to get right too - magneto may need a different gap than electronic I think.
I got my plugs from sparkplugs.co.uk and they were very helpful with technical advice so I'd recommend them to you.
I've had good results with Denso and would recommend you tried them.
2 - Valve Clearances
Worth checking that these are set right before you do too much else, if they are not, then they can affect rich running.
3 - Carb setting
You mention that you have got new carbs - I guess from Burlen Fuel systems or Surrey Cycles or the like. It's worth checking the specification of the parts fitted - I think it should be 106 needle jet, 170 main jet and needle in the middle position. I bought new internals from Burlen Fuel systems for my original 276's and it largely resolved the problems and I am now into fine tuning. I have heard of people having problems with new parts - a bent needle was one incident I heard of so it is not safe to say that because they are new carbs then all will be well.
4 - Carb Tuning
Forgive a basic question - but have you got access to the AMAL tuning guide (also reproduced in "Know Thy Beast") as the instructions for setting the airscrew may well have an effect on you tickling the carb and flooding.
5 - Air Filters
I run with air filters - which richens the mixture - if you have likewise you may wish to try without.
6 - Fitting
Worth checking the fitting of the carbs and that all is well and correct.
7 - Magneto
I'm defintely no expert on the magneto and so will leave that for other Forum members to advise you on - but worth getting it checked for health - I have heard so many people have difficulties - personally I am blessed that my bike had been converted to Pazon ignition before I got it - and all hidden away under the magneto cowl so you can't see the change - just benefit from it.
8 - Resistors
Worth checking if the caps are resistorised - most now available have 5Kohm - but a resistorised cap and a resistorised plug may well lead a magneto to stop playing ball I would guess. They do exactly what they say on the tin - create a resistance.
9 - Float setting
As you specifically mention this it may be worth checking that the float needle seats properly and shuts off fuel - I polished mine in between the needle and the seat to make sure it was seating properly.
10 - Fixings
I had a jet block union nut (the bottom one on the carb) work its way a little loose - this can cause the bike to run rich. Worth checking that all the nuts, bolts and fixings are tight.
Finally four suggestions, firstly what about going along to your local VOC section meet and seeing if you can enlist the help of some of the membership - usually from my experience you'll find them a helpful bunch of mostly friendly people - I have a couple I have come to rely on a lot who pop over to help me in the garage and watch over to make sure I don't do anything stupid.
Secondly continue to use the Forum as you have started - lots of great advice and replies.
Thirdly - listen to everyone and read all the books - but then make your own mind up what to do, there are lots of different opinions out there.
Finally, was the bike running properly before - if so what have you changed - it is likely that what you have changed has created or made worse the problem - remember to only change one thing at a time and by a process of deduction identify where the issue is. Changing plugs, points, carbs and more all at the same time is asking for trouble.
Best of luck and keep us all posted.
Regards
Stuart
Thanks for getting back to me, my bike has a standard mag and uses NGK BP6EV plugs im not sure if the plug caps have resistors though. It originally had Champion plugs but appears to like NGK's better. When kicking the bike over I get a nice blue spark at the points and at the plugs....Ady