Sooty, black but dry.
Hi Simon,
Many thanks for your interest and reply.
The plugs are coming out very black, sooty but dry. My own reading and research suggests rich running as you say, although I have had a coupld of pieces of advice about oiling up - one being a failed scraper ring and the other the age old discussion point of rocker feed bolts - mine don't have metering wires but the engine has been rebuilt with new valves, guides, in fact everything from the pistons upwards as well as all new primary and timing sides. There is a possibility of a problem but it will be a component misassembly or failure issue rather than wear I think.
So I do hope that you are right - here is what I plan to do....
I am leaning towards carburation as the problem - and that is where I am going to focus my attention next.
Although my father has always brought me up to change one element at a time to resolve problems I think I have enough information now to do the first four at one go and then try the bike:
1 - Spark Plug choice
I have done a bit of research on spark plug choice and intend to try some NGK platinum plugs as well as some Denso ones - both with an projected electrode which will run slightly hotter than the unprojected Champion N5C. I don't think I will try Iridium plugs just yet.
My plug advice is saying:
"Denso ZU platinum options would be W20EP-ZU (projected) or W20ES-ZU (non projected), these are non resistorised plugs. You may be able to use an Iridium plug with your electronic ignition, perhaps Denso IW20 (projected).
If you are persistently fouling plugs the problem is more likely to be carburation but you may be able to work around the problem with a warmer plug, IW16 or W16EP-ZU. N5C is a non projected plug and therefore will have the effect of running a little cooler than BP6ES for instance"
I had thought that the NGK BP6ES was a direct swap for the Champion N5C but this would seem to suggest that the NGK will run hotter and so would be a better bet. The Denso W20EP-ZU looks like the Denso weapon of choice to try.
2 - Clean the carb thoroughly
I am going to combine this with stripping the carb completely (jet block out)and giving it a thorough clean and inspection and reassembly.
3 - Drop the needle one notch (then 2)
I'm going to drop the needle by a notch to start with.
4 - Redex
I'm going to add a dose of Redex for carbs to the petrol.
Then I'm going to go for a good long run (weather permitting) and keep my fingers crossed.
After that, if it does not solve the problem, I'll put the needle back to where I started and look at firstly jet size and then cutaway size to follow as I follow the AMAL tuning notes guide and seek to sort out the richness I think I have.
If all that fails - then I think I am heading towards exploring the oiling up suggestion.
Thanks again for your interest Simon, it's much appreciated - I'm finding the problem very frustrating and as you can imagine it is spoiling my enjoyment of the bike.
I'll keep the Forum posted.
Regards
Stuart
Hi Stuart,
You state the plug is fowling up when running but are not sure if it's oiling up or running rich. In my experience, if the plug is very black but a sooty dry appearance then it is running too rich and is due to carbaration. If the plug is very black but wet appearance then it is oiling up due to worn valve guides or pistion / rings. Hope this helps.
Simon.