Easy when hot, hard when cold

[Butch (cb)]

Sometimes new plugs just die.

[bsa-bill]

Sometimes new plugs just die

so true - but why considering the simplicity of design and the years that they have been making them

I sometimes wonder if there is some element of conductivity in the deposits left by modern fuel

[a101960]

Sometimes new plugs just die

Yes that is oh so true, and even worse sometimes they are faulty straight out of the box. A while back I bought a new set of plugs for my car. The engine would rev freely with no load on it, but the car was undriveable due to the engine missing under load. I refitted the old plugs and it ran perfectly. Just because a set of plugs are new it does not mean that they good. At least I did not end up changing the coil, leads, distributer cap and other bits in an attempt to cure the problem. The plugs in question were Bosch. On my A10 I have always found Champion to be the most reliable plugs NGK plugs never seem to last very long for some inexplicable reason. Other people have had different experiences. It all seems to be a bit of a lottery to me. I would also suggest experimenting with the pilot mixture if the bike is hard to start when cold. I found that setting up the engine idle as described in the book was a bit suspect. The book settings were fine when the engine was hot, but the engine proved difficult to start when cold. A little tweak to richen the pilot and all was well. I have found this to be especially so if a colour tune is used. Start with the pilot screw at about 1- 1/2 turns and work from there. Well it worked for me anyway.
John

[Gus Keating]

I had a similar problem starting my bike from cold and I was getting frustrated and about to lose confidence in using it, however a friend gave me a tip which has made all the difference.  He noticed that the bike had a concentric carb fitted and he said that when starting it I should keep the throttle closed, ie; no blips. I took his advice and now I tickle it, operate the choke lever a little, keep the throttle closed and kick.  It seems to work, he doesn't know why this should be the case but it was something another BSA twin owner told him.  Gus

[Greybeard]

...when starting it I should keep the throttle closed...

I thought that was the standard advice when starting any engine. 

[Gus Keating]

That may be so Graybeard but many riders blip the right twist grip when starting their machine!    Gus.

[BSA_54A10]

Sometimes new plugs just die

so true - but why considering the simplicity of design and the years that they have been making them

I sometimes wonder if there is some element of conductivity in the deposits left by modern fuel

In a word,
YES
Modern "fuel" which is not petrol is quite conductive at cylinder pressures.
Modern fuel can not be completely burned in our old cold air cooled engines which is another reason to starve the engine off because in the last few strokes the engine is running quite lean and will burn the crud left behind by modern fuel ( which is not petrol ).
Because our dinasaurs represent less than .00000000000000000000000000000000000000000000000000000000000001 % of spark plug sales now days, modern plugs are not designed for their benefit.
They are designed to be installed nto new era lean burn fuel injected engines which run too hot for glazed insulators.
have a close look at an old plug.
the insulator was nice and smooth with a shine on it.
Compare it to a modern plug & you will see the insulator is white and matt looking with no shine to it.
Thee new insulators pick up crud and form a conductive parth very easily

[Rocket Racer]

Following Trevors theme of spark plugs, a few months back I was working on my triple and a mate who happens to be very clever who was helping me get it sorted, commented on my NGK plugs which I had bought and fitted without thinking. I cannot remember the exact discussion but the result was that I refitted the worn old champions and had an immediate improvement in starting the bike. Apparently current NGK plugs are designed for modern engines and if they foul will not clean them selves up...
My father in law has a 650 Benelli S2 which was also a very temperamental starter so I mentioned it to him and he swapped out his NGK's with new mexican champions and he couldnt believe the difference with starting.
After these two incidents I have bought champions for all my beesers 
I had used NGK's for years but apparently they have changed the way the plugs are finished, something to do with the glazing 
Cannot claim its the root of all problems but amazing what difference plugs made in two old school engines.
Since fitting the champions I have not had to remove a plug for cleaning (famous last words that will no doubt bite me!)

 

[BSA_54A10]

The thing you need to remember about Champions Vs NGK's it is apples Vs custard tarts.
Champions have a very very very wide range of not operating properly while NGK's have a very limited range of not functioning properly.
Go to any spark plug interchange site and you will see N3C's range from BP6 through to BP8 in NGK amd I have found that even BP5's work well to replace N3C's with modern fuel.

[muskrat]

The only time I've had plug troubles on the BSA's were on Chumpions. If it's tuned right the NGK's are fine.
Cheers

[Rocket Racer]

In the past I'd not had any issues with NGK's but these issues occured with new plugs bought last year  .
What I believe is that new NGK's are very prone to fouling (in some engines) and that once they do, they need cleaning. Whereas new (mexican made) champions don't have this issue.
My understanding is that NGK have altered the standard of the glazing and it can now cause problems in old engines.

All I'm suggesting is that if your plugs are fouling on start up and you suspect plugs, try another brand