Hi
just a query re the spark plug. I have this m20 thing with the b33 engine. the engine has a high comp piston and posh cams etc.
the first time i rode it it heat ciesed because of being too lean.
i run it a bit rich now because I'm concearned it might be too lean with lower needle and smaller main. (took ages to track down the new piston)
it was fine to start with, just a bit of a sooty plug, but didnt give any problems.
now everytime I ride it the plug has to be removed and cleaned or it won't start.
I am wondering if this is because the continuous fouling and cleaning has ruined the insulation of the plug insulation bit, making it spark weakly and thus more sensitive to fouling.
and I am wondering weather to go up to a 'hotter' plug to see if i can keep it running without adjusting the carburation.
hmmmmm..

email (option): hutman80@hotmail.com

Hi Maxell,

A nice piece..
Can also be that this specific sparkplug is a faulty or that the magneto is too weak for the high comp,
So need a good cleaning.

If you test the plug when not able to start the bike and before cleaning,
You probably see it sparks when not in the barrel.
Noam.

email (option): noam10@gmail.com

Hi Maxwell, What plug grade are you currently running?...Ian

email (option): ian@wright52.plus.com

Hi Maxwell..Either an L82C Champion or an NGK B6HS should run OK in your engine. Ideally the mixture should be niether weak nor rich, and there is no real benefit in running it over rich, in fact if it is really rich you can wash the oil from the bore and piston....It sounds as if you may need to make some adjustments to the carb settings. If your piston clearance and ignition timing are correctly set and you are following the usual running in procedures you won't have any piston problems with the mixture correctly set. It is worth comparing the spark with the engine cold and then hot (with the correct plug grade fitted and gapped to .018"). If you have a blue spark when cold and a weaker, yellowish spark when hot your magneto may be in trouble...Ian

email (option): ian@wright52.plus.com

i always understood that cleaning a plug with brass wire brush or sand blasting them this put micro scratches into the ceramic core cutting the insulation qualities down new plugs or nothing but money comes into this equasion so it was done

email (option): roger.beck@node6.com

hi yea cant remember off hand what plug is I'll have a look tomorrow, I think its ngk b6hs or whatever.
i'm hoping it's a not a mag problem as I paid for it to be recondiditioned.
i set the timing as standard for b33. it runs good at speed, feels a bit lumpy lower down.
should the timing be changed for high comp piston?
Yea theres no spark when fouled, a bit of a clean with sandpaper and then theres a weak blue spark.
so yea, it has
new mag
new 'run in' high comp piston
run a tad rich
was fine but now isn't
If i remember correctly, i moved the needle up one notch and it went from too lean to too rich. ( although I had previously forgotten to blank off the unused choke cable hole, which didnt help )

email (option): hutman80@hotmail.com

Maxwell, just an idea I want to run past you. If the engine was put together with tight piston skirt clearance, it could start to nip up after getting a bit too hot during the first 50 miles & the Carb settings might have been fine, now you have richened it too much.
Hope you don't mind me thinking out loud but that's my first thought when I read it.
I would run the bike with original settings & check the plug colour,
Hope its clear what I mean, I can't help thinking it wasn't weak mixture that caused the seize.

hi yea no worries, i got the engine in good shape already run in with a genuine bsa piston.
my first ever ride it ciesed (seezed?)
the plug was torched as well
so the original ciesure was the already run in well used piston.
i got a new one an a re bore.

I'm thinking now it may be that choke cable hole that caused the problem (I forgot about it)
I think ill probably have to adjust the carb after all

email (option): hutman80@hotmail.com

yea plug is champion l82c

email (option): hutman80@hotmail.com