Eating plugs?

[Smokey_Paul]

Hi all I am using NGK B8's at present and did a 30-40 mile run today. I have started to wein the bike off pre-mix and had only 100:1 ratio approx in the tank now I guess but I still eating spark plugs. During the run today which was around country lanes at approx 3000rpm 50-60mph the bike started to miss and run rough so I stopped and found nothing wrong after a quick look around. The bike would not run clean so I changed the plugs and hey presto back perfect again all the way home.

Any ideas?

I have the mixture airscrew out 1 1/2 turns at present but the plug looks quite black??
The oil pump is set with a bit of slack in the cable and I think I am not smoking too much if a damp bombfire at idle is right lol

Thanks Paul

[gasman]

Hi Paul, had the same with mine, just chewing plugs for the fun of it. Black means too rich, after float level, choke operation correct, needle in correct grove, filter clean, which mine are all ok, I bought some of these spitfire things, saw the demo and appear to work, not tried them yet but they are going onto mine once i get the barrels back. Will let you know how they go. Kev

SPITFIRE MULTISPARK M/CYCLE UNIT  EBAY NO.  270636272043

[Smokey_Paul]

Yes very strange everything on mine is new and set up perfect as far as I can see but the plugs are black!!

New choke mech etc but I do wonder about the main jet size too being so large?

My plugs even sparked out of the bike fine but caused a misfire when fitted, I am going to fit a new zener anyway just for fun just in case the voltage to the ignition was rising.

let me know about the splitfire units

[hendred]

Hi,

I have got my Silk running and MOT'd at last - frame/ engine 124/126.  Firts run yesterday for the MOT.  Had some plug problems so checked the manual.  I am using NGK B8HS at present.  
Manual gives Champion L10 for running in and low speeds, the L10 is superceded by the Champion L86C. The NGK equivalent is B6HS.
For high speed touring the manual gives KLG220 or NGK B8HC.  Modern equivalents for the KLG F220 seems to be the NGK B8HN.  The difference between the NGK B8HS and NGK B8HN seems to be the projection of the earth electrode from the body of the plug.  The NGK B8HN seems to have no projection at all.

Now for some confusion; the Champion L10/L86Y has the same projection as the NGK B8HS.

The Champion L86C/ NGK B6HS runs hotter than the  NGK B8HS and is more tolerant to oil.  I'm going to try the NGK B6HS while riding the bike during the running in period and see if the plug condition improves.

Anybody else tried the softer plug?

Jon

[Smokey_Paul]

That's very interesting I was going to try some different plugs so will look at that and report back, have you tried the B6's?

Cheers
Paul

[hendred]

I decide to put the Silk back on the road immediately instead of waiting for 1st August!  I am using the NGK B6HS plugs as I'm only using it gently while it all settles down.  Most of my plug problems have been due to lack of fuel and over-oiling.  The fuel starvation was due to old varnish breaking free from the bottom of the tank.  All cleaned out and so far ok.  I had the oil pump cable to tight so there was too much oil going to the engine.  The B6HS plugs look good.  My carb is a 38mm Amal mkII with the following jets: Needle 2D, 107 Two Stroke Needle jet, 20 Pilot Jet, 3 Throttle Slide, 490 Main Jet, needle on middle groove.  All the components were on the bike when I got it except for the Main Jet which was a small size drilled out - I used the nearest I had in my spares box to size (480) on the carb page on this site.  I'm using a new K&N RU-0800 air filter as the original filter was missing.

Regards,

Jon
 

[Smokey_Paul]

Well my bike is spinning over fine now, I found the problem was the choke assy and casting on the carb, now changed and cleaned out she is running the best ever

Thanks to the Popham gang