I have got SWM 280TL which runs OK for about an hour then fouls or buns out the plug. If I change the plug it then runs OK again. I am using a BP5ES plug. Any advice or possible cure would be great.

JGM

Have to be a bit more descriptive. Oil fouled, carbon (dry) fouled, or white deposit fouled?

Oil fouled

Post a photo of fouled plug.

Oil mixture, jetting, bad crank seal on primary drive side. Worn needle/needle jet, float level, ignition timing not sufficiently advanced, worn rings/bore, wrong spark plug heat range.

Obviously the easiest is to go up one heat range on the plug. If that works you save yourself a lot of work. On an engine that old there's a good chance all of the above play some role.

you could try a little less oil 

Not wanting to drive Martin mad again with a question... I have it seems, the plug it left the factory with and I have decided to change it whether it needs it on not.. Can someone point me in the right direction on the NGK I might need. Oh I nearly forgot 1978 320...

Merci Beaucoup

As far as I know, it's always been BP5ES, or equivalent, Mon ami.

Cheers Ross..

You might try BP4ES my SWM had also burnt some BP5ES which happened in the silliest moments.

 

Now I use the hotter plug and everything works perfect even the plug colour changed from black and very dark brown to dark brown at the edges and brighter brown in the middle.

 

I still use BP5ES when the bike has to do longer road travels, but training and competition I do with the hotter plug. Had not to replace the plug so far after over one year of riding, looks still very good.

Patrick,

it always happend in the silliest moments.

You can always cross reference your plug out to a iridium NGK or denso . They need alot less energy to fire correctly from your old ignition . Been running the same one in my Fantic for years now , still starts like new ... and looks the part .

Glenn

Hi, I've got a similar problem with my 125. It's running a bit rich, the plug is really black, even though I've gone down with the main jet from 78 to 70. The engine starts fine, pulls well until it dies. It's got new crank seals, a new carb/crankcase inlet rubber, the carb has been stripped, cleaned and put together with all new internals. Once it dies, even though there is a good spark, fuel in the tank/carb, the breather pipe is open, the airfilter is clean but the thing won't start.

 

If I put a brand new NGK plug in, be it a standard or iridium equivalent, it starts first kick.

 

Any ideas ?

 

Thanks,

 

Phil

Condensor

Agree