Spark plug burnt?

[Kithmo]

It might be worth trying a bigger gap, the plug in the second picture looks a bit closed up to me (using my feeler gauge eye ).

[JeffW]

Thanks all for your ideas.

I installed some NGK;s I had previously ordered and leaned out the carbs 1/4 turn (I don't have the ColourTune yet) and it ran fine to Hampshire. I checked a plug on arrival and it was a nice tan colour with no oil or soot.

flying farmer - I cleaned the plug from the photo and you were exactly right (no surprise) it was only caked on carbon and not fried. Thanks again for the advice.

Jeff

[Phil S]

plug gap looks far to small

[mole42]

I would put the old plugs back in and see what happens, they rarely go faulty. The pictures you posted are from a seriously rich-running engine.
I am interested in the “pop” sound you mentioned in post #1 - did you do your compression test before or after that?

[JeffW]

I would put the old plugs back in and see what happens, they rarely go faulty. The pictures you posted are from a seriously rich-running engine.
I am interested in the “pop” sound you mentioned in post #1 - did you do your compression test before or after that?

Hi Richard

No, not yet. I will do one this week and report back as I am also interested to see what readings I get.

Once that is done I will also try out the ColourTune I got yesterday and see how rich the carbs are running.

Jeff

[JeffW]

plug gap looks far to small

I read (ROM & on here) they were supposed to be 24-26 thou, so will double check the ones I pulled out. I know some have run with 30 and higher with different coils and ignition systems, but mine is standard (older) Lumenition and Bosch Red coil as I mentioned above.

Jeff

[tonyh]

That looks like oil burning and fouling the spark plugs, even if you do not have to top up the oil on a regular basis you could still have a problem, it could be valve guides or piston oil control rings. Here is an easy check, find a nice long open stretch of road, drive at a steady speed, about 40 mph, after a short distance back off the throttle for a second and then accelerate, if you get smoke from the exhaust on acceleration you have worn valve guides, next test, same stretch of road, again at 40 mph, but this time do not back off just accelerate hard, if you get smoke on hard acceleration it’s piston oil control rings.

[JeffW]

That looks like oil burning and fouling the spark plugs, even if you do not have to top up the oil on a regular basis you could still have a problem, it could be valve guides or piston oil control rings. Here is an easy check, find a nice long open stretch of road, drive at a steady speed, about 40 mph, after a short distance back off the throttle for a second and then accelerate, if you get smoke from the exhaust on acceleration you have worn valve guides, next test, same stretch of road, again at 40 mph, but this time do not back off just accelerate hard, if you get smoke on hard acceleration it’s piston oil control rings.

Thanks Tony - I am at home tomorrow so will give it a try and report back.

Jeff

[JeffW]

...and wrapping up this post as well. The carbs were set far too rich, so leaning them out resulted in nice clean spark plugs. tonyh - no smoke on on either test!

Thanks

Jeff