Interesting problem ?

[old red eyes]

In the last couple of months my @'s fuel consumption has dropped to around 35 mpg and runs like a pig when cold but seems ok once warm. I thought it might be the choke sticking so just left it as it was due a service. Today I stripped it down for valve check etc. when I went to remove the rear plug on the rear cylinder I noticed it was very loose, when I took it out the tang that covers the electrode was awol.
What to do next is the problem, I fished about with a magnet thingy but never picked anything up. Should I just leave it and see how she goes or do I take the head off in the hope that I can just pick out the missing piece?

[YEN_POWELL]

In the last couple of months my @'s fuel consumption has dropped to around 35 mpg and runs like a pig when cold but seems ok once warm. I thought it might be the choke sticking so just left it as it was due a service. Today I stripped it down for valve check etc. when I went to remove the rear plug on the rear cylinder I noticed it was very loose, when I took it out the tang that covers the electrode was awol.
What to do next is the problem, I fished about with a magnet thingy but never picked anything up. Should I just leave it and see how she goes or do I take the head off in the hope that I can just pick out the missing piece?

Try a piece of string covered in thick grease down the plug hole. That's if it hasn't already been blown out of the exhaust valve with no damage. Also it may be worth tyring to borrow a fibre optic camera to see if it's there or not. Better than pulling the lid off eh.

[GSPD750]

What to do next is the problem, I fished about with a magnet thingy but never picked anything up. Should I just leave it and see how she goes or do I take the head off in the hope that I can just pick out the missing piece?

If it was my bike...I would install a new plug and ride it. Chances are the ground electrode or the tip is long gone now. You know if you have ever adjusted the gap that the electrode is soft and hopefully the valves and seats faired better which are much harder.

[old red eyes]

I like what i am reading, it had occured to me that it would possibly find its own way out and as GSPD750 says they are pretty soft metal. So new plugs and ride it is.
Thanks guys.

[Dilbert]

What does the remaining bit look like, has it snapped off or just melted away, if it's melted away then there shouldn't be any bits inside.
If you gently turn the engine over to get that cylinder to top dead centre (ish) try poking one of those mini keyboard vacuum cleaner thingys in through the plug hole, but like the others I don't think you'll find anything.
If it was going to do any damage it would jam between the piston and barrel, dig in and maybe snap a piston ring, more likely it would get sucked out by the exhaust gas, if you ran it for more than a couple of miles it will most likely have done one or the other by now.

[Sye]

I doubt you will fish it out or that it has been blown out of the exhaust. It will be firmly welded to the piston crown. If it's done no harm by now, I doubt that it will. As time passes the heat will make it 'as one' with the piston. Fit your plug and forget it.

[Lord Stig]

Yep, don't worry about it - I've had this happen once or twice and no harm came of it. I had bad damage on a Vauxhall Nova #1 piston crown once, which was caused by the plug itself totally collapsing, but the car ran fine, and when I took the head off there was miraculously no evidence of debris left.

Stig

[old red eyes]

Job done bike running like a dream. Just one other thing when putting everything back together I notice that the pipe that links the 2 carbs together just below the airbox does not have anywhere to plug into, have I missed something or should it just dangle.
Please dont suggest that I take dgi pics before stripping things down. I know I should, it must be an age thing but if I start a job one day and finish it the next I always forget where half the things go.

[xrv_jim]

...if I start a job one day and finish it the next I always forget where half the things go.

Those things immediately become 'spares' - it's workshop lore.

Have you also noticed that you invariably find one less nut or bolt than the number actually required?

[YEN_POWELL]

Job done bike running like a dream. Just one other thing when putting everything back together I notice that the pipe that links the 2 carbs together just below the airbox does not have anywhere to plug into, have I missed something or should it just dangle.
Please dont suggest that I take dgi pics before stripping things down. I know I should, it must be an age thing but if I start a job one day and finish it the next I always forget where half the things go.

There is a dangler in that region. That same question has come up a few times. Look inside the end of the pipe. Does it look like it's been on the end of something or is it unmarked?