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I have had my Falco for over a year now bought second hand and it has never missed a beat till now.

The bike would ride fine when you were on the throttle, but when you rolled off and let the revs drop to low RPM and accelerated again there would be a pop a small delay and then it would go.

My thoughts where plugs and leads, checked it all out and found one of the front plugs (upper one) had worked itself loose.

So i started to unscrew it to have a look at it and could only turn it 2 turns before it binds up and wont unscrew any more. So I screwed it back in and it went in a long way before it seated and went tight.

The bike now seems to run great again, but on 1 or 2 times it still some times has this little pop.

The spark plugs are Iridium tipped NGK so should not need to be replaced for a long time. My thoughts are that the plug may have got heavily sooted up when loose and this is why is does not always fire correctly (hense the pop). This may burn off over time.

Why do you think the plug will not come out, as I would have thought that if the threads where damaged it would not screw in or out. I dont wont to force the plug out as this could break something or drop something on to the piston.


Thanks

Gav

OK, I’ve had a bit of a think about this. If it will unscrew a reasonable amount, I don’t see how it can be the thread in the head. That must mean the thread on the plug extends into the combustion chamber and that part of the thread has a problem.
My guess is that it may be carbon build-up on the plug thread.
I wonder whether you can unscrew the plug slightly and run some decarbonising fluid down the thread and once it has started to clean it up, work the plug back and forth to clean it enough to get it out.

If it really won’t come out after that, I can’t really see a way to investigate further without lifting the head – unless you want to unscrew the plug whatever the damage and risk having to helicoil it.

This is not the first time I’ve heard of Iridiums coming loose – but I can’t see that’s a factor of them being Iridium plugs. Wonder whether it’s something to do with NGK’s Iridium’s thread design and whether the DENSOs are OK – I have those (well, I would being as I work for DENSO – and no, I can’t get plugs for everyone – getting a set for myself was a challenge!)

Hope you get it sorted.

screw the plugs, tell us more about this guy with the cutter for the self made renegade cans!

seriously I think I would go the same way with running a decarbonising agent down the plug and working into the thread - possibly carb cleaner may be the right sort of stuff??

D-Rider wrote: and no, I can’t get plugs for everyone – getting a set for myself was a challenge!)

Not everyone..... just me

If its the right plug there's no way it would protrude into the combustion chamber for the very reason stated.

I would suggest screwing it in and out in between bouts of WD 40 spraying until it eases off - or screw it back in tight and forget about it till next winter!

hey funny that, one of my plugs came lose at the weekend, in fact came right out!
i was trying to make it to a cafe before sorting it.
lucky it was on the rear cylinder, so lift tank a touch and screwed it back in.
have lost the electrode off a new plug in the falco before.
as said stick some releasing agent or diesel down the plug and leave it over night, then very slowly try to work it out.

There are two spark plugs fitted to these engines -so why not pour a few cc's of light oil or `REDEX' into the removable plugs hole, place a rag over the open plug hole and turn the engine over a couple of times.
This should coat the exposed thread with oil which you should then leave for as long as possible.
Hopefully the carbon should have softened enough for you to unscrew the errant plug and replace it without damaging the threads in the head.
The engine will pour white smoke out for a couple om minutes when you fire her up afterwards though!

Ahh the old redex haha

brings back memories ....years ago I put it in a mini cooper (down bores and in the tank) and set off to town.....feckin clouds and clouds of smoke !!!!!!! ...stopped all traffic behind me

You old git OKA,
yeh I remember it well!