Conference noted::motorcycle

    
    you either have a week coil, battery, whole ignition, or oil getting
    in the combustion chamber. I'll guess its a yamaha and the problem is
    the right side cyl.

    Thanks for the response.
    
    If the coil is weak, why should it blow the plugs??
    Also, if oil is getting in, what difference would that make to the plugs
    apart from causing it to burn more oil, and making it more difficult to 
    start?
    
    The B7HS's were in for some time, and the bike seems to be starting and
    going fine now!
    
    The bike dare I say it is a JAWA 350...so I suppose the cynical among
    us would say..."well, what can you expect?".
    
    With only one carb, how does it feed both cylinders evenly?
    
    Anyway,  I do have a spare bike...........I thought I'd probably need it!
    
    Cheers,
    
    Tim
                                            

> Has anyone had a similar situation to myself, where two spark-plugs
> seem to have 'died' in the matter of a few weeks.

	Perhaps you can say what you mean by "died".

	I had a 2-stroke that would foul a plug every 75 miles...  I
	would have to take out the plug and knock a carbon chip out
	of the gap.

    Hello John,
    
    No, the plugs have never been really badly carboned up.
    It seems more like the electrode has blown....although I have to admit
    I haven't put a test-meter across them since I took them out!
    
    Also, the weather has warmed up a bit!
    
    Cheers,
    
    Tim

> It seems more like the electrode has blown....although I have to admit
> I haven't put a test-meter across them since I took them out!

	Sparkplug electrodes don't just "blow" like a fuse...  The
	ignition coils and sparkplug wires are more likely to
	melt first.

	There are typically few things that cause a sparkplug
	to fail:

		1) A chip of carbon across the gap shorts out the
		gap and prevents a spark.

		2) Carbon built up on a 'too cold' sparkplug insulator 
		and caused the electric current to travel through 
		the carbon instead of across the spark gap.

		3) The electrode has eroded enough that the gap
		is too large for the available voltage.

	You can detect case 1 by observation, case 2 by looking at the 
	insulator to see if it is black with carbon and case 3 by
	measuring with a sparkplug gap guage.
		

    Would damp around the insulator also perhaps cause the problem...it was
    after a very cold spell of weather, then it warmed up and became damp
    and mild....so condensation would have built up easily.
    
    I suppose I should have warmed up the plugs on the central heating
    radiators first....that may have helped!
    
    bike still going really well with the older plugs!
    
    Cheers,
    
    Tim

    Well, I've checked the plugs with a meter, and they are definitely
    blown.........wierd!
    
    T

    I have had the same problem with the same plug. If I got caught in the
    rain, rode for a while in the rain. One of the plags would be bad. I
    checked the plugs with a meter, INF ohms. I told the dealer, I brought a
    few bad plugs into the dealer. They claimed I was the only one who 
    complained about these plugs. I since have used champions for a year 
    (18k miles). 
    
    I know that the electrode is not
    one piece, when you break the glass insulator the electrode was three
    (if I rember) pieces.  I donot know how or why they fail, but if I uses
    them I carry an extra set with me.
    
    

> Well, I've checked the plugs with a meter, and they are definitely
> blown.........wierd!

	How do you check plugs with a meter?  Do you have a meter
	with enough voltage to jump the gap?

	One way to check a sparkplug is to connect it to one of
	the sparkplug wires, rest the metal body of the sparkplug
	against a bare metal area of the engine case, then crank
	the engine.  You should see a spark across the spark gap.

    He's probably checking them with an OHM-meter. If that's the case, be
    cognizant of the fact that there are resistor plugs which measure high
    resistance in the center electrode. They're made that way to elminate
    ignition noise in the rf spectrum.
    
    I sold cars for a few months before I started to work with DEC back in
    the mid-'70's. When the dealership received a shipment of Opal's off
    the truck, we'd drive them over to the holding lot. Some of them didn't
    have enough fuel in the tank to complete the trip. If we ran out of gas
    and tried to restart the car without adding more gas, the plugs would
    burn out and the mechanics would have to replace them. I don't know
    why, but have just now opened a rathole, down which we'll proceed at
    breakneck speed, no doubt. The author of the most amazing explanation
    will win a six-pack of Bud, deliverable at my crib here in Boise. But
    ya gotta hurry, I can hear it calling me, even now.
    
    dw 

    ref.9
    
    I put one lead on the top of the plug and another at the base of the
    electrode (not the other side of the gap!)
    
    It worked on a B6HS plug, but not he B8HS's! So I assumed the 8's were
    blown!
    I did check them against the cylinder head on the end of the HT leads
    first and that;'s how I thought they were duff in the first place!
    
    Oh well...it's still working on the BH7's!
    
    Tim
    

    It's now started firing poorly at low revs.
    
    Could this be symptomatic of a coil on the way out, and if so, how can
    a coil be tested?
    
    Otherwise, how do you check an ignition system out??
    
    I'm considering putting on an electronic ignition unit, but nee the
    rest checked out first rather than spend out on that and it's not that
    anyway!!
    
    Any thoughts on the benefits of that as a way forward??
    
    Cheers,
    
    Tim
    

    Speaking with a friend...could it be the rectifier?
    
    the symptoms are RH cylinder firing about twice as much as LH?
    
    Or, might it be the lobes moving the points being
    warn/knackered...maybe an electronic ignition unit would be get over
    the problem and be better than points?
    
    Tim

    The electronic ignition unit has fixed the problem....probably worn LH
    points at point where it rests on the cam.
    
    Cheers Tim