Sodding MZ

What is it with you and spark plugs?

 

You. And you, SteveH. **** off both of you. Now. Before those amateur
humorists on ukrm hear of this.

 

Too late....

 

You're dead.

 

.... much like your spark plugs, really.

 

I'm reading this thread with a vague sense of incredulity. Surely the whole
strokers and spark plugs thing is in the "as any fule kno" category? How
did it take three days of clowning about with it to try the first thing on
the list?

 

I dont think it was that simple.
Start out with a bike that worked when he collected it.
Fumble starting and flood it.
Soot up 2 plugs trying to get it going.
Leave plug out overnight to dry the flooded crankcase.
Fit new plug and it starts.

Same bloody thing happened to me with the Jawa.
Par for the course.

 

Well, I tried a spare plug on Saturday afternoon. I'd have bought a new
plug then, but the shops were shut. As they were on Sunday. Monday was
the earliest I could get a new plug.

 

All I can say is serves you right for pratting about with SO-Stinkwheels


<D&RFC>

 

This MZ, did it make it any further than drei und funfzig feet?

 

Thus spake steve auvache () unto the assembled multitudes:

A TOG bike and *two* iffy plugs, no less, which is surely even harder to
believe.

<ducks>

 

The plug type was something like an Autolite #53, was it?

 

I've never had a 2T plug die. I've had slightly better starting &
running from a new plug, but that's all. This despite owning a 250LC,
a CZ250, two YZ250s and various 2T gadgets.

I *did* have plug die in the Guzzi, but only because the spark plug
overheated to the point that the cylinder was pre-igniting: the side
electrode grew a blob of alloy and curled inward to touch the centre
lecetrode..

 

I can easily believe it - I once put a new set of plugs into a motor and
spent days finding out that poor starting and an intermittent misfire were
caused by a dud one.

I've a theory that on older multi-cylinder engines, only one pot actually
fires on the starter - in this case, one dud plug made it almost impossible
to start.

 

Do you have any evidence to back up pthis theory? Personally I don't
see how it would be possible - whether one set of points per plug,
doubled-up points (using "lost spark") or a car-like distributor, all
the plugs are going to spark at the right time, all the valves will be
opening and closing and fuel mixture will be going into all pots.

Actually, ISTR that some ducatis or some other V-twin[1] only have a
choke on one carb, so I guess cold starting in that case may indeed
act as you suggest.

[1] Although whether a twin is a 'multi-cylinder' engine I'm not sure.

 

Ace wrote:

Wotcha.

I seem to recall that my old Gold Wing had an accelerator pump on just one
of the four carbs - which explained why "wanking the throttle" after it had
been standing helped it start up again. Most strange - you could start that
bike with ease, but if left for more than a couple of weeks it would be the
Devil's own game to get it running.

 

A lot of modern bikes have a vacuum operated fuel tap. If the fuel left
in the carbs has evaporated there is no fuel to get it started and you
have to crank like mad to work up a vacuum to get some fuel.
The solution is simple - switch the fuel tap to the prime position.
Just dont forget to switch it back once it starts.

 

well, this one was a 4-cylinder ford 1500, and with the dud plug in it
wouldn't start on the starter, but would by rolling down a significant hill.

I've also met the same issue on another engine, one plug lead accidentally
left off made it fail to start, where you'd expect it to start and run on 3.
Same applied to that one, rolled it down a hill and it did then start on 3,
but start on the starter? no chance.

I guess that with an old engine, one pot is always slightly better than the
others in some way, and that one is the one that actually kicks off on the
starter. It's just sod's law if the one that's most likely to fire has a
dud plug or the lead off.

On the 1500 ford, replacing that one dud plug with one of the old set made
it start with no trouble.

 

*Waves*

They start on one pot and the other chimes in when it's finished its
Chianti.

 

What nonsense!

Explain to me how the engine "knows" that it's being turned over by
the starter, and should therefore only fire one plug (as compared to
when it's running, and firing all plugs)