If I have current through the spark plug wire, but the plug still won't spark, what could the problem be?

Question

It's a '71 yamaha dt 250. It's a new spark plug and I replaced the stator and ignition coil with used parts. I even tried a couple different spark plug caps and got the same results.

river rat, ground it? run a wire from the plug wire to the frame?

Answer 1

Everything that ever goes wrong with anything is either
a)Bad Ground
b)Carb Adjustment

If that dont fix it,,get a Bigger Bike.

:)
,,,,,,,,,,,,,,,,,,,,,,

Seriously now,,,Magnetos wont produce enough juice to spark unless
a)the Condensor is Good
b)The Points are CLEAN
c)The Ignition Timing is set properly

Yes,,that's a Fact of the nature of magnetos,,
They Will not "Fire" if they get too far out of time.

That's why they quit firing when they shear a flywheel key,,,and flywheel slips out of phase.
NOT merely because ignition timing goes wacky w/ flywheel outa position.

Case in point:
Briggs & Stratton Lawnmower Magnetos function "Identical" to motorcycle magnetos.
But Their flywheels Do NOT include the Points Cam.
B&S Points are operated by a Cam ground into Crankshaft.
You can REMOVE the Flywheel and their Ignition Timing & Points Opening/Closing remains Unaffected.

But Shear a Flywheel Key and allow Magnet/Coil Phasing to shift when Flywheel slips outa position,,,,
NO SPARK is the result and engine dies.


Battery powered ignition will fire "anywhere".
Mags Wont.

They'll Make enough juice to Feel,,,but not enough to fire a spark plug,,or not enough for proper ignition.

Make sure Timing is set close,,,and points are clean

You can use an ohmeter to check the Condensor,
and also a flashlight or transistor battery & a Voltmeter.
Wont tell you if it's Right/Correct/GOOD,,,
But it will tell you if it's BAD


You may have other probs,,
But I'd start by verifying those things
and at least eliminating them as variables

Good Luck with it

Answer 2

no factors must be a more advantageous recent quantim motor they suck now that they have elimenated maximum the little tricks one replaced into once able to finish id advise that first of all you remove the tank and drain it then pull off the carberator and sparkling the finest you could replace the diaphram gasket less than the carberator positioned tank back on refuel and be conscious what occurs have you ever bumped off the plug and level-headed it out on the body or head to ascertain it has solid fireplace if all seems solid after this and it doesent commence is it a backyard mower ?? if someone hit something even as cutting grass like a stump or pipe contained in the floor and so on it may then be the shear key that's positioned less than the hat on the right of the crankshaft if the most is sheared off it throws the timing out so it gained't commence to get to the shear key remove the hat the position the pull twine is take away the show now you need to remove the area that the show replaced into connected to sorry i neglect the call of it notwithstanding it has 2 to 4 little ears the position the show replaced into connected to it they make a device for this yet i doubt once you've one i exploit a brass bar to remove it via taking the bar and a hammer position the bar on between the ears now tap it to the left to loosen then remove being carfull now to not lose any of the ball berrings interior remove the washing gadget on correct the flywheel now theres a touch slot decrease contained in the fringe of the crankshaft it really is the position the sheer secret's positioned you need to be able to seem at this slot and be conscious if the most has been sheared because it is going to now no longer line up if that's the case remove the flywheel via putting the brass bar on correct the crank shaft even as prying up on the flywheel supply it a fantastic wack with the hammer it is going to come correct off now go get a clean sheer key and reassemble the motor making use of a touch white greese on the right of the crankshaft and so on nows a fantastic time to sparkling and oil issues take a small piece of sand paper to the magnito there are 2 spots the position it allmost touches the flywheel sand them gently this can be sure the priority i know it sounds complicated yet its fairly noticeably ordinary in case your mechanicly prone

Answer 3

Good answers so far. My bet would be the plug, first. If it's carboned-up, that can bleed off high voltage to ground pretty quick. If it's a resistor type plug, the internal device in the plug tower could have opened. Cheapest fix first: clean the plug. Next, replace it. Third, the plug wire itself. Only after these checks would I go deeper into the secondary (high voltage) system.

Answer 4

Ground the plug wire and crank...then check it for a spark... should it give a momentary spark and then quit again you will need to replace the ignitor or if it has old style points and condensor pull the flywheel and replace...

Answer 5

Did you try replacing the cables? Just because you have current it doesn't mean you have enough for the spark plug to spark.

Answer 6

Ignition switch.
Engine kill switch.
Points and/or condensor.
Sheared woodrift key (it's on the crankshaft to keep the flywheel from turning on the shaft).

Answer 7

here's a link to them on ebay.

Answer 8

you have a bad sparkplug.