Your spark doesn't sound eratic. You have to figure that since the engine is a four strokes, the spark plug will essentially only produce 1 spark per 4 RPM's. If memory serves me correctly, and this is very basic, your engine has an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. you will only see a spark on the combustion stroke.
-Alex
Some of these engines fire the sparkplug during the exhaust stroke as well, called a "waste spark". I was trying to figure the sparks per revolution out on another thread, and just got a headache... lol
(so intake, and compress are one revolution, combustion and exaust another revolution, the spark fires once every revolution...) or does it?
Apparently different motorcycle engines handle the firing differently, and I could never find a definitive answer. _________________ Spyder 250 (KTR-250W, or GK-29)
Blue (Polini) main Spring
17g Sliders
White clutch springs
UNI filter / 130 Jet
had identical symptoms, turns out i had a bad sparkplug boot. _________________ Kasea AB-150
just another tricky day
12 gram slider rollers
performance cam
performance cdi
If all the parts used work (coil,plug,plug wire, CDI) are good (as they work on the good unit/ other kart) that leaves the pickup in the GY6 (I think) that they are tightly routed in the case if your stator takes a crap it takes out the pickup as well, ( I remember reading that here somewhere), so If it were me I would check the pickup with an OHM meter to see if it is shorting to ground during crank, you could do a physical look see, if you are unsure of the meter results,
Just my thoughts
Tim
BTW I would only use the head when checking spark, the ground wires to the chassis are lighter and carry less voltage.
It could give you a false reading _________________ Turbo Turtle(for the little man)
XYKD260-1,
Stock; air in the tires and wind in my face!. Everything else has been Simacated!
Active member of MBRA and NEBA.
Some of these engines fire the sparkplug during the exhaust stroke as well, called a "waste spark". I was trying to figure the sparks per revolution out on another thread, and just got a headache... lol
(so intake, and compress are one revolution, combustion and exaust another revolution, the spark fires once every revolution...) or does it?
Apparently different motorcycle engines handle the firing differently, and I could never find a definitive answer.
I will do some more research on this, but either one of us could be correct. I belive the "waste spark" is usually intended as an emissions feature, but could not be accounted for by the manufacturers of off road vehicles. As I said I will research into it and get back to you. _________________ -Alex
www.kidnmekarts.com
-Service Tech Extraordinaire
" but either one of us could be correct" It's not about whos wrong or right, just information shared amongst fellow buggiers.
And I hope to meet you tomorrow.
Tim _________________ Turbo Turtle(for the little man)
XYKD260-1,
Stock; air in the tires and wind in my face!. Everything else has been Simacated!
Active member of MBRA and NEBA.
Not to put to fine a point on it but the spark would be every other revolution, unless you have a wasted spark engine, in which case it would be every revolution. A "stroke" requires only 1/2 of a crankshaft revolution. The 1st half pulls the piston down (intake)the second 1/2 pushes it up (compression) etc. That is why the camshaft is geared 2-1 with the crank. The "wasted" spark is just that. It's easier and cheaper just to fire the spark plug on every revolution. No need for a distributor and less programing in the CDI. It works well on single cylinder and even cylinder (2,4,6,8 etc) engines. In the even cylinder engines they fire 2 at a time. Every time a cylinder is on the ignition stroke there is another on the exhaust.
As for the problem at hand, if you haven't already checked all of your grounds to make sure they are clean and tight you might try that before tearing open the engine. Also try swapping the ignition switch or bypassing it. They do go bad with water and dirt getting in there. Even if it cranks fine the ignition circuit runs through there. I've had to change mine twice. _________________ 05 Jehm Adventure Buggy 250cc, Torque Spring, 22.5gr Rollers, Modified Roll Cage, K&N, 21x7x10 & 22x11x10 Trac Star Radials, Vapor, Body Panels, 40T Spkt
&
2003 Jehm Blazer 125cc, Vapor
10 gram rollers, 20x10x8 Razr's,
34 tooth sprocket, 9pk cooler
As for the problem at hand, if you haven't already checked all of your grounds to make sure they are clean and tight you might try that before tearing open the engine. Also try swapping the ignition switch or bypassing it. They do go bad with water and dirt getting in there. Even if it cranks fine the ignition circuit runs through there. I've had to change mine twice.
Agreed; Opening the case is a last resort.
Tim _________________ Turbo Turtle(for the little man)
XYKD260-1,
Stock; air in the tires and wind in my face!. Everything else has been Simacated!
Active member of MBRA and NEBA.
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