Engine wont start (yes I've searched)

[Jeff T]

So about a month ago I was riding my bike to work when i noticed the spark plug was loose, i tightened it down and kept riding. About a block later i heard a loud pop (sounded like an electrical pop, as if something just fried out), the bike stopped running and wouldn't restart. After doing some research around the forums i did all the usual tests. Removed my kill switch, no luck. Checked the spark, no spark, got a new plug. Still didn't start, got a new magnito coil. Still doesn't start.

It must be something non electrical but i cant understand what because my bike has been running perfect aside from the loose spark plug which had been retightened a few times.

Anyone have a similar problem? What am i missing here?

Thanks in advance!

 

[Al.Fisherman]

Did you run across this?????

Did you remove the magnet and check the woodruff key? There are a total of 4 on these engines, one of which is under the magnet and if sheared, the bike will NEVER start and run.

Without reading through every post I'll start out from both scratch and basic. Testing steps up to you. Don't know what you have covered but my advise is to start from scratch.

Electrical....Compression....Fuel/Air....Exhaust

Timing... Remove the magneto cover. Remove spark plug. Rotate engine so the piston is at TDC. This can be checked by inserting something like a small screwdriver into the spark plug hole. Don't let the piston jam the tool. Look at the magnet/magneto. The magnet cut a ways need to be at 12:00 and 6:00 precisely. If not replace the magnet key. NEXT
Wire... Check wires making sure none are broken off from coil terminals. NEXT
Current..Isolate wires from coil from ANYTHING else on the bike. Using a test light, check to see if the coil is producing. A store bought or a home made test light will be fine.

How to make a very inexpensive test light. Buy a instrument cluster bulb. Bend both contact tabs down. Tabs will look like a loop of a paperclip. Find some very thin wire. A 22ga would be good. Wire from old ear buds, or old computer speakers works great. On one end split the two wires and strip the insulation off (enough to insert in loop and twist), twist wires. Insert one end into "A" and the other end into "B", twist each and tape if you like. On the other end split wire apart about a foot, and strip insulation back about 1" or so. Now you have a $0.50 test light.
Connect one wire from light to the black wire and the other to the blue wire, which one where makes no difference, white is not used and tape off. Place bulb where it will be easily seen while peddling (tape to tube if needed). Peddle to speed release clutch and look at bulb. If the coil is putting out the light will light up. No light replace coil. This test works great at night. NEXT
CDI Connect coil/magneto wires back up to the CDI. Make sure HIGH VOLTAGE plug wire is inserted into the CDI correctly. Get a length of wire, from a old extension/lamp cord is fine. Strip insulation from one end, enough to wrap around the spark plug base (just below the hex) a few times. If any left over twist around itself like a bread tie, and wrap with tape to secure wire. Insert plug into plug cap. Tape plug to tube in a manner you can see fire at the electrode. Remove a cover (clutch, main gear, coil/magneto cover) screw, and strip and wrap remaining end under screw and tighten. Peddle, release clutch and look for a strong spark. Weak spark can cause non start.

 

[Jeff T]

I have taken a look at the magnet loop and the engine shaft, both appear to be fine. All wired connections are intact, I dont know what the woodruff key is/looks like however. Any chance you could post a picture or description of what it looks like and its function?

Thanks!

 

[Al.Fisherman]

I have taken a look at the magnet loop and the engine shaft, both appear to be fine. All wired connections are intact, I dont know what the woodruff key is/looks like however. Any chance you could post a picture or description of what it looks like and its function?

Thanks!

Crankshaft placement is with the piston at TDC.

Here you can see the cutaway for the key. Only seen after removal of the magneto.


Here is the key installed. When installing key and magnet, super glue key in place, this makes for a much easier instillation of the magnet.


This is the proper position of the magnet with key intact and piston at TDC.


This is the incorrect magnet placement, with key installed and piston at TDC


Function....... The key keeps the magnet in place on the shaft, this key can shear off. The engine is totally dependent for voltage produced by the magnet rotating in the coil. If the magnet rotates on the shaft the coil won't put out voltage at the proper time for the plug to fire. The key is made from a softer material then either the magnet core or crankshaft. When the key shears off, like in the case of a backfire, the key will be the first to go, thus saving $$$$$$$$$

 

[give me vtec]

It's the magneto. Same exact thing happened to me and a new magneto fixed the problem. Use a strip of old rubber tubing to put between the magnet and magneto to make it easier to line up with the holes.

For the record my magneto did not show any signs of wear after it blew

 

[Al.Fisherman]

Just for clarification for others...it's the coil that can and does go bad, not the magnet, magneto being both the coil and magnet. In very few cases there are signs that might lead you to believe the coil is in fact bad.

 

[HeadSmess]

definitely no spark?

if the key is the problem, then there would be spark...just not at the right times. the key locates the magnets in relation to TDC. assuming the nuts tight n the shaft is still a good fit... it will turn, just theres nothing to keep it lined up...

but a complete absence of spark would be more electrical.

first...wiring? blue to blue, black to black to earth, and white capped n isolated?

what did you replace? the black box coil or the engine coil and stator?

did you reconnect the black wire? to the engine itself?

replacing everything usually does the trick

 

[Jeff T]

Thanks for those pics Al.Fisherman I'll make sure to double check that the key hasn't sheared off when i get home.

As far as I can tell, there is no spark. It seems that if the key sheared off and the shaft spun freely without turning the magnet then that would be a cause for no spark. As would the coil dying. Right now i have the blue to blue and black to black (i believe the black is grounded inside the engine casing but i could be wrong) and white is capped off.

I'm in talks with BikeBerry to get a new magneto since my engine is still under warranty.

Just for clarification I replaced the CDI (black box that connects to spark plug and engine wire leads). I also replaced the spark plug. So all new wiring up to the engine, and as far as i can tell no spark. Anyone know the resistance readings if i were to try to test the spark plug in series with the rest of my wiring?

 

[HeadSmess]

there is a resistance measurement somewhere... im not searching for it

basically you should get 340 ohms (i think?) across blue/black-earth... anything majorly less is a short and anything huge is open circuit... and intermittent is also a bin model...

whilst a measurement across the white/black-earth is only about 4 ohms...

 

[Stan4d]

http://motoredbikes.com/showthread.php?t=28255
http://motoredbikes.com/showthread.php?t=9619
http://motoredbikes.com/showthread.php?t=23662
http://motoredbikes.com/showthread.php?t=28035
If you still have the problem after following the advice in the links then let me know and I will search your problem again. Search is an awesome tool.