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Not very Flexible at all, six foot tall and 360 pounds, and stuck in an electric wheelchair most of the time. I crushed my ankle almost 20 months ago and have had four surgeries so far, with at least two more in the future. I can walk a little bit, or stand for a few minutes at a time, so wrenching on this SP is problematical for me. I blasted WD-40 into the plug holes and tried cranking it for 3 or 4 seconds at a time, don't want to over heat the starter. I will try again tomorrow to get it to start, but if that doesn't work, I will have to pull the battery out to check timing. If that is correct, I will have to pull the engine to remove the intake manifold to see if the rotor is damaged or broken, or something else along those lines.
 
motor pull!

Hate hear of your disability. But I'm sure you make the most of it. You shouldn't have to remove the motor to check the timing, although I agree it would be easier.
Do your plugs have a nice blueish colored spark?
 
Timing?

Unless you fooled with your rotary valve plate or removed your trigger coil on your magneto, you should be in time.
I've read your post, I was wondering what the chances are that you got your spark plug wires crossed.
I can tell you how to find out. Take both your plugs out and removed your shaft guard on the back. With power going to the engine, put a small screwdriver into the MAG piston spark plug hole. Take your plug wire for that cylinder and use another screwdriver to put into the boot then hold it close to the ground.
Roll the engine over and watch the screwdriver in the piston. Right before that screwdriver reaches the top of its travel, you should get your spark. It it doesn't spark before top dead center, then try the other plug wire. It if sparks right before top dead center, then there's your correct plug wire.
This little test may take a friend to help you do it. Don't use the starter motor to turn it over, use your hand.
 
Crossed Plug Wires

I don't think crossing the plug wires will make a difference. I'm pretty sure both plugs fire at the same time( 1 coil...2 wires). This is not true with the fuel injected 2 strokes ( RFI and DI ). On these engines each clylinder has it's own coil and they fire independent of each other. Good luck!!

DAWG
 
Research in progress!....

I'm gonna have to look that one up DAWG.......I can see where your coming from, cause they do have one coil, but I believe they do send out two sparks. Reason being is because only one piston at a time reaches TDC. If both plugs fired at the same time, then that means one cylinder would ignite just BTDC and the other would ignite on the exhaust stroke........
hmmmmmmmmmmmm, I'm gonna have to go into the manuals and read up on that one!......
 
I thought that they both fired at same time one on compresion stroke and the other is on exhaust stroke. I came up with this conclusion when i installed a new digital tach i had to set tach where 2 sparks = 1 rpm as with only one spark = 1 rpm i was turning 6000 rpms at idle and I knew that was not a true reading. but I am not positive. cant wait for the answer as i was kind of wondering about that my self. but i feel 99% sure. but i have been wrong before
 
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I doubt I crossed the plug wires, they are different lengths and the short one can't reach the #2 plug.

I wasn't thinking of pulling engine while checking timing, I just have to remove the battery for that. If I need to delve into the side of the engine, I will have to pull it.

As far as the coil sending out spark to both plugs at the same time, it makes sense, no fuel would be burned if the plug fired in the non-compressed cylinder. It would need a far more complex timing system if it were to differentiate between the cyls.

The spark I am getting is a good blue color, perfect for this application.

I wish I were better at diagnostics, it is what kept me out of professional vehicle repair as a career. I spent two years at an Automotive Technology Majors Program at my local college, and while I passed most of the classes with excellent scores, my diagnostics in more complex situations was severly lacking.
 
you seem to be doing good just keep your mind open to other ideas you will get it. i still thank you may have not got enough fuel to cylinders for some un known reason. but i can be wrong. did you try to flood it with the primer and make sure plugs were wet. i have used wd40 on engines but for some reason not all would start on it but they would all start on gas i guess gas is more explosive but i am not positive
 
The plugs are dry as a bone. I even tried spraying WD-40 directly into the plug holes, with no better luck. I am wondering if maybe the fuel pump on the Carb might be clogged. I will check that out later today.
 
I'm gonna have to look that one up DAWG.......I can see where your coming from, cause they do have one coil, but I believe they do send out two sparks. Reason being is because only one piston at a time reaches TDC. If both plugs fired at the same time, then that means one cylinder would ignite just BTDC and the other would ignite on the exhaust stroke........
hmmmmmmmmmmmm, I'm gonna have to go into the manuals and read up on that one!......

I beleve that i have seen other engines about 20 years ago that fired on compresion and exhaust. i thank it may have been for emissions reasons or it could have been a cheaper way that worked. I am not sure what the reason was.
 
Spark

The reason I'm saying they fire at the same time is because it doesn't matter which plug wire you connect the inductive pick up of a timing lite to in order to check ignition timing. Either plug wire will do.
DAWG
 
2 strokes...

Robin, 20 years ago, what you learned was the cycles of the 2 stroke engine. Unlike a car, which is 4 stroke, intake, compression, power and exhaust, the 2 stroke combines two of those to create a spark on every revolution of the piston.
Every half revolution of the flywheel, a critical point occurs when the position of the magnets changes the polarity of the current flowing through the generating coil. The CDI module detects the change of polarity and signals at the right time, to create spark to the coil. The MPEM sends the signal to tell the coil, which plug gets the spark.
Although I was certain that both cylinders didn’t fire at the same time, I felt the need to research the 2 cycle engine to put to rest any questions you may have about the operation of this engine. The easy way to know that the engine didn’t fire both cylinders at the same time, is due to the relation of the piston on the crankshaft. If they both rose and fell at the same time, then I could see spark at the same time. Of course, that isn’t feasible because the opposing forces would tear the engine apart.
The 4 stroke engine has 4 cycles. The intake, compression power and exhaust. The spark plug fires every other revolution of the piston. The 2 stroke has 2 cycles. The plug fires every revolution. The below is a brief summary of the cycles of the 2 stroke motor and how it works

Fuel Intake
As the piston finally bottoms out, the intake port is uncovered. The piston's movement has pressurized the mixture in the crankcase, so it rushes into the cylinder, displacing the remaining exhaust gases and filling the cylinder with a fresh charge of fuel, as shown here:

The Compression Stroke
Now the momentum in the crankshaft starts driving the piston back toward the spark plug for the compression stroke. As the air/fuel mixture in the piston is compressed, a vacuum is created in the crankcase. This vacuum opens the reed valve and sucks air/fuel/oil in from the carburetor.
Once the piston makes it to the end of the compression stroke, the spark plug fires again to repeat the cycle. It's called a two-stoke engine because there is a compression stroke and then a combustion stroke. In a four-stroke engine, there are separate intake, compression, combustion and exhaust strokes.
You can see that the piston is really doing three different things in a two-stroke engine:
• On one side of the piston is the combustion chamber, where the piston is compressing the air/fuel mixture and capturing the energy released by the ignition of the fuel.
• On the other side of the piston is the crankcase, where the piston is creating a vacuum to suck in air/fuel from the carburetor through the reed valve and then pressurizing the crankcase so that air/fuel is forced into the combustion chamber.
• Meanwhile, the sides of the piston are acting like valves, covering and uncovering the intake and exhaust ports drilled into the side of the cylinder wall.
It's really pretty neat to see the piston doing so many different things! That's what makes two-stroke engines so simple and lightweight.


http://science.howstuffworks.com/two-stroke5.htm
 
The reason I'm saying they fire at the same time is because it doesn't matter which plug wire you connect the inductive pick up of a timing lite to in order to check ignition timing. Either plug wire will do.
DAWG

just found out on other site both cylinders fire on both compression and exhaust stroke and if wires were long enough it would not matter where you put them
 
incorrect....

No Dawg, that is incorrect. The coil has two control wires on it that come from the MPEM. The mpem sends the signal to the coil on which plug is to receive that stored energy. There is no way you can take the MAG wire off and put it on the PTO and expect it to run. When the MAG plug is firing, the PTO piston is at the bottom of the stroke, preparing to compress it's fuel. Look at the research and if you like, follow that web link. They have an automated 2 cycle engine in motion so that you can actually see how it works.

Robin, you are correct. Both cylinders fire on the compression/exhaust stroke. But only one cylinder reaches that critical point at a time. Therefore, you cannot spark both cylinders at the same time.

You can take both plugs out and lay them on the engine. It's easier if you roll it over by hand, but spin the motor over and watch the plugs. You will see that they do alternate their spark.
 
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No Dawg, that is incorrect. The coil has two control wires on it that come from the MPEM. The mpem sends the signal to the coil on which plug is to receive that stored energy. There is no way you can take the MAG wire off and put it on the PTO and expect it to run. When the MAG plug is firing, the PTO piston is at the bottom of the stroke, preparing to compress it's fuel. Look at the research and if you like, follow that web link. They have an automated 2 cycle engine in motion so that you can actually see how it works.

Robin, you are correct. Both cylinders fire on the compression/exhaust stroke. But only one cylinder reaches that critical point at a time. Therefore, you cannot spark both cylinders at the same time.

You can take both plugs out and lay them on the engine. It's easier if you roll it over by hand, but spin the motor over and watch the plugs. You will see that they do alternate their spark.
I know i can be wrong but can you be? we all can be some time.
 
Dusthawk's Ski Won't Start

I'm still real sure about the spark plugs firing at the same time but I'll wait till I've got some facts before I got back to that. Now...........
Dusthawk,
The next time you get a chance, see if you can feel air huffing up thru the carb while you are cranking the engine. This would be a sure sign of a rotary valve problem. A rotary valve that is not correctly timed or not turning at all usually causes air to come back up thru the carb.
DAWG
 
Amazing....

I'm just amazed.....truly amazed.
Good luck to the start problem.....I hope you get it fixed soon. I know you've been working on it for some time now..........:hat:
 
2cycles....

I've been a owner/mechanic for 30 years. Right now, my primary business is the Seadoo watercraft. We do have a few Yammers here, but mostly Sea-Doo's.
I've been reading and keeping up with this post in hopes of helping Dusthawk out. Reading, trying to eleminate problems as he checks on them.
But at the moment, I'm watching this debate on the operation of a 2cycle and 4 cycle engine. This is rather funny!....
Dennis, I hope you follow up on your reading about the 2cycle engine. I've read several of your post and I think your a pretty good mechanic, just by what you've written. But your idea that one coil provides spark to 2 plugs at the same time......:confused:
 
it is hard to beleve this engine sparks at tdc and bdc. I would have thought it would back fire through carbs but i have been talking to a few experts and they all say this is how it is. I am still learning 2 cycle engines after 20 + years i guess there is still a lot more for me to learn. thanks for all of your help. together we will all figure out what is wrong with this ski
 
Don't Worry

Hi Manicmechanic,
My primary business at the moment is also SeaDoos and I"ll research this in order to prove or disprove what I've said. I've currently got four 4tecs in my garage that I'm repairing but these won't help me in this 2 stroke ignition situation. I checked out the link that SEADOOSNIPE suggested but all I saw was a single cylinder 2 stroke internals spinning around with no information about ignition systems. I haven't read anything from you to prove me wrong either other than your opinion. I know somebody who's got a GTS and I'll see if I can access his ski tomorrow and check things out. Seems to me the easiest thing to do would be to reverse the plug wires and then see if she goes. I'll let everyone know how this turns out.

DAWG
 
not mine but it seem to to be wise. and as close to subject as I could find. what we are all trying to learn is called wasted spark. questions about spark timing is very common and here are some answers. The secondary coil is not in any way connected to the primary coil when current is passed through the primary coil it produces a magnetic field which induces current into to secondary coil this process is called mutual induction. The spark plug wires are actually either end of the secondary coil and as anybody with experience in electronics knows current needs a complete path to flow, so when the current is past through the primary coil and through mutual induction induces current in the secondary coil the current travels down one spark plug wire across the gap in the plug through the head through the gap in the other plug and up the other plug wire, thus making both spark plugs spark at the same time. So the spark plugs actually spark twice per revolution, however only one piston is on the compression stroke so only one cylinder fires the other cylinder just has a wasted spark. Yes you can swap spark plug wires and it will make no difference in running on a two cylinder.
 
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Ok dont use WD-40 just plain old gas a teaspoon in each cyl. put the plugs back in and crank it over now if you get it to fire but not stay running it is likely fuel related ie pump /carb. Now if you get a backfire thru the carb or no fire at all it is likely timing now you must be sure there is at least 100 PSI. compression in both bores. Now you said it has good compression and good spark try this test and post reply.
 
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