Ok, I've been messing with this sled for 2 Winter seasons and I'm at my wits end. Last year I went through my 1978 Skidoo Everest 440E engine. I had bad seals and a lot of sludge in the engine. I cleaned everything up and at the time replaced the points and condensers. Last year I struggled getting the sled started. Once it started I had a lot of backfire. I've been playing with timing and now there is no backfire when the sled is running. However when I give it the throttle the engine will not accelerate. It in fact bogs down and will eventually foul the Magneto side cylinder.

I put on an inline spark plug light. Both side flash at about the same rate, however the PTO side is much brighter. The magneto side has a bright flicker about every 3 seconds and the engine idle will pulse when it does. I swapped plug position and the dim light stayed on the magneto side. I swapped coil position and the problem stayed on the magneto side. I checked the plug wires and both measure 1.1 Ohms.

While I messed with this I noticed that the Magneto side cylinder is not hot to the touch nor is the spark plug. The PTO side has a warm cylinder and plug as I would expect an idling engine to have. Then while running I pulled the Magneto side plug wire and the engine idle was much smoother. Reconnect it and a surge every couple of seconds returns. When I pull just the PTO side plug wire while running the sled gets a terrible idle and stalls about 5 seconds later.

So I know I have a problem with the Magneto side. Swapping plug and coil positions did not change the condition. Could it still be timing? When I adjust the timing I am using the continuity beep on my multimeter and lining up the flywheel marks with the engine block as instructed in the manual. I am also instructed to have the cam fully advanced. The manual instructs me to rotate the engine in the normal clockwise direction and the points will just start to open and the continuity will interrupt when the timing marks align.

When I set the timing up during the engine rebuild the magneto side did work this way. However the PTO side would only interrupt the continuity if I rotated the engine backwards i.e. counterclockwise. Now with the engine in the sled and having changed coil position the situation is reversed. I have to rotate the engine backwards to get the magneto side points to interrupt the continuity beep. Does this make any sense?

I was thinking that the coil was bad but the problem repeats with swapping coil position. Is there a polarity on the coil so that when I swapped position it is working against the norm? A coil is just a DC transformer, so I have a hard time believing there is a polarity to it. Could I have a cylinder that is somehow electrically insulated from ground and that is causing problems getting the spark plug grounded? Could this all still be timing problems? Is the magneto having problems? I have a lot of questions and no answers. The sled is as old as I am so I don't have a great history on how to make it run.

PLEASE Help!!!!!! :bash:

It sounds like you may have a bad condensor connected to the points on the suspect cylinder. Keep in mind also that the breaker points need a reasonable amount of dwell (closed time) to adequately saturate the primary coil. The point gap will affect the timing difference between cylinders and advancing or retarding the breaker plate will affect timing on both cylinders. Ignition occurs the moment the points open as the voltage to the primary coil is cut and the field colapses inducing high voltage generation by the secondary coil.

This may be of no use to you, but several years ago (before I got into the snowmobile hobby) I did some work on a late 70's SkiDoo. When I changed the points and condenser I managed to install part of the ignition system incorrectly. When I was finished the sled would run, but not very well. It would not even rev high enough to engage the track. When I took it back apart and corrected the issue, it ran great.

I do not remember my problem exactly, but I believe I had something reversed, causing the timing to be about 180 degrees off.

This may not help any, but it is a perspective that you may not have considered, good luck.

C20Z24 it sounds like 180 degrees out of phase would be a condition where the points were hooked to the wrong cylinder. I ran that test down last year and made sure that the TDC on the correct cylinder is when the points open and the spark occurs on the correct side.

Thumbdoctor, I kept the old condensers and could re-install them. I am starting to think that I could be tracing a ground problem after some deliberation with a couple folks. What I am thinking about is hooking an oscilloscope on to the leads from the magneto to the coil. The wires are spliced to a connector where the kill switches are wired in. (I already tried disconnecting the kill switches to make sure it was not a ground problem there.) Anyway I can collect and plot the two cylinders on the scope and help determine if the voltage is the same and if there are any phase problems with the signals. At the same time this will also help determine if I have a condenser problem. If I understand capacitor discharge correctly should help steady the abrupt opening of the points to enhance the break of the circuit. Does this sound appropriate?
:unsure:

HMMMM..... This thing is really getting confusing. Last night I had the situation again where I had to turn the engine backwards to get the continuity tone to break on the multimeter on the magneto side. The PTO side was normal. Then I unplugged the coil and presto it switched sides. I had to turn the engine backwards on the PTO side to get the continuity to break, and the magneto side was normal. I reconnected the coil and the problem did not repeat. BUT I also noticed that when the points open and close on the PTO side I am getting a continuity break when I am checking the magneto side. This seems very odd. Almost as if the discharge of the condenser PTO is affecting the magneto side during saturation. The continuity break could be causing the Magneto side condenser to partly discharge as well as affect the efficiency of the coil. I could potentially have a floating ground on the timing plate or EMI on the coil pickups between the two cylinders. Can anyone give me a hey or nay on my thoughts.

More useless information...
In my experience as a chainsaw mechanic, I discovered that the condenser is not really needed for the operation of an engine. Their primary purpose is to prevent the points from arcing when they open. The points burn up much faster without a functioning condenser, but it may help for troubleshooting if you suspect this is the problem.

Have you considered changing over to an electronic ignition? Kits are available for many older sleds, although I have not tried any. The spark advance is built into them, which eliminates all moving parts. I have not found a kit for my Sachs one-lungers or I would have already converted over.

Last night I disconnected the condensers and tested them. Both measured 0.24 microfarads. The old condensers both measured similar values. I am going to get the oscilloscope from work Friday and see what I can do with it to diagnose the coil pickup signal. Hopefully they will both be a smooth sine wave with the peak of the left at the trough of the right. I also hope the amplitude will be the same. I tried using the min/max feature on my multimeter and turning the engine by hand. The bad side generated a max voltage of 0.78V. When I tested the good side I got an OL when testing the coil leads. I would not expect the coil pickup voltage to be out of range on my meter. I will see what the scope says.

Did you use Bosch ignition parts all the way through? If not, throw out the after market stuff and get all Bosch stuff. I have many headaches with aftermarket electrical components.
I am sure you are aware of this but, the secondary coils must be connected when you are setting the timing.
It won't be a ground problem to the cylinder unless you used fibre washers under the head bolts. Make sure you chaeck all the low voltage wiring from the points all the way through. You could have a bad spot in the insulation someplace that is leaking to ground. You could also have a bad ground connection on the secondary coil somehow.
Also,you could have a bad connection between the plug wire and the coil as well. The srews inside the plug wire connection on the coil or the plug end could be a problem too.
The breaker point ignition systems did not generate a huge amount of spark like electronic ignition so it sometimes doens't tyake much.
I am sure you have tried this too, but try a different set of plugs. I have had brend new ones fail.

Good Luck!

when you put an ohm meter from ground to the external coil side of the points & open & close the points what is the result on each? should you get a clean break in the circuit when the points are open I am not 100% sure that is why I ask?

On another note I have seen 2 bad internal ignition coils this year , could maybe be your prob? is there any sign of wear on the magnets in the flywheel? it doesn't take much play in the end bearing to skiff at high rpm.


Just a few thoughts.....

Well.... I put a digital oscilloscope on the coil pickups to see if there was a problem with the signal being sent to the coil. Indeed there was. Attached are the pics. Notice in the first image the blue line has a cyclic high/low wave after the points have closed, while the pink line has a hard steady grounded line when the points are closed. This bouncing was allowing leakage in the circuit and reduicing the spark on the magneto side.

Upon further review of my points that have less than 2 hours on them were oxidized with white corrosion. I cleaned them with some 600 grit sand paper and polished it with a dry polish wheel in my dremmel tool. I also noticed that there is one nice black pit in the contact surface. I got these points last year when I was rebuilding the engine. I had the timing off last year and a wiring problem that was grounding the magneto pickup to ground. Between the hour or two that the engine actually ran last season while trying to troubleshoot the timing and wiring problem, the points oxidized. The off-season may have also had something to do with it.

Anyway the sled started on the first pull and has a bunch of power. Notice in the second picture that the lines now both have steady grounded line when the points are closed.

Now if Indiana only had some snow. It was 70 degrees F here on Tuesday. It is back down to 35 now. No snow in the forecast either.

good to here you got it

Devo