Skidoo Rotax 447 bad spark - Snowmobile Forum: Your #1 Snowmobile Forum

bert · 01-19-2013, 10:19 AM

Hi
I am having trouble getting my 1990 safari to run properly. I have stripped and cleaned the carbs numerous times and changed the plugs. It seems to only run consitently on one cylinder. I changed the high voltage coil two years ago which did not make a great deal of difference. This morning I was trying to get it to run on both jugs but to no avail. I switched the plug leads around and the bad cylinder followed the leads.
Any ideas anyone?
Many thanks

**smallengineguy** · 01-20-2013, 07:37 AM

Coil is still bad. If it follows the cylinder, that eliminates the CDI or stator as the problem. Those 3 things are the entire ignition system. Try switching just the plug boots themselves?

bert · 01-20-2013, 03:17 PM

Thanks very much for the reply.
I stripped off the boot and cut about an inch off the plug wire and re-attached the plug cap. Now I am really scratching my head as it still only seems to be hitting on one cylinder at a time but both exhaust stubs are hot. It coughs and splutters and pops out of the exhaust. I do not know a great deal about CDI ignition but it appears as there is only one ignition winding on the stator both plugs fire at the same time, twice each revolution of the engine? Could it be that the sytem is just not giving enough power to fire both plugs and if one plug wire has a higher resistance it will favour the other plug?
Is there a way to test the CDI with it on the sled? Also how do I check the resistance of the stator?
Any help or advice is very much appreciated.

**smallengineguy** · 01-21-2013, 06:16 AM

You are correct on operation. If it did not have enough power, it would not run. You said if you switch plug wires, the dead cylinder will fire?

bert · 01-21-2013, 06:55 AM

Correct. After trimming the plug wire it seems that it will fire both cylinders but not at the same time. It will run for a second or two on both and then drop back to one. I cannot tell which one, if either, is consistantly missing. Both exhaust stubs heat up and both cylinders feel warm.

**smallengineguy** · 01-21-2013, 12:49 PM

Get an inline spark tester to see what side is dropping spark. If it's both, thhen time to look at a wiring issue with the sled itself (key/kill switches)

bert · 01-21-2013, 01:34 PM

I'll try to find a spark tester. I would think if it was a kill / ignition switch issue the sled would not run on one cylinder? Do the cdi boxes fail gradually or is it either working or not working? Same with the stator, could it be getting weak?
I really do appreciate the help.

**smallengineguy** · 01-21-2013, 06:47 PM

This is what you wrote above: "it seems that it will fire both cylinders but not at the same time." Unplug the harness from the engine while it's running and see if it still does it. If it does, then it's isolated to the engine. Spark testers are sold at any good auto parts store. CDI's are 99% of the time good or bad, period- no in between. Stator could be failing. DOes it get worse as it warms up?

bert · 01-21-2013, 08:37 PM

I will do as you advise. Yes it seems worse as the engine warms up.
Thanks

**smallengineguy** · 01-22-2013, 03:43 AM

It could indeed be the stator going out as it gets hot.

bert · 01-22-2013, 08:13 AM

I am trying to find some info online about the stator resistance but to no avail. I was looking at the wiring and of course it is all tucked down under the engine out of reach! I saw two small square boxes, one attached to the engine which I believe is the CDI, the other is attached to the chasis and I think is either a rectifier or resistor of some kind. Do the stator wires go directly to the CDI and if so do you have an idea of the resistance value I should be looking for?
Thanks again

**smallengineguy** · 01-23-2013, 03:43 AM

I don't have any values. If the coils are new, and it's dropping spark, I'd say it's the stator. I have values for newer sleds, but I think yours has different wiring.

bert · 01-23-2013, 06:13 AM

Thanks very much for the help, I am inclined to think so too.From what you say it seems to be the only component that would behave this way and of course is the most difficult to get at! I will keep digging around for the test values and post them if I find them. Probably not going to do too much to it today as it was -10f this morning!
Hopefully this storm on Friday will deliver some snow.
Happy riding.

**smallengineguy** · 01-24-2013, 03:44 AM

The problem is that if it's intermittant, it's going to measure good. Did you unplug the engine from the harness to check that?

bert · 01-24-2013, 06:29 AM

I will try that, the connections, of course, are under the engine and hard to get at. I felt that if it would run on one then it probably wasn't a kill switch or wiring short but I will certainly try. I tried starting it yesterday and apart from one or two hits it would not start. If I can get it to run long enough to get it into the garage I can go at it in earnest!

bert · 01-25-2013, 01:30 PM

I unplugged the harness but it made no difference. I took the carbs off again and looked at them, had the float needle checked just to be certain, it is seating well. I Can now get at the wiring a little better. There are two wires going to the CDI box, the other three go to the electrical system I think. Is it the two to the CDI that I need to put an ohmeter over?

**smallengineguy** · 01-25-2013, 09:49 PM

One wire set should go IN to your CDI from the stator, the other set of wired should come OUT of the CDI to the coil.

bert · 01-26-2013, 09:17 AM

OK, I see the two wires going in to the CDI box. Are these the two wires from the ignition winding on the magneto? I have been reading about ignition systems (I can almost hear you groan!) . What is a trigger coil and does this sled use them or is it just the two wires I need to measure resistance across?
Thanks

**smallengineguy** · 01-26-2013, 01:15 PM

The trigger coil tells the CDI when to fire based on timing. www.hlsm.com will give you a good look at the fiche for ignition. The trigger coil is under the flywheel with the stator.

bert · 01-28-2013, 06:01 PM

Thanks for the link to the microfiche, really great! On the fiche it just shows a generator coil and a lighting coil. No trigger coil. I only have 2 wires going to the CDI box. I finally got ahold of my Ohmeter (my 12 yr old had kidnapped it for a science project) and measuring between both wires coming from the magneto it read 52 Ohms. I then measure each against ground and one read zero and the other 52 again. I suspect one of the wires is a ground and the other is the other end of the gen coil. Does that sound reasonable? Either way 52 Ohms seems rather low for a magneto coil.
Any insight you may cast upon this is ,as always, greatly appreciated.