Coil Packs - Jetski

[audi321]

Hi all. Let me start by saying I don't know a lot about engines, but I can almost get my head around 2 strokes as they're pretty simple.

I have 'acquired' a jetski as part payment for a job I did and it's a non starter.

It has a Rotax 657 engine in it and after a bit of research it is from 1993/4. It's a 2 stroke with excellent compression and it turns over fine but just won't fire up.

I've narrowed it down to the coil packs as the spark is pretty poor (I've put new plugs in).

Problem is these coil packs are pretty scarce now due to the age and are expensive when I can find one.

So, my question is. Do you think I could use a coil pack from say a motorbike or something similar to try and get it firing, rather than spending a lot of cash on something which it may not be?

It's a 650cc 2 stroke, so only has 1 coil with 2 HT leads coming from it.

Any advice is appreciated! Ta

[Turn7]

Im pretty sure any coil with twin leads should work, but you do need to make sure the resistance is the same. IIRC, something like 3-5 ohms primary. Usually marked on the coil unit.

[blitzracing]

Try a bit of easy start just to make sure its not fuel before you get too involved.

[audi321]

I've tried easy start but I'm sure it's a weak spark as I've had the spark plugs out onto the head bolts and there's hardly anything there.

I've tried new spark plugs, new HT leads, and now I've plugged a coil from my motorbike into it and I got about 5 seconds of fantastic spark and then back to a poor one again. Really odd. So now I'm not sure if it's the coil or not.

I hate electrical problems as they're hard to diagnose! At least with mechanical problems you can SEE what's broken.

Back to the drawing board then!

[Turn7]

See if you can find some test data for your coils,basic resistance tests should tell. It could well be an issue with the pulser coil if not main coil.

[audi321]

I've downloaded the entire shop manual for it (300 pages!) and there's loads of info about testing resistance but I'm hopeless with meters and although I've tried to do some testing, I'm getting silly results and nothing remotely like the manual says I should.

[Turn7]

I know what you mean. Id try and find a cheap coil and try that first, then Id be thinking Pulser coil, then ignition box.

But I would have checked EVERY electrical connection first. Including the main earth points.

[blitzracing]

How do these syetems work? Are they switching 12 volts across a coil from a battery, a Magneto or CDI?

[Turn7]

I would iamagine CDI at that sort of age.

[audi321]

Hi it's a magneto

[Turn7]

In that case, my limited experience would suggest either the pulser coil or the main coil as previously mentioned.

[blitzracing]

Its always worth changing the condenser if its changeable and not part of a switching unit. Its critical for getting a correct discharge from the coil. If they go open circuit you get very poor HT.