Rotax 185 CDI Conversion...easy!

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Postby rayjb60 » Tue Jan 11, 2005 3:32 pm

My engines are only 4 hours Total Time, and I know how they feel when running at various speeds, so if there is any change, I will notice it.

Unfortunately I do not have an rpm on them, but it sounds like you will have this well in hand soon.

I'm expecting the change in smoothness to be dramatic at the low end of the RPM range, since I believe most 2 cycles are tuned for the high end.

The ignition advance/retard should make an obvious difference.

The new armature plate, being identical to the original has the same location for the lighting coil, so you would simply leave your existing plate, and lighting coil in place and substitute the new stator coil for the original black ignition coil. You will still have the same red external connection for your RPM gauge.

The black connector can be left in place as well, but you need to route the ignition kill wire from the CDI unit to this plug.

I tried to read the Ducati part number, since the sides of the aluminum shield are open, but the angle is to sharp to read, so I will take the unit apart, take some pictures, record the model number etc and post it to this forum.

The hard part will be to determine what the coil is, since it has no model/manufacturer markings at all.

From my understanding of the subject, the coil generates a voltage that is amplified by the CDI/Coil unit and also triggers the firing of the spark via the CDI electronics.

Timing is set by rotating the armature plate slightly.
Here are the instructions(right click and SAVE AS on the link): CDI Timing

More updates to follow soon. :)
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Postby lazair3ca » Wed Jan 12, 2005 8:21 am

Ray,

Thanks for the quick feedback.

You are right about the lighting coil we only have to move it to the new plate.

My question about setting the timing has been answered in the Tech Notes. We now need a stobe light to check the timing.

We have an optical tach at the hangar and I was able to measure my RPMs with it, 5600 on the left engine and 5800 on the right engine. Shannon mentioned that you should be able to get 5900 to 6000 (if I remember correctly) static.

We started to work on another pair of engines yesterday. Checked the compression and they were 74/80 and 80/80. But we could not get a spark. That is one of our main problems which we hope to correct with the CDI module. I assume we will be able to check the spark with the plug out and outer part of the plug grounded to the case and flip the engine over with vigor.

We may have a module this week.


Cheers,
Bill
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Postby lazair3ca » Wed Jan 12, 2005 8:24 am

Ray,

How difficult will it be to move the center of the flywheel from the old unit to the new one? The three nuts are for assembly that connect to the pull start dogs if I remember correctly.
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Postby rayjb60 » Wed Jan 12, 2005 10:47 am

Moving the old center flywheel hub over to the new one seemed like a good idea, but the 3 nuts on mine look well seated and perhaps a chore to get them off without striping them, so I'll just use the old flywheel.

Here is the CDI unit pic with the part number on it from Ducati.
Image
The wire outs are exactly as documented elsewhere in this thread.

and here is the original armature plate with the old Black ignition coil and the
lighting coil opposite it:
Image



Here is the same original armature plate with the new coil mounted where the old black coil used to be, and the old points and condenser removed.
I did not even have to remove the old armature plate to do it, so existing timing remains intact.
Image

Next I will put the old flywheel back on and find a place to mount the CDI unit.
Perhaps I can get a spark on my table top to confirm its functional.
More updates to come!
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Postby rayjb60 » Wed Jan 12, 2005 10:53 pm

The CDI conversion is complete, using only the armature coil and the CDI/coil unit from the kit.

I used the existing armature plate and flywheel, instead of the new ones included in the kit.

I pulled the engine starter on the kitchen table with the spark plug exposed so I could see if there is a spark, and I am pleased to report that it creates a good strong spark very easily.

With the original setup I had to put the starter vigorously to see a spark, but to my amazement I barely pulled it through a couple strokes and saw good strong sparks immediately.

I mounted the CDI/coil with a single bolt and lock nut through the engine mount bracket, and connected the new kill wire to the existing black kill socket so I can use the existing ignition kill switch plug.
Image

Now I just need to run the engine to confirm the timing is good.

With the original flywheel, I will be able to adjust timing if necessary, through the flywheel slots without removing it....another reason to use the existing flywheel.

I'll do the other engine, then set her up and try out the engines.
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Postby Guest » Fri Jan 14, 2005 8:45 am

Ray,

You are making great progress. We picked up two CDI units yesterday. I expect we will just mount the complete unit on the engine and see if we can get a spark on the bench. Then we will have to see how it runs. We did not try to run the engines before the conversion because we did not have a spark on the bench.
Testing it will be more interesting because the temperature has dropped almost 20 deg C since yesterday.
If I can post pictures I will documsnt our progress.

I like the way that you mounted the CDI unit. It should get plenty of air to keep it cool.

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Postby lazair3ca » Fri Jan 14, 2005 9:27 am

The CDI unit is not available through our local Ducati motorcycle dealer
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Postby ozzie » Fri Jan 14, 2005 4:30 pm

i read somewhere that all Rotax engines use ducati igniton parts so maybe local rotax dealer may be of use, ozzie
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Postby lazair3ca » Sun Jan 16, 2005 5:15 pm

George has installed the new coil and plate but he is using the old flywheel from the engine. It is installed and we have spark but the timing seems to be off. We have excellent kick but it seems to be too far advanced. It is harder to check the timing when you don't have points. I'll send pictures later this evening.
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Postby lazair3ca » Sun Jan 16, 2005 9:28 pm

George has mounted his CDI unit on the bottom of the engine. We were able to eliminate the box and just use a mounting plate. The mounting plate looks like the first picture to follow.

The CDI is mounted close to the bottom of the crankcase but there is room for air to flow between the CDI and the crankcase. Second picture

The full bottom view is also included.
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