Rotax 185 CDI Conversion...easy!

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Postby lazair3ca » Wed Jan 19, 2005 7:59 am

Ray,

George bought the same kit as you did. He paid 289 CDN plus 15% tax. About the same as what you paid. We have not found the individual parts. But he is throwing away the flywheel and aluminium case. We may find we need the flywheel to smooth out the starting. Have you timed the engine as they recommended with the strobe light?
Bill
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Postby rayjb60 » Wed Jan 19, 2005 12:06 pm

I don't have a strobe available, so I did not attempt to change the timing.

I was thinking of playing with the Timing, but because when I run the engine it seems to develop the same power as before, Im not sure if I have that much to gain by playing with the timing.

I would like to get the RPM measured and install a tach to see that the RPM's are about right, since it relates directly to the thrust produced.

As soon as I get access to a strobe and tach, I will check the timing as described in the instructions.

Let me know if your tests reveal any new info about the timing.
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Postby lazair3ca » Fri Jan 21, 2005 12:59 am

Ray,

We made a change today. A couple of days ago we tried to start the engine but all it did was kick back. Today George removed the old flywheel and we compared it to the new one. According to my measurements the old inserts in the old Bosch flywheel casue the spark to be advanced by 22 degrees when compared to the new (Ducati) flywheel. So we put on the new flywheel and set up the coil/points plate to the 1 mm advance suggested in the instructions. The engine does not kick back now and it runs out the prime. We have a fuel/carburator problem to fix now.
Todays weather was -18 degrees C, sunny and windy. We will try again tomorrow to see if we can get the engine to run for a longer period of time.
I think you should change the flywheel.

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Bill
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Postby rayjb60 » Fri Jan 21, 2005 1:32 am

Hey Bill,

Thats very odd.....I could have sworn that the placements of the magnets is identical, on both flywheels.

How do you get the centre hub of the flywheel out and realigned into the proper orientation on the new flywheel?

I also get the distinct feeling that the spark fires more than once per revolution, maybe thats why mine runs if its really off like that.

I'd be interested to know how yours runs, mine ran so well I didnt even expect there might be a timing problem.

I wonder if the electronics somehow adjusts itself?

If the starting kick disappears that would be great.

Did you get your kit from Wildfire?
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Postby lazair3ca » Fri Jan 21, 2005 8:41 am

Ray,

I'm working on George's engine(s) this week. He may have the second one converted by the time I get out to the hangar this morning. It is -28 here so we may not start it until this afternoon.

You can use a press to remove the center section of the flywheel. The three mounting bolts are not equally spaced around the wheel. One distance is longer than the other two so the flywheel will only fit on one way. I will send a picture if I get a chance. The old fly wheel has two keyways in it and we had to be sure it was assembled correctly. We may have a strobe by this afternoon so we can further refine the timing.

There is no kickback at all now. We checked the compression on the engines before we started and I don't understand how you could start your engine with the kick that we have. Unless you have far less compression.

More later.
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Postby rayjb60 » Fri Jan 21, 2005 10:53 am

So that centre hub is just pressed in to the new flywheel......really?

The opening for the hub on the new flywheel does not seem to have a keyed opening....am I missing something?

There is the key slot on the shaft and in the hub that I am aware of...is that what your talking about?

Maybe if I take the flywheel apart again and examine it, things will make more sense.

Is the hub attached to the peice on top with the 3 bolds throught it?
If so then it makes some sense then, as the hub is held in position by the 3 bolds

A a top flywheel photo would be great.....

The pictures near the beginning of this post showing the flywheels side by side show the spacing of the 3 holes relative to the magnet positions....

That extra hole near the hub may be some kind of timing or orientation mark....and the position is quite different in the 2 flywheels......maybe thats my clue.

My compression is great....the engines are only 4 hours total time.....but I do have the compression release that I use when starting.
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Postby rayjb60 » Mon Jan 24, 2005 12:59 pm

I took a close look at the two flywheels and the picture comparing the two, and you are right, they are different.

I measured the location of the reference hole and compared it to the original and it is about ~25 degrees ahead of the other hole.

This means that I will either have to advance the armature plate by that much or use the new flywheel.

Since at this point it looks like it will be easier to use the new flywheel, instead of drilling new holes in the armature plate, then I will use the flywheel.

Im looking forward to less kick on the startup.

Thanks for figuring this out.....I have no idea how my engine even ran so well, being 25 degrees out of tune, but perhaps the ignition is capable of adjusting itself.

I'll post an update after I have run the engines again with the change.

Ray
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Postby lazair3ca » Tue Jan 25, 2005 12:24 am

Ray,

You figured it out. I have been goofing off skiing, CASARA training, building extensions for the CSM toboggans. Tomorrow we try again to get the engines running. George has converted both of his engines so we can try them out. The last time it was -18 deg C. Tomorrow should be 5 deg warmer. We will use fresh fuel and preset the needle valves to the recommended setting.

The three bolts do hold the flywheel to the center section which is keyed. Our center sctions have two keyways in them. Be sure you use the right one. The three bolt pattern is not symetrical. One distances is further apart than the spread on the other two! So you can only put it together one way.

I do not know how your engine could run with the timing so far advanced.

I have posted some more pictures on the modified controls thread.

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Bill
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Postby rayjb60 » Tue Jan 25, 2005 12:14 pm

Last night I took the old flywheels off and put the new ones one....it was a lot simpler than I expected.

The hub is actually part of the plate with the 3 bolts in it and comes apart as one unit.

I did not have to do anything special to remove the hub and replace it on the new flywheels.....just the 3 nuts are remove and it comes apart easy, with a couple taps.

I dont know why they did not just make a new armature plate with different holes in it and keep the existing flywheel....it would have been a cheaper upgrade that way.

Seems like the coil is advanced 25 degrees more than the existing points timing, so that everything fires at the right time.

I will run the engines this weekend and report what I find out.....Im hoping the starting kick will go away.
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Postby lazairiii » Tue Jan 25, 2005 4:15 pm

Ray and Bill,

If either one of you have any way of checking the max RPM you are achieving with the newly installed CDI units, that will be a vital way of determining if the new CDI conversion is turning up to the range the points were turning. Remember the point were in the 5800-5900 range (variables here I know), but see if you can determine this if possible. Who knows, maybe it will me slightly better, that would be nice huh!

Thank you,
George Curtis
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