Flywheel / Alternator Tech

[Kato]

Because I've been asked about this a few times recently I thought I'd have a go at writing a bit of guide, there is often talk on this board of engine swaps, mostly people looking to transplant a 900 motor into their 600's, this is not usually a problem if you can find a 900 motor of the correct variety, the 1 question I get asked most often is
"can I use an injection engine with carbs"
The answer is YES, you just need to swap a few parts around, it’s not all that tricky to do, there are a couple of gotcha’s but also advantages the later motors use the 3 phase alternator, much better than the old single phase ones that keep cracking, a little wiring mod will be needed later but it’s not hard to do

1. Flywheel
2. PickUps
3. Case Oil seal for the wires

And thats pretty much it, the first task is to remove the clutch slave cylinder then take off the side case to reveal the flywheel assembly.

Remove the nut from the crankshaft and the flywheel will pull straight off, taking note of the alignment marked by the dot on the flywheel,

Now remove all the allen bolts to separate the alternator case from the flywheel, then flip it over to remove the sprag gear, this can be done by putting back a couple of the allen bolts just loosely on the wrong side and gently tapping them through the sprag will eventually come out, be patient it’s a tight fit.

I’m putting this one back together with a light alloy flywheel from CA Cycleworks, you don’t have to use one of these but it might be cheaper and easier then sourcing the correct part from the dealer, of course the advantage is your engine is going to pick up revs a bit quicker, or you can just swap the parts straight from the smaller engine.

Looking at the two flywheels there isn’t that much difference, I apologise for the crap photo, note the trigger on the alloy one, the main difference here is that the steel one on the left is just over 1lb or for those of you that speak French 534 gms heavier than the alloy one, a not so insignificant saving in rotating mass and in my opinion well worth the effort, when putting the assembly back together there is a little dowel that lines everything up, I only mention this because the last time I asked the question “is that a spare one” pointing to said dowel on the bench the was an eruption of expletives followed by much dismantling, more swearing and a lot of low flying spanners, use the dowel to get the sprag lined up and then with 2 or 3 of the allen bolt evenly pull the sprag into the flywheel, you'll need to take the bolts out after to put the alternator caseing on


So the flywheel assembly is back together and looking like these

It’s time for the most important part of the job............


The two assemblies in the picture are essentially the same, the only difference being the one on the left is fitted with a Corse lightweight alternator, to feed my fetish for all parts not really necessary for a road bike and probably not a good idea if you ride in the dark as they do not push out the power of the standard one, your lights won’t like it, that aside they are fairly easy to source S/H the problem is they never come with this bit and will never fit without it and of course you cannot buy that part seperately from Ducati

[Kato]

If you do deside to go the Corse route and can find the adaptor it fits in here..



Ducati haven’t significantly changed the casting for the for the 2v cases since production started, so that makes life really simple for us in this instance because we need to fit some pickups and even thought not used in the injection motor the casing still has the mounting points.


Here’s the first of the gotcha’s some of the later casings have the mounting posts but they are not drilled, no great effort to do just a pain as we need them to bolt these on.



The last bit thats going to catch anyone out is here..


The picture is a 2001 900 SSIE it had the blanking plug pictured, again there is a gotcha in that some of the later cases were not drilled at all, it is possible to drill and tap the hole, but you end up with not many threads as the casting is very thin, so I like to machine a top hat thread that and press fit it to the case like this.

Now we can fit the grommet assemble and thread the wires for the pickups, last bit to do before putting the outer case back on is to set the correct air gap should be between .6 and .8mm


Casing back on there is one last job to tidy it up, the injection motor has a pickup sensor poking out the side, I used to just leave it and tuck the wire up out of the way, get some very puzzled looks from people wondering why its there on a carb bike, it's an ugly bit of kit so I now like to make my own replacements



JOB DONE!

[Stafford]

Nice job Rob, have you seen the alternators on the bay? Any good for a track bike?

Great post! Thanks for this. Maybe you can help me ...

I took my alternator off at the weekend not realizing i had to note it's orientation with the crank (duh!). I see you have shown to align the dot to the notch on the end of the crank shaft, but which one it is as there are two? I guess it's the one that lines up with a key way deeper down the crank shaft? Do you know?

Cheers,

Chris.

[Kato]

Originally Posted by Stafford

Nice job Rob, have you seen the alternators on the bay? Any good for a track bike?

Stafford thats the ticket mate, just be aware you need to source the casing adaptor I can let you have a drawing to get one made, I've already asked that chap and he does not have them, Ducati only sell them with the full kit at about £400.

Great write up that very informative.
You might want to add this though. I did this conversion on my spare 620 engine and found out that there are two (at least) sizes of alternator windings/housing. The difference was only 2mm in diameter but the existing 620 windings would not fit into the 900 housing. I had to source some more windings.

[Kato]

Originally Posted by dr chris

Great post! Thanks for this. Maybe you can help me ...

I took my alternator off at the weekend not realizing i had to note it's orientation with the crank (duh!). I see you have shown to align the dot to the notch on the end of the crank shaft, but which one it is as there are two? I guess it's the one that lines up with a key way deeper down the crank shaft? Do you know?

Cheers,

Chris.

Which one do you have?

If its two yellow wires then its the older single phase in which case line the dot up with the woodruff key

If its the later 3 phase (3 yellow wires) look at the end of the crank you'll see it has one short slot and one slightly longer thats goes up onto the shoulder before the threads start, line the dot up with the longer slot.

Hope that helps.....K

[gary tompkins]

Top write up as usual

[900Rebuilder]

Does anyone happen to have a copy of this thread saved with all the pictures still accessible? Just about to get into this part on my build and this post is exactly what I need to talk me through the process

[Kato]

I don't even remember writing that :-)

[Kato]

What are you thinking to do ? happy to answer any Q's either post them or PM me

[900Rebuilder]

I've got a 900ie motor to go into my carbed frame (with loom and carbs etc) so need to make the "new" engine work in the old frame. I'll also be using an Ignitech ignition system as well if that helps or matters

[Mark64]

I fitted a lightweight flywheel to my s4rt, it made a huge difference in throttle response, I spoke to Nelly from cornerspeed about it, I said it only weighs 250 grams, he said 250 grams isn't a flywheel - it's a pack of butter!

[Luddite]

Originally Posted by Mark64

I fitted a lightweight flywheel to my s4rt, it made a huge difference in throttle response

I fitted a heavier flywheel to my Evo and it made it so much nicer to ride on the road with no noticeable loss of acceleration (perhaps because I lowered the gearing at the same time).

Horses for courses I guess...

[Nasher]

Originally Posted by Mark64

I fitted a lightweight flywheel to my s4rt,

Originally Posted by Luddite

I fitted a heavier flywheel to my Evo

For the sake of completeness, and balanced opinions, I have a standard flywheel in the engine of my M1000.

I've not noticed any difference.