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1994 900SS CR, 2002 998 Trackbike
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Discussion Starter · #1 · (Edited)
1014451

I've owned my '94 900SS CR for a few years now. I somewhat naively bought the bike in 2016 as project, that slowly turned out to be way more of a basket case than i had hoped. Over the past few years it has forced me to become a (very) amateur Ducati mechanic, with lots of help from this forum.

So maybe the story is of interest to some other owners, and it's an excuse to save my pictures of the bikes history here.

The photo above is "early days". I don't have the photos any more, but pretty much right after purchase i had to replace the head studs (due to a hillbilly repair job by a previous owner), and i had the cracked head stock welded and the frame powder coated, which is i think the state of the bike in the picture.

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This repair in combination with the stock Mikuni carbs and airbox turned out to be a pain, the airbox was very difficult to remove or install past this brace. That, and a leaking valve stem seal, gave me an excuse to pull the engine again a couple years ago

Tbc
 

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So what are you thinking ? I’m a big fan of air boxes over pods or unfiltered air, but maybe a custom air box for easier service ?
 

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Discussion Starter · #3 ·
The recurring story with this bike is me half-assing the job, instead of doing a full restauration right from the beginning. Reason, other than know how and money, was mainly that i didn't have a real work space. The first time I stripped the frame was in a dirt floor garden shed with a headlamp.

The second time, i had a new job and the option to use the work shop (hangar) after hours

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Like i said, the airbox had to go, and that's a convenient excuse to install some FCR41s
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Bought in used condition, rebuilt, and installed with 3D printed filter adapters


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My dad made the filter adapters for me based on measurements that i emailed him. They have internal air passages just like the stock short stacks. I have no idea what the longer intakes do in terms of power, because my so far only attempt to Dyno tune the bike ended with the Dyno computer failing in the middle of the pull.

The battery tray is riveted together out of aluminum sheet, bent on a brake at work.


Anyway, the new work space was great, but it, too, had limitations. I couldn't really leave stuff out at the end of the night because they fix helicopters there by day. Which is why I, again, didn't strip and repaint the engine like i wanted. I just fixed the seals, put the carbs on, and dropped the frame back on it.
 

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1994 900SS CR, 2002 998 Trackbike
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Discussion Starter · #4 ·
So what are you thinking ? I’m a big fan of air boxes over pods or unfiltered air, but maybe a custom air box for easier service ?
I went with pods mainly because it was easy, and because the flat slide carbs shouldn't care as much as the Mikunis probably would. I haven't noticed any disadvantages, and it sure is nice to be able to pull the carbs without even removing the battery
 
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1994 900SS CR, 2002 998 Trackbike
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Discussion Starter · #5 ·
After installing the FCRs, the bike actually ran pretty well. I had previously also installed an ignitech TCIP4 ignition due to one of the stock CDI units failing.

At this point I was riding the bike, but i still had the feeling that it could be "better", so there was a year or two of smaller incremental upgrades or changes.

Most importantly, i re-valved the forks with some new racetech gold valves
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And had the same done to the rear shock, along with appropriate springs front and back

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The bike came to me with some 11:1 FBF pistons installed but no other supporting mods, and thus required 94 octane gas or it would ping. The TCIP4 enabled me to dial back the timing a few degrees, and it really helped with the smoothness at lower RPM as well.

I wanted to try out some of the other features of the TCIP4, so i bought a throttle position sensor kit from Liam Venter in NZ and made a 3D ignition map
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This is where i really should've been on a Dyno - this map is basically just made up on the spot. I think it is fairly conservative, but no gurantees. It definitely leaves performance on the table.

To be able to get more than 36° advance at part throttle, one needs a flywheel with a longer lump, or another way to trigger the ignition. Brad graciously sent me this one that he had modified years ago while playing with these bikes
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Note the elongated trigger area at the bottom above the text.

I also relocated the oil cooler above the horizontal head, using a valve cover from a monster
1014454
 
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You couldn't find something less industrial looking? Yea it has a convient large handle but......

Oetiker clamps would also seem better
 

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I like the filter adapters. It is a huge convenience.
 

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1994 900SS CR, 2002 998 Trackbike
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Discussion Starter · #11 ·
You can't see the fuel valve, it sits behind the CR fairings when they are installed.

And yes it was held on the line with ty-raps in that photo, because I didn't have the right size clamps handy. That was a temporary thing so i could run the engine. It did work though.
 
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Discussion Starter · #12 ·
As you can see in the last photo, i changed my work space again. I finally moved into a house with my own garage last year, which greatly improved my working conditions when playing with my bikes. I got a lift, and most importantly i now have my own space accessible 24/7.

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The next step was to try some adjustable cam pulleys. Besides wanting to learn about cam timing, reason was that I had a stock pulley on the vertical head that had a non-removable lip on it. Which meant i had to take off the fixed and mobile tensioners each time to be able to wrestle the belt on there, especially with new belts this was very tight.

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The pulleys are from a later model Ducati. I had to machine the back side flat to get them to fit.

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Phasing the cams made the second biggest difference to engine feeling behind changing the carbs. Engine vibration was cut down significantly, and the bike will suddenly putter around town at 2,500 RPM smoothly if i want to, while it needed at least 3,000 before.
I wasn't sure about valve to piston clearance with my FBFs, so i only went to 110° centerlines on the cams. No significant change in the torque curve by my butt-dyno, at least nothing i could tell over the fact that the engine is just so much smoother.

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At this point I was very happy with the bike. Suspension and engine seemed sorted out, it would start every time (i did install upgraded starter wiring as well), sound great with the Hawk carbon cans, and was generally a joy to ride. Of course I would've liked lighter wheels, but whatever.


Then it started to burn oil again...
 

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Discussion Starter · #14 ·
At the end of last summer, i stuck a borescope down the vertical cylinder head and it didn't look great in there. For having only done 2,000 miles since I had changed the seals and cleaned the piston top, it was very black and carbon covered, originating from the exhaust valves. Additionally, i had reached the end of my shim kit when adjusting valve clearances - the valves where sunk so far in the seats that i didn't have any larger closing- or thinner opening shims.

All of those are indications of what i long suspected: that motor had a lot more miles on it than the odometer claims (which says 11,500 presently). The valve seats had probably been re-cut poorly at some point. And the valve guides were probably worn out, causing the oil leakage.

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Leak down test done previously. 80/70 and 80/71 or so. "Not great, not terrible." Both whistling a bit out of the exhaust ports. With the already sunk valves, and now the repeated leakage at the guides, i decided i wasn't just going to lap the valve seats. Those heads want a rebuild.

The engine had to come out for the third time.
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I'm still not a mechanic, but this time i had my own garage where the bike could sit as long as it would take, so i would be able to do a more complete job, like i should have from the start.

This picture is from October last year, and i thought I would make a nice winter project out of it, and do things right this time, or at least "more right" than before.

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This time, i finally wanted to address everything on this engine, split the cases, refinish the exterior, take a look at that famous crank gallery plug, and rebuild with new bearings all around (in light of the condition of the heads this seemed appropriate).


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Eww.

When I took the vertical head off, I found a nice crescent moon shaped impression in the piston from where the intake valve had touched it.
The valve was still straight, and the mark hadn't been there last time the head was off. So i must've done this while reinstalling the belts when I still had the old pulleys, the ones that required me to turn the engine to roll the belt on. I was probably one tooth off at some point, and i turned it a little too far before noticing.

So now i "needed" new pistons. Besides that, the cylinders where in really bad shape around the outside with corrosion, and already had thread repairs done (not by me) on the tensioner threads. Previous owner must've had a big air impact.
And the horizontal fixed pulley was just plain seized solid on there.
What a convenient excuse to go to 944cc, right?

On the chassis front, I really wanted to get nicer wheels finally. And while the racetech fork was pretty decent, it still wasn't as good as the one on my 998. Since better forks and wheels mostly have 25mm axles, instead of the 20mm axle/wheel on the 900 carby, this was another case where it made sense* to get both at the same time.



*"Sense" is a relative term here. What actually would've "made sense" is to sell the bike 4 years ago, and buy a used K5 GSX-R or something with cash left over. Then again, here we all are...
 

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Discussion Starter · #15 ·
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Pulling the primary gear. In case anyone's wondering, the answer is no. This puller is not big enough, and snapped in half. I had to buy a much more substantial one and modify it to fit on there.

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Split.

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And here is the famous crank plug. Keeping up with the theme that this bike had all commonly known problems for the model, this plug is totally loose and about to fall out. Definitely confirms that it was a good idea to split the cases.

I sent the crank and rods to Ben Fox in the US, to be fitted with new rod bearings and balanced with a set of 94mm pistals.

This of course requires 94mm cylinders. Should I have my 92mm cylinders bored and plated, to perfectly fit the Pistals? Yes. But, as i mentioned, they were in very poor shape externally, besides at this stage i still had illusions of a budget. So when I came across an almost pristine set of ST2 cylinders on ebay for next to no money, i decided to try my luck that way.

ST2 cylinders are 94mm. As far as I know, they are the same casting as the 900SS cylinders, just machined differently. What is an oil jacket on the 900 gets filled with water on the ST, so various openings for coolant/oil passages are different. I had previously read about people converting them one way or the other, and at that time Andy Gerling in Tasmania posted a video on YouTube that showed the process ("turning water into oil" - Andy's motorcycle obsession)


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Drill through the wall and water jacket of the ST2 cylinder into an internal oil passage, then plug the outside hole with a grub screw. The water jacket is now an oil jacket. Close off a couple of openings on top with Welsh plugs and more grub screws. Fit the oil flow restrictors that go between the head and cylinder on the SS, as well as replace the outside water fittings with the oil fittings for the little external return lines. Done, supposedly. A quick examination on the bench shows that it all connects the same way as on the stock cylinders now, so it should work. Right?
 
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Discussion Starter · #16 ·
Once i had the cases stripped bare, i gave them to a local vapour blasting person. He had a garage full of 1970s and 80s Suzuki 2-stroke stuff, all looking like it was made yesterday, so i knew i had the right guy.

The heads went to J-precision in Quebec, a specialist for Ducati and HD head work. They offer all sorts of services from a basic service, up to a proprietary full CNC re-port of the heads. I went with the intermediate option of just having guides and seats changed, and the ports cleaned up with hand tools.

The heads were the first part to arrive back, fitted with slightly oversized valves and looking very nice
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I have repeatedly heard that these heads have poorly designed intake ports, that don't respond well to conventional porting (hence the option of a full CNC redesign of the ports). Julian convinced me that a conventional port job like this would still be worthwhile. The Dyno will eventually show if he is right, but in any case, at least it definitely looks better now in there.

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I'm gonna keep my long intake runners, which were polished and matched to the ports.

I also bought a set of cams from a 900ie model ("8J").


The cases were done shortly afterwards:
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Here I'm already pressing in some bearings and seals (using a home made shop press). In reality there was a huge delay before this step because my local Ducati dealer is not very good at getting parts orders right, or even submitting them to Ducati in the first place.

I bought a lot of the bearings and seals directly from SKF distributors, almost all bearings are pretty standard SKF with the exception of the mains (that are RHP).

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The crank came back from Fox with some big holes in it. I'm really curious how much of a difference this will make.
 

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Nice work!
 

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Nice write up. I’m following along religiously. You’re doing all the stuff I’d like to do, but better. Those heads look fantastic. I cant wait to see the dyno numbers. How much lighter did the crank end up after balancing ?
 

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Discussion Starter · #19 · (Edited)
Nice write up. I’m following along religiously. You’re doing all the stuff I’d like to do, but better. Those heads look fantastic. I cant wait to see the dyno numbers.
It took me a long time to get to this stage as well.
Really curious what the Dyno will say also, although I'm definitely not shooting for the moon with this. If i can get something in the mid 80s I'll be very happy. In fact, if it makes it that far without popping because I made a mistake somewhere, I'll already be happy.

I'm somewhat close to booking a Dyno session, the motor is actually already back in the frame. I'll post more photos when I have time in the next few days

How much lighter did the crank end up after balancing ?
I actually didn't weigh it before or after. Estimating from the size and depth of the holes, I'd say he drilled a couple hundred grams out of it though. He does offer knife edge and polish, as well as significant lightening as well but i thought that would be going too far.
 

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The bike will be easier to ride pulling out of corners with more rotating mass. I have a lightened stock flywheel for mine. It does seem like an extreme amount of metal removal for balancing though.
 
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