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Bad luck with the air filter. After you've done a compression check, and if it's fine. Make sure the fuel vents in the tank isn't blocked and that there is no water in your fuel.
 

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Lots of good hints here so I do not want to confuse the situation but....

1. was this the first time you ran the bike since doing the studs?
2. did it oil plugs prior to you doing this work?
3. does it have good spark on both cylinders now?


If this is the first run since it was apart there is a chance the sand has nothing to do with the symptoms, In fact most of my customers who have a foam or K&N type filter (all pod types) and live on a dirt road will see sand in the airbox past the filter. Yes yours was excessive so sand was being thrown at the airbox but a clean K&N has larger pores than a dirty K&N so I would expect it. If the filter was not held tight or sealed around the gasket I also would expect more. The engine runs a great amount of suction with a open throttle so any dirt does see a good chance of passing the filter if the holes are large enough, hold the filter up to the light and you can see what I mean.

I agree on the leakdown test but a compression test is better than nothing, did you perform one after having the top end apart to have a base line? The oiled plug could be a torn valve stem seal or a bag ring from assembly (one member here installed a wrong ring size so what is the ring end gap?

Yes icing could have been the issue with the running problem, or oil fouling caused by ???
Install fresh plugs and check spark on both cylinders, most ignition boxes will either work or not ( there are many bad aftermarket boxes (not ignitec) so verify oem is good first). Something from assembly or prior may have caused the one cylinder to drop out and then cause that plug to fail but it should be easy to track down.

Save the FCR money unless you find a good used set for short money , if you need pistons or cylinders a big bore kit will fix that and is a bigger power gain anyway.

Pods will only change the fact you will not see the sand in the airbox as it will be inside the carbs/motor, if you drive on a dirt road/driveway then that would be my last recomendation or you will need to run foam pods and oil them more like a dirt bike (thick and tacky oil) which will require a jetting adjustment as it restricts some air as well. Likewise any aftermarket foam or gauze , if you ride dirt I would stay with paper filters as they offer the best filtration.

Take a breath and do a couple simple tests, this will tell you where to spend your time/money.
 

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I'm still blown away that someone in Canada road a motorcycle in January!! Props!!
I just got back from the Vancouver Motorcycle Show, lots of people there taking advantage of the "Free Motorcycle Parking".
They even had Steve Baker there with a TZ750 powered "Street Tracker" doing demo runs for the crowds. 130 two-stroke horsepower on wet pavement......FUN!
 

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Discussion Starter #25
Ha, carb icing is definitely a possibility! How did I not think of that, I work in aviation and deal with this all the time.

It was about 40F and 100% humidity in rain, doesn't get any better for icing. On top of that the water going into the leaky airbox. Also, I did stop for gas on the way home, limping into the gas station trying to keep the engine on, but it started up fine right after that. Ice would've melted during the stop and then come back shortly after.

So ignition and possibly carb icing are the main suspects for my problem. Since I wanted to get an ignitech anyways (the bike has 11:1 pistons but stock timing, unless someone has messed with the flywheel), I will do that and go through the rest of the ignition as planned.

Definitely getting an oem filter as well. I don't ride on dirt, but the roads are just dirty here in the winter. Salt washes off quickly in the rain (I don't ride on that stuff), but the sand stays around longer.

The bike is back on stands for now and I'm fixing a few other issues, so it'll be a little while before I ride again. I'll update when I have some results from the compression test though. Unfortunately I don't have a base line, but if the sand really did wreck the horizontal pot and caused the wet plug, then I should see a big difference in numbers I guess.
 

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... The only thing is that pod filters are probably also not great in the wet I'm guessing, or is there a good workaround for that?
Not riding in the wet should work.

Seriously, what a fucken hassle, I hate doping a bunch of stuff to a bike then having to do it all over again, that's usually when I spit the dummy and it gets sold lol
 

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Discussion Starter #28
not riding in the wet is probably an option in Adelaide, not so much on Vancouver island though...

I knew this thing was going to be a basket case as soon as I got a closer look at it, so I won't get too frustrated - until it doesn't run in the summer. At least every time I have to rip it apart again it gets a little easier.

I just need to find a solution for the airbox. I had the dreaded frame crack near the steering neck, so I had a brace welded in behind the head tube. It is positioned so the stock airbox still fits. Except now you can't actually get it in there without removing the top half of the airbox, then putting it back together once in place. Re-assembling the airbox with all the little screws behind the head tube and that cork gasket in place is a massive pain. It also just occurred to me that the lid might not actually fit anymore once I have the proper (thicker) air filter on there.
 

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So - lived in Vancouver 'way back in the late 70's.
Beautiful place! "Warm winters"!!
Certainly agree that the environment is ripe for carb icing.
The European 900 SS's had a special design for than.
Attached is a shot of my old 860 back in the bay.
I'm sure yours will get fixed.
 

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FCR's don't ice up... ;)
 

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None of my carbs ever ice up because unlike some of you I’m intelligent enough to not ride when it’s cold . ��
The mountain passes are where the curves are, bringing a little cloud effect moisture down with the wind-chill factor into the range where you got the icing on the OEM carbs. Sure, its 90 degrees F when I left the house, but 20 minutes later it will be 30-40 cooler. And lets lay some of the blame where it belongs, the Mikuni carbs were never made to put up with that ethanol crap we have for gas now.
 

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Discussion Starter #35
I used to have a carbed SV650 years ago, I believe the carbs are the same. Only ever had carb ice once with it in about 25,000 miles, at least to the point where it killed the engine. That said, the time it did happen the conditions where similar to my trip last Sunday.

I have the carbs out at the moment for cleaning (again). Little bits of sand under the diaphragms and everywhere :[

There are small cracks starting on the outside edge of the rubber, so I ordered new diaphragms too.


Has anyone here had Mikunis with the "factory pro" kit in them?

Mine have the FP nickel emulsion tubes and a titanium needle installed. The jets say 130 on the main (wouldn't stock be 140?), 70 on the choke jet and 40 on the pilot.
Some research tells me the FP jet kits came with 127.5, 130, and 132.5 main jets - so, leaner than stock? That seems unlikely. Or do they just use different sizes due to the different emulsion tube ?
 

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Main jet is stamped with orifice size, which isn’t a flow rating. However, those orifice sizes should flow close to the same. I have a Factory Pro kit in mine, don’t remember what size mains I’m using but it sounds as if the kit you researched may be for a different engine which uses those carbs but requires different jetting. At any rate, main jet size must be correct for the engine at wide open throttle or it will run lean at wide open throttle, though the correct needles and emulsion tubes will result in the right mixture at all other throttle openings. I wouldn’t rejet the engine based on what they sent me in a kit. Too rich is much better than too lean, if you’re trying to jet it yourself.
 

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Discussion Starter #37 (Edited)
The jet kit is probably from either FP or Dyno jet or something. I looked up the dynojet kits they sell for the 900SS carb models and they seem to come with anything between "120" and "150" main jets. All for the 904CC 2V engines.
Jet Kit Products for DUCATI MOTORCYCLES.
I found a reference to a FP kit that came with 127.5, 130 and 132.5 jets for the same motors but I can't remember where.
So that's my best guess as to how this "130" jet ended up in there.

So far, every time I pulled the plugs they showed signs of running rich (sooty base ring), and there are no indications of lean condition anywhere while riding either, including some short tests I did wide open.

Thats what has me wondering, how is this possible at sea level in near freezing weather, if the jet is nominally smaller than stock already.
Otherwise I'd just go back to the oem 140 and use that as a starting point.

I'll do some more controlled full throttle tests with new plugs once the bike is back together, pull the plugs immediately after, and go from there.
 

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with a std airbox lid the 900ss will be fine with a 130 main. they are on the rich side with a 140. if you go open lid or pull the snorkels you need a 145 or so.

factory pro use mikuni jets. dynojet use their own, which are smaller number for number. a 140 mikuni is around 150 dynojet.

if it is fouling plugs it's usually worn needle jets (emulsion tubes). if the factory pro needles are scratchy at all they'll tear up the needle jets very quickly, and any new ones you put in there too.
 

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Unfortunate

The stock airbox is very effective, I used a K&N with success. Most take snorkels out, I did and loved the intake roar.

The filter/intake should not pass dirt nor sand if properly installed.

Bob
Every time I get under the tank I adjust the snorkels to face more forward. Thanks for the tip, never thought to just take them out.
 

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In the US, a donor engine can cost between $200-300 shipped.

If I were you:

Millennium Technologies charged me $536.46 for 944 bore, plate, and shipping. You can find a set of healthy HC 94MM pistons on eBay (sellers such as Used Ducati Parts / Anglada, Ducati Depot / Eubank, etc.) for $300. Total is under $1k. Edit: I bet without enough time and patience, it would not take long to find a set of FBF 94s here for $200. They're $414.xx last I checked.

The motor must be dropped anyway. Why not add a few more hundred dollars for MT to bore and plate, and throw some 94MM pistons while you're in there? FCRs are meant more so for smoother operation rather than bolt-on power, but in any case, the HP/TQ-per-dollar of a 944 is incredibly more than FCRs. This is based on Brad Black's graphs and of course, anyone who first did a 944 mod and afterward slapped on FCRs.
 
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