Do I want 39mm carbs or 41s? 900SSs get 41mm carbs. 750s get 39s. You can put 39s on your 900SS but if you ever start really trying to get power from your motor, you'll need the 41s. Sudco, the US Importer of the carbs and who assembles the kits, says they sell 4 or 5 41 kits for every 39 kit. Also, the 750SS racer that Sudco was developing their kits on ended up running FCR41s. Switching from 39s to 41s got them a few more hp on top and added slightly to mid range power.
Some shops and "Ducati gurus" will say that FCR41s don't belong on a 900SS. Well... if they are your only local support and you might need to turn to them for help, then you'd better get the 39s. Why? If you turn to them and you've got 41s, with their closed mind, they will not be able or willing to make the 41s work right.
Consumer Alert:
Ca Cycleworks customers have warned about some "special deals" on the Internet for what would appear to be a full FCR kit, when said kits are without instructions, throttle, or cables (and at least once the manifold adaptors, too!) This requires another $80~$160 of parts to properly install these incomplete kits.
All FCR kits sold by Ca Cycleworks are shipped complete with carbs, cables, throttle, spigots, airbox adaptors, instructions, and air filter.
All Cycleworks FCR kits are verified to ensure the proper baseline settings.
For those who purchase incomplete kits used or from other vendors, Cycleworks can supply you with the support you need: proper replacement parts shown below, copies of Sudco instructions, and Ca Cycleworks "install hints".
Note that when buying FCRs from private individuals or from eBay, you may need to purchase manifold adaptors, calbes, or throttle, adding expense to the purchase.
What about midrange? I've heard that FCRs kill midrange... When referring to Ducatis, this is misinformation! The whole reason that this "wives tale" came about is from when FCRs were first introduced on the US market and people put them on GSXRs and other 4 cylinder Japanese bikes. Instead of calculating the best size for their application, they'd put 39s or 41s on a street 750 motor, when 35s are appropriate!
Gas laws say that the larger the venturi, the less velocity with an equal airflow. Engine tuners know that less velocity means less torque. The reason for huge aftermarket racing carbs is typically to allow for more velocity at high RPM with throats much larger than most OEM carbs. The same heads and same rpms mean that the airflow would be about the same and the "reasoning" that the carbs so dramatically "harm" velocity and torque on a 900SS are totally ignoring the intake tract, valves, and cylinder size. A Ducati 904cc V-Twin has cylinders with insane stroke and 452cc displacement each, while a 4 cyl 750 has 187.5cc cylinders with terribly short strokes. Further, the Japanese 4 cylinders also have more valve area with their 4 valve per cylinder heads. The Ducati has more displacement AND less valve area, meaning that the velocity through the intake tract remains high and the 900's great midrange torque is amplified by FCRs.
I've put FCR 41s on essentially stock 900s and was able to power-wheely in second gear at 40mph at 4200 rpm. You need a 39T rear sprocket for that trick. And when the revs pass 5 grand, you have to back out of the throttle so you don't flip over. Having a lightened flywheel guarantees 2nd gear wheelies.
Actual customer e-mail!
From: "Ron Perry" erdoc_1@hotmail.com To: Chris Kelley Sent: Friday, August 04, 2000 8:26 AM Subject: Re: got the carbs installed over the weekend. couldn't wait to try them out. in a word, FANTASTIC! all i ever wanted to make my bike complete was second gear wheelies. now, no problem. love it. thanks.Will I get tickets? Oh yeah you will. Consider this your warning, cuz you won't get one from the coppers! Sorry, Cycleworks won't subsidize your legal defense, just take the $$$ you save from buying here and save it now! :-)
From: Fred Sontag Sontag_Fr@Unisonindustries.com To: Chris Kelley Date: Fri, 16 Jul 1999 08:27:42 -0400 Subject: FCRs HOLY SCHMIDT!!! You weren't kidding about the FCR's! I rode it home last night and still cannot believe how much different the bike rides. I mean, it is an absolutely different bike. It sounds different at the exhaust (much throatier) and the new "whoosh" noise from the carbs is also very cool. It was pulling so hard when I took it out last night I had to take it out on the interstate to see how hard it really pulls. I got a reckless driving ticket for my efforts. The FCR's are MUCH better than I had anticipated. I feel like I have a brand new bike. Thanks for the kit, it's all that and a bag of chips! Fred Sontag
From: Jim V jimv@webspan.net To: Chris Kelley Date: Fri, 18 Sep 1998 23:01:35 -0400 Subject: FCRs Installed Hi Chris, I just wanted to tell you that I installed the FCRs the other day and WOW! They work just like you said...I'm very impressed with them. Although I haven't tried pulling it up in second yet, it definitely pulls the wheel up in first a lot easer. It took me about three hours after work and then I had to go riding till 12:30 at night... I didn't want to get off. Thanks again, Jim
I want the kit but already have a K&N air filter, can I delete it and get a discount? Yes, I'll offer a $18 credit to delete the filter from the kit. In order to get this credit, you must add the "Delete K&N filter from kit n/a DU-0900 $-18" item to your shopping cart at California Cycleworks. I previously had all FCR kits "drop ship" directly to the customer, but sometimes Keihin / Sudco are not setting them to their own specs! Now, all carb kits ship to me for calibration then they ship to you.
If I got canisters and the carb kit, would the carbs be jetted already? Bascially, yes. Since the carbs come slightly rich (an appropriate conservative setting), a few hp can be found with some dyno tuning. You may not feel it much though, as dyno tuning won't help torque too much - it's already a lot higher than before. You get the big grins from all of the increased torque. If you want to diddle with your carbs, here's a useful tuning guide. A lot of useful tuning info is also in Sudco's catalog: needle selection 151k tuning graphs 110k and slow air screw chart 135k.
Please note that if you ARE going to diddle with your FCRs, keep two things in mind. 1) RPM is meaningless. As shown in the charts, each circuit in the carburetor is about throttle position. 2) You'll never feel if the carbs are jetted too rich. You can pour enough fuel into the bike to make 110 hp and it'll feel almost as good as with optimum jetting. But, go and make it too lean and it'll feel like someone hit the kill switch. Example: if the needles are too lean for 1/4 throttle delivery, you'll be toting along at a steady speed at 1/8 throttle and give it some gas to speed up and it's like someone literally hit the kill switch. Then as you give it more gas, you climb out of 1/4 throttle and hit the 1/2 throttle range where the main jet starts helping out the needle and BAM you've got massive power.
I've got what I call the 70/20/10 rule. 70% of the people I sell carb kits to bolt the carbs on their bike and wheely into the sunset with a maniacal giggle never to touch their carbs again. 20% of the people will love the increased power but want to diddle about with the fuel screw or slow air screw to get idle "just right." Note that these two adjustments are easy to get to. The last 10% of FCR buyers seem all fubar'ed. They can see the potential for the carbs, but something just isn't right. They just need to take their carbs to a local shop with a dyno and pay them to make the bike and the carbs play together nicely.
The only modifications that I have seen to require rejetting have been polishing the ports in the head and the Staintune spaghetti system. I'm not sure if going to a 944 or 984 kit will require rejetting, but suspect it would. The stock mufflers flow as good as any slip-on on the market while still attached to the stock header. The stock collector is so restrictive that the performance from mufflers is almost evened out.
Base settings:
| Fuel screw mixture screw |
3/4 turn |
| Slow Air Screw | 1-1/2 turns |
| Float height | 9mm |
| Main Jet | 155 |
| Main Air Jet | 200 |
| Slow Jet | 60 |
| Needle | EMT |
| Needle Clip | 3rd from top |
I made a webpage detailing where these adjustments are.
What about the power differnce when compared to a jet kit in the stock carbs? I've seen claims of 80 hp from stock carbs and careful jetting, but mine with the Keihin racing carbs (FCR 41s) and aftermarket mufflers pulled much harder than theirs and also had a killer top end. To get big time power, you start with Keihin FCR 41mm carbs, a better exhaust system, and eventually bigger pistons and head work. Head work is ultimately the most limiting factor in the SS engine.
The cheapest way to get the most horsepower is with the FCR kit. If you're ever going to try and get as much horsepower as possible from your Duck, save the $$ from the jet kit and go for the carbs. I sell the carb kit for $789. Retail is anywhere from $850 to $1150 depending on who you buy from.
A jet kit goes for like $85, then you'll have to pay a shop 2 to 4 hours of labor to install it. Then, to get it right on, you'll waste a couple of hours on the dyno and rejetting. I usually charge 2 hours to install a 900SS jet kit and I charge 3 hours to install the FCR carb kit.
What will I feel or notice on the street? Basically, with a 39T rear sprocket and a Stage II jet kit, you'll just be able to pull 6th gear to redline and go about 135 mph. In a drag race, you'll be neck and neck to an average running CBR600F2, but will get left by any Kawasaki ZX-6.
Put on the Keihins and you'll be able to just pull redline in top gear with a 37T rear sprocket and go at least 155 mph. I found out that my speedo actually reads LOWER than the actual speed, so I may have been closer to 160. I was side by side with a zx7r and he was flat out. Now you're on the heels of 750s and well ahead of most 600s.
I put my FCR 41s on my wife's 900CR with only TBR slip-ons and we were able to easily pull 120 mph in 4th gear two up. The 39T rear sprocket helps with acceleration, but FCRs cure that tiredness 900SSs get over 100.
That's nice, but would this affect the bike's stop light perfomance and make it strictly mid to top end performance? Oh, I forgot to mention that the FCR kit helps the bike everywhere. The FCRs are such good carbs that they will sustain an idle as low as 600 rpm! I still keep mine at the factory reccomended 1200 rpm so it'll charge the battery. The FCRs let you ride the Duck like a Jap liter bike: bring the revs off of idle slightly and let the clutch out. The FCRs reduce the V-Twin's low rpm stall greatly and dramatically improve driveability.
Power? You can whack the throttle open about the time you cross an intersection and have the front wheel 4 feet off the ground before leaving the intersection.
They sound incredible! Any chinks in the armor?
From idle to 1/4 why does fuel (just a little bit) spray into the air box? The spray is from the power pulses that transmit upward. FCRs dump serious fuel. The accelerator pumps shoot streams of gas into the throat. Also, FCRs aren't meant to be horsed at a stoplight (or on the lift). To put that fuel to work, you need to be under a load and riding the thing. I can be idling at a stop and kill the engine by whacking the throttle open.
With no choke, how do I start my bike when it's cold? This starts with ensuring that your idle is still set to 1200 rpm (when warmed up) as recommended by the factory. Before starting, give the throttle a twist and let it shut. The accelerator pumps will throw extra fuel in the intakes to help richen the mixture for starting. You'll need to experiment with say, a short 1/4 opening or opening to 1/2 or full vs two squirts. Don't go crazy, eh? Some folks also find that they need to also give the throttle a slight touch when starting to help the revs come up. Basically, it's "feel" thing. Barring all of that, you can crank up the idle a lot and then back it down as the bike gets warm.
Where are the missing o-rings? "There are supposed to be o-rings for the grooves under the airbox adaptors." Nope. Those o-rings are for ram air applications only, namely 1992-1994 Kawasaki ZX7R and newer ZX7RR. The o-rings are available from a Kawasaki dealer or from Sudco.
Any questions left unanswered? E-mail me and I'll see if I can't answer them. For purchase inquiries, please visit www.ca-cycleworks.com.
