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Old 07-15-2010, 01:30 PM   #1
hillbillypolack OP
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Ducati Monster FCR carbs : worth it or ?

Been considering adding FCR carbs to my '96 M900 for a few years. The bike currently has J/E high comp pistons, open airbox and a Stage 2 jet kit in the factory carbs. Dyna coils and NGK plug wires round out the engine mods.

I'm sorting out the electrics (replacing the Kokusan ignition modules with an Ignitech Sparker) but have always had FCRs on the wish list as some final upgrades. The ignition module came about as a way to remedy idle 'hunting' on many occasions.

I've heard a lot of positives about the upgrade, increased throttle response, power etc. What I'm unsure about is if it'll make the bike more cold blooded during early morning warmups or if it will make the bike more fickle to tune.

Thanks for any input or advice.
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Old 07-15-2010, 02:05 PM   #2
gusanito
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Absolutely. Hi Comp pistons and 41mm FCRs go together, like ham'n eggs.
I put them on my '95 M-900 ~15k miles ago and it just transformed the bike. The bike was cold blooded previously, so I installed the Powerlet starter wire upgrade kit from Desmotimes. It makes a big difference in the startup.

George
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Old 07-15-2010, 04:38 PM   #3
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I put 39mm Keihin flatslides on my '98 Supersport and (along with open exhaust) really made the bike come alive. The downside was starting it early in the morning when it got cold out. No chokes meant I had to blip the throttle a bit to keep it going first thing. That, combined with the exhaust, made me a bit unpopular with the neighbors (I leave pretty early). If the bike is not going to be used ass a commuter I would say go for it without hesitation. If you plan to commute this might be a concern for you. That said, the bike, onc warm, ran flawlessly.
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Old 07-15-2010, 05:25 PM   #4
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Gawd Yes!!!!!

No brainer. You've got to do the 41's. You'll feel like you just got 10hp, but the reality is that it'll carb so much smoothers with awesome throttle response. Expensive, but probably the most gratifying mod I've ever done on any bike.
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Old 07-15-2010, 06:48 PM   #5
BrianK
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The only downside to the FCRs is the cost. Everything else is pure improvement, and significant to boot.

I don't find them cold blooded at all. Turn up the idle before starting (easy on FCRs). Open the throttle a couple times to work the accelerator pumps. Pull in the clutch and hit the starter (or kick, in the case of my Norton). VAROOM!

And for the Duck, do 41mms. 39s are fine, but you're leaving performance on the table. There is NO advantage to 39s over 41s on a Duck with 750cc or larger engine.
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Old 07-17-2010, 09:33 AM   #6
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One of my 900SS's has 41mm FCR's, pistons and Dynacoils, and the other (my FE) is stock with a jet kit. The FCR's transform the bike, with better power, throttle response, and they sound cool.
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Old 07-17-2010, 03:20 PM   #7
GuinnesS
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Quote:
Originally Posted by BrianK
And for the Duck, do 41mms. 39s are fine, but you're leaving performance on the table. There is NO advantage to 39s over 41s on a Duck with 750cc or larger engine.
Odd that, on DR650's the FCR 39 is an improvement over the 41, and that's with 650cc/carb vs 375-450cc/carb on the quack! err, I mean Duck.. Something about better air velocity at the lower end.
I installed a 39 on my DR which absolutely transformed the bike; everywhere. I can even lug 27mph in 5th.
I would love to try out a well sorted 91-98 SS properly set up w/ FCR's. Mileage must be dismal though, it is on my DR.
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Old 07-17-2010, 08:58 PM   #8
hillbillypolack OP
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Quote:
Originally Posted by GuinnesS
Odd that, on DR650's the FCR 39 is an improvement over the 41, and that's with 650cc/carb vs 375-450cc/carb on the quack! err, I mean Duck.. Something about better air velocity at the lower end.
I installed a 39 on my DR which absolutely transformed the bike; everywhere. I can even lug 27mph in 5th.
I would love to try out a well sorted 91-98 SS properly set up w/ FCR's. Mileage must be dismal though, it is on my DR.

I've heard rare instances where a tuner prefers 39mm FCRs on the bigger (900) Ducs. I think its that the velocity through the intake is the wild card. Of course the 41mms allow more F/A for the charge, but I'm unsure about why a 39 would (or could) be better for a high comp 900.
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Old 07-18-2010, 07:41 AM   #9
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FCR's are a good thing for a 900. Combined with the H/C pistons it's the tits! Another thing that was a huge improvement on my 900 was a lighter clutch hub with the aluminum Barnett clutch pack. It revs much quicker and is quieter to boot. I wouldn't do the clutch and lighter flywheel for a street bike, you need a bit of inertia for smoother take offs.
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Old 07-18-2010, 09:50 AM   #10
gusanito
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41mm on the V2 heads and 39mm on the W2. The V2's, '97 and previous, IIRC, had bigger valves.

George
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Old 07-18-2010, 12:06 PM   #11
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I would go 41mm on an SS but look at 39's on a Monster. It depends on where you spend the most time. Bigger carbs breath better at high rpms, smaller carbs flow better at low rpms. If you also have a big-bore in you future it may be better to just go big now.
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Old 07-19-2010, 06:15 AM   #12
10/10ths
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Yes....

I have 39mm FCRs on my '97 M750.

Best mod ever.

Do it.

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Old 07-19-2010, 06:59 AM   #13
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The 41mm flatslides will tranform the bike, but as you suspected cold-weather starting takes a bit of finesse. It's totally worth it. While you're at it, since you aleady have high-comp pistons, get the heads ported by someone who knows what they're doing (Doug Lofgren, Guy Martin, Mark Sutton, etc.) too and you'll be amazed! I had an M900 race bike a couple of years ago that had all of that same stuff done and it was a beast, huge gobs of torque through the midrange and a ton of fun.
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Old 07-19-2010, 03:47 PM   #14
10/10ths
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about the cold start precedure....

....don't let this scare you, I have high comp FBF pistons on my 39mm FCR Monster.

All you do is this: Twist the throttle and hold full throttle for one full second, release the throttle, and repeat one time.

Now hit the START button.

Bike will instantly fire.

I recommend the bigger ground wire from Desmo Times and an Odyssey PC680 battery. I have both and my Monster NEVER fails to fire first time.

Just DO IT.

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Old 07-20-2010, 05:19 PM   #15
BrianK
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Quote:
Originally Posted by GuinnesS
Odd that, on DR650's the FCR 39 is an improvement over the 41, and that's with 650cc/carb vs 375-450cc/carb on the quack! err, I mean Duck.. Something about better air velocity at the lower end.
I installed a 39 on my DR which absolutely transformed the bike; everywhere. I can even lug 27mph in 5th.
I would love to try out a well sorted 91-98 SS properly set up w/ FCR's. Mileage must be dismal though, it is on my DR.
I get low 50s MPGs on my 900SS with 41mm FCRs, 11:1 pistons, Dyna Coils, and a lightened flywheel. And I don't baby it. The high-comp pistons help (but required retarding the ignition 3 degrees and using 93 octane (R+M/2 method) whereas it used to be happy with 87).

Sir Chris Kelley on the proper "sizing" of the FCRs:


"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. "
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