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Discussion Starter #1
I'm at the stage now in my 900ss project of looking at carbs. The motor is a 944, ported & polished heads, hi comp pistons, ie cams. I've found an outlet which sells split carb kits, the 39s are c.£990, the 41s are £1580 (I'm in the UK) - the price differential seems pretty huge to me! I'm guessing with the work done the 41s are the way to go, but any alternative view would be appreciated.

Tia.
 

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My Monster has a similar engine spec; 944, HC, ST2 cams, gasflowed heads etc. and I can say the 41s work very well. I don't know about the 39s so can't comment on them.

I'm also in the UK but when I bought my carbs, the best deal came from the USA; V-Twin - Intake and Fuel - Carburetors and Kits - Page 1 - Power-Barn although it was at a time of a better exchange rate.

To add, try FrankMX in NL he has them listed at €1215 http://www.frankmxparts.com/epages/62910900.sf/en_US/?ObjectPath=/Shops/62910900/Products/1240
 

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If you are really going for it you should probably go for the separates on short manifolds, they work better with the revs the other mods provide.
 

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I don't think Cycleworks is carrying carbs anymore, not listed on his website. Since all US delivered FCR's come thru Sudco, everyones US price is going to start from their price list.
http://www.sudco.com/images/Sudco Price List.pdf

these are for the dual racked, the prices are about the same for separates.
016.670 41FCR-2 DUCATI+ $1,325.00
016.650 39FCR-2 DUCATI+ $1,220.00

These prices won't help much for Europe buyers, but I thought I would note the currents prices are high here too.
 

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FWIW I had 39's on a high comp 900 motor and they worked really well.
I now have 41's on a stock 900 and they work well too.
I think it all comes down to tuning and the tuner.
 

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I am also one of those guys who prefer a set of 39's to the 41's. This is mostly from my mentors (Bruce Meyers -BCM) preference being the 39's . I have a set on a couple of my own monsters and they are great. I would bet the price difference is you are getting the 39's at the old prices (went up last year) so they are probably new old stock at that difference in price. No brainer as I would take the 39's anyway but that's just me.

I have a set of 41's lying around the shop that if I ever get time I plan on comparing directly with my 39's both on and off the Dyno. IIRC the 41 's will be slightly stronger on the dyno but the 39's will feel stronger on throttle response, snappier if you know what I mean. Since I do not ride my bikes on the dyno as much as the road the feel of the 39's was more important to me.

I think Brad had done a similar test but it was different bikes in the comparison so not a direct comparison between carbs.
 

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a customer of mine, who was a fiddler and is now a good tuner in his own right, has had both and prefers the 41 as he feels they are less responsive from a closed throttle and as such he can get on it earlier and harder with them. whereas with the 39 he needed to be more cautious.

so a nice counterpoint in application variation from theory and what you think you should be wanting.
 

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Discussion Starter #12 (Edited)
Thanks all.

In my arse over tit way I already have the short manifolds, so splits are definitely the way to go. Looking at the links I believe Power-Barn & Frankmx are out of stock on the split kits. Trouble with buying from the States is that I'm probably paying 30% plus in postage & taxes which is a consideration - something else to look forward to when the UK leaves the EU!

I'll check with the UK guys, I've only seen the carbs advertised on the website so they may not even be in stock. This is their site in case anyone is interested:

https://www.motorcycle-exhausts.co.uk/Ducati_FCR--category--488.html

Ha, phoned them up & in fact they only have 2 sets of FCRs in stock, a set for a Triumph Bonneville & 39 splits for a Ducati so that kind of makes my mind up. From what they say they don't hold a lot of stock as they usually get a quick fulfillment from Sudco, but currently they're looking at the end of August for any new orders. World-wide FCR drought!
 

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Mine came with 41's and I've never ridden one with 39's, but I have gone bigger on many other bikes and I'll dare say carbs are a lot like cam shafts in that whatever you gain up top costs you down low. That said, unless you're planning to drive it wide open frequently 39's will likely be the better choice. It's what I'd go to if my 41's ever needed replacing.

Interested to know where people get the short manifolds these days, are they still being made?
 

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Mine came with 41's and I've never ridden one with 39's, but I have gone bigger on many other bikes and I'll dare say carbs are a lot like cam shafts in that whatever you gain up top costs you down low. That said, unless you're planning to drive it wide open frequently 39's will likely be the better choice. It's what I'd go to if my 41's ever needed replacing.

Interested to know where people get the short manifolds these days, are they still being made?
Malossi makes them. You want two of the "rear" manifolds. Ducati Intake Manifold 40mm Rear Cylinder
 
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Either are better than the stock carbs, and if there is a deal to be had, then jump on it.
Unless you have a 986kit, then both should be fine once you sort out the jetting.
Split FCRs should only be on track because you'll lose midrange with the short intakes.
Think of it this way: short intakes with split FCRs is similar to the FI arrangement. Add an ST2 or FI cam, and your carby will have a power profile closer to the FI, yet a few HP higher with 41s.

I ran pair'd 39FCRs on my track bike for many years. The bike was responsive, and pulled well for what it is. I've subsequently put them on my 900 monster street bike, and for some reason were not the drop in I thought would happen. After countless hours adjusting jets, re checking float heights, a set of thinner needles cleaned up the lean firing at low throttle. Since I never ran there at the track, I guess it was missed! EMT vs EMP makes a difference!

The Track bike is heading down a similar path: Split 41s, FI cam, high comp 904 pistons, ingitech module, Dyna coils. Since the engine has 40K mi, it's out getting new valve seats and some mild polishing. I'd expect 80-85ish Hp at rear wheel when all is finished. Unless you are going to drop 3K for MBP heads, drop an 1100 monster in it.
 
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