FCR 35mm Carbs or PWKs

Has any one been using the Keihin 35mm FCRs? How do they work? They are very expensive.
The JS flatslide PWKs are cheaper. I'm trying to decide which way to go.

Comparing the two is like comparing a Honda and a Chinese pit bike. You get what you pay for. Jim

I've been using FCR's for a bit. I really like them now as they're dialed in. The only downside is there is no choke or fast idle, so you have to be there with the throttle during it's warmup time before you can leave it idle unattended.
I have installed an accelerator pump as well for a little more oomph at roll on and quick blips of the throttle.
This was a pic I took when I first installed them last year... pipes haven't blued yet. Also I have a shiney new CNW manifold from Matt that I'll be putting in shortly with a built in balance tube.



JD

I have Private Messaged you, cyclepsycho

I am happy with my PWKs and after 4 years and nealy 25,000mile on them I haven't touched them except for a sticking float, just a tap fixed that, but the other carbies look great if you got the money, quility always cost more and I am not a rich person.

Ashley

I've used FCRs on several race bikes, but not my Commandos (yet). They were designed as race carbs, and as JD says, have no chokes. I never found that to be a problem. A couple of cranks on the throttle before starting squirts enough fuel from the accelerator pumps to start a cold engine, and a hand on the throttle keeps it from dying till it warms up a bit. All my experience with them is in warmer climates, so I don't know if they have problems in places with serious cold.

I do like their light throttle feel and great response, and will probably put a set on my street MK3 eventually.

On the other hand, I've also used new and old style Amals, Mikuni flat and round slides, and Dellorto carbs on my Norton race bikes with equally good results. The thin I really like about the FCRs is the very light throttle pull, with no risk of the slide sticking.

Ken

Ken, in which classes do you race with those carbies ? In Australia they jerks would be getting all wound up if you used them in an historic championship event. I'm always interested in classic racing where the rules are liberal. Our historic racing goes nowhere near history, yet we put ourselves into a straight jacket.

If you can manage to afford them, by all means go for the FCR's. Matt would not use them if they weren't cost effect. Yes, the PWK's cost a ton less and they work to some degree and some don't to some degree.
It has already been metioned and in this instance it is profound, that you will get what you pay for.

Another concideration is to run just one instead of 2. I do not know how it would fit or if two straddles the frame to fit. These big flatsiders are really efficient and meter mixture really well. I think you could campare a Mikuni 34MM flatside flatside to and Mikuni 36vm round slide for example, with the smaller flatside carb winning out. The FCR 35 with the pump would be all the better plus. I personally concider this as a valid option.

Make no mistake, dialing these FCR's in can be a challenge, but if you can work with Matt Rambo's experience, it should be basically straight forward.

Here is my throttle wheel. The FCR's screw is on the other side.

I would also think the FCR's would be a capitol gain for your machine.

As far as no choke goes, I have a big pumper carb and 2 or 3 throttle twists is all the enrichining I need for a first kick start. The other great thing is, if you need to walk away there is this great big throttle stop adjusting screw, you could almost call it a throttle stop wheel. This is not a fussy thing, just a turn or 2 and your are fine. As it warms a little, a turn or two back and you are back to the tick over of your choosing. Hands on? A little I guess, but these are highend units and the grinn on your face will offset any inconvenience you may have. To be honest, it's a no brainer.

acotrel said:

Ken, in which classes do you race with those carbies ? In Australia they jerks would be getting all wound up if you used them in an historic championship event. I'm always interested in classic racing where the rules are liberal. Our historic racing goes nowhere near history, yet we put ourselves into a straight jacket.

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Alan, I had FCR carbs on Supermono (aka Sound of Singles) bikes, one of the modern classes that our historic racing club, AHRMA, includes in addition to their vintage and classic classes. On my featherbed/Commando in classic classes, which require period carbs, I've run Amals and Dellortos. On my Nortons in modern twins classes I've run Amals and both round and flat slide Mikunis.

Ken

Hi!

another alternative is to put 2 Mikuni RS 34mm on. I did so and I am happy with them. they got choke and they got an acceleration pump.

My experience with them: less gas consumption, more power and quicker response. Costs? About the half of the FCRs.....

To find the right manifolds was a little tricky.

Now I use nitrile plate manifolds from Allens Performance [UK].

I use PM 03, center to center: 2" - plug and play for Commando.....here is the link:

http://www.allensperformance.co.uk/prod ... folds.html

chris

lcrken said:

acotrel said:

Ken, in which classes do you race with those carbies ? In Australia they jerks would be getting all wound up if you used them in an historic championship event. I'm always interested in classic racing where the rules are liberal. Our historic racing goes nowhere near history, yet we put ourselves into a straight jacket.

Click to expand...

Alan, I had FCR carbs on Supermono (aka Sound of Singles) bikes, one of the modern classes that our historic racing club, AHRMA, includes in addition to their vintage and classic classes. On my featherbed/Commando in classic classes, which require period carbs, I've run Amals and Dellortos. On my Nortons in modern twins classes I've run Amals and both round and flat slide Mikunis.

Ken

Click to expand...

Ken, I am in the situation where to race in historic races I need a log book and the bike will be checked against it at scrutineering. Alternatively I can try to find a modern class in which the Seeley Commando might be competitive. We don't classic racing per se, except for BEARs classes which are rarely run and usually heritage BEARs start off the same grid as moderns. I really like the look and concept of flat slide pumper carbs and I'd like to try them. Our rules pretty much exclude that choice. I just had the faint hope that someone somewhere had class rules which were flexible enough to promote development - perhaps a retro class ?
Our racing is all silly stuff these days, any classic bike over 500cc usually runs in a class with no upper capacity limit, so the 'historic' connotation is nonsense - 'big is better'.

We also had a 'sound of singles' class here in Australia which was excellent. The only rule was that the motor had to be single cylinder, so the class was very popular. The trouble was that absence of the 500cc capacity limit meant that the fast bikes were 600cc and nearly 700cc Japanese motors in aluminium road race frames. The big motors would not cop the rigours of road racing, many blew up and it became too expensive to remain at the pointy end of races. So the class collapsed. To my mind it proved just how good a manx norton is as far as reliability and speed are concerned. I really wonder how much some of the organisers know about racing. Historically in Great Britain, capacity classes were implemented with good reason. The big capacity disparity kills off the concept of a level playing field. Personally I don't really care what the other guy is riding in my races as long as it is the same general type of bike and of similar capacity within reason.

acotrel said:

We also had a 'sound of singles' class here in Australia which was excellent. The only rule was that the motor had to be single cylinder, so the class was very popular. The trouble was that absence of the 500cc capacity limit meant that the fast bikes were 600cc and nearly 700cc Japanese motors in aluminium road race frames. The big motors would not cop the rigours of road racing, many blew up and it became too expensive to remain at the pointy end of races. So the class collapsed. To my mind it proved just how good a manx norton is as far as reliability and speed are concerned. I really wonder how much some of the organisers know about racing. Historically in Great Britain, capacity classes were implemented with good reason. The big capacity disparity kills off the concept of a level playing field. Personally I don't really care what the other guy is riding in my races as long as it is the same general type of bike and of similar capacity within reason.

Click to expand...

I can see the problem with only one singles class. Here in AHRMA there are two classes, Sound of Singles 1, which is unlimited 4-stroke singles, and Sound of Singles 2, which now limits water-cooled engines to 450 cc and air cooled to 610 cc. The size limits for SOS 2 have changed over the years, unfortunately making one of my SOS 2 bikes illegal for the class, and making the other one non-competitive unless I build a larger engine. I can't really complain (but I do sometimes) about it. AHRMA are trying to keep the class competitive by changing the rules as new bikes are developed. Besides, I'm only fielding bikes at the occasional race now, mostly out of nostalgia for the "good old days", and for the chance to hang out with other m/c crazies.

Oops! Just realized we've hijacked yet another thread. Sorry about that.

Getting back to the topic, one of the problems I had with the FCRs was that they were only available in limited sizes as linked pairs. The jumped directly from 35 mm to 39 mm, with nothing in between. I've just checked a recent Sudco catalog, and they do have a 37 mm FCR available, which would have been perfect for some of the twin carb singles. However, they are only available as single carbs, not linked together as a pair, which would make them difficult to fit to twin carb singles and Commandos without fabricating special manifolds. I also note that they now have FCRs available with chokes, but only in 39 mm and 41 mm. Just the thing for that new 1007 cc street Commando, right?

Ken

lcrken said:

... On my featherbed/Commando in classic classes, which require period carbs, I've run Amals and Dellortos. On my Nortons in modern twins classes I've run Amals and both round and flat slide Mikunis.

Ken

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My favorite was Dellorto as supplied by Ron Wood. I used them on a customers racer. They idled so slow and steady and metered so smooth and steadily I couldn't believe it. The problem was the overall width. They had to be splayed apart and required modifications to the Commando frame. I ran extra long manifolds which work best on a race bike. But that setup wouldn't fit a stocker.

Me too, Jim. I ran a pair of 34 mm Dellortos from Ron on my 750 (standard stroke) in my featherbed racer for years, and was very happy with them. I did have to use fabricated manifolds that splayed apart enough for the carbs to clear each other.

Ken

Why would a FCR need an accelerator pump when it has one already ?

I think it was the Yamaha FZR1000 that got the first FCR kits,we split a set to go onto a race Ducati in the early 1990's,I ended up putting a set (41's) on a beveldrive in the mid to late 1990's when there was nothing off the shelf (used one off a XR600 and another off a Suzuki Goose iirc - 1 down and i side draft)
The FCR made the 40 mm Dellortos look very average including fuel consumption.
Unless you can fine tune them including the pump the gain can be wasted,they are very adjustable (they were a race carburetor)
I run a TM40 pumper on the DR,great carburetor also once tuned.
Fancy carburetors are fine but if not fine tuned are little different to a Ferrari with half flat tyres/tires.

Actually, not an additional pump, but rather a pump cover. Gives a better "charge volume"

I'm using a "Stealth" brand, now discontinued, but the Boyensen Quickshot-2 does the same thing.

http://www.boyesen.com/quickshot-2.html

I'm considering their Quickshot-3, which has an adjustable leak jet for fine tuning the "blip"

http://www.boyesen.com/quickshot-4.html


JD

I rode a bike with the JS flatslides and was very impressed. But haven't tried the FCRs. Are they really worth the extra $ ?

cyclepsycho said:

I rode a bike with the JS flatslides and was very impressed. But haven't tried the FCRs. Are they really worth the extra $ ?

Click to expand...

...for an otherwise stock 850 motor (but planning on future Stage 1 cam and port mods)?

cyclepsycho, I sent you a reply but it seems to still be in the outbox not sent, maybe a board issue

email me direct and I will answer your question and provide a pic

kahrcw9@gmail.com