Keihin FCR 39 H for triple?

Paul LeClair

Paul LeClair

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Calgary, Alberta, Canada
well, I spent a couple of years figuring out how to make Mikuni RS 36's work on my 84 RGS "1200", and I have missed out on a number of eBay auctions for used RS 36's, and run up against a number of U.S. based eBay vendors of used RS 36 carbs who won't ship to Canada, all of which got me thinking about just buying a new set of RS 36's, but that will easily be $1,200 +

so, I got looking at alternatives, and the Keihin FCR 39H flat slide looks like possibly an even better alternative for my 79 1200 than the Mikuni RS 36... As I already know how to setup RS 36's for a Laverda triple, I figure I might as well broaden my knowledge base :D

three Keihin FCR 39's brand new with adaptable linkages looks like they would be about $1,000 or so, the set of three intended for a 90's Triumph triple might even be closish for jetting and setup?

or "easy" enough just to start from scratch, although I have forgotten bore intake spacing centers and can't find my notes from setting up the RS 36's.....

I figure if I just found a Keihin FCR 39 setup for an air cooled two valved engine with similar individual cylinder volume, that jetting/needle/slide setup should be closeish as a starting point for a Laverda triple, seems simple enough... :-\

is anyone presently running Keihin FCR 39's on a Laverda triple? With what result?

Paul LeClair
 
you can buy RS36 carbs brand new for $789
I have been buying new sets from APE in USA

http://www.kzzone.com/carbs.html

There is also a vendor on Fleabay selling them at $748 brand new
Makes more sense buying them new at the moment as opposed to second hand

 
Hey Red, it's a shame to waste the spare carb off each set of 4. Have you tried building 4 sets of Lav triple carbs from 3 x 4-carb sets?
You'd be missing an accelerator pump and cable quadrant which you'd have to buy in as spare parts.

Cheers,
Cam
 
have looked into trying to build banks of 3 from the spare carbs
priced the parts I needed from Show & Go, was cheaper to buy new sets of carbs.
That bunch of idiots are another set of total tossers, what a joke of a business

was as far as I went, had other projects on the go

normally don't get a spare carb per set anyway, works out closer to 1/ two sets as the other gets raided for parts to repair damage found on the second hand carbs
is why I've gone to new sets at the moment while exchange rate is good

 
yeah, my first used set of RS 36's were no bargain, cheap to buy, expensive to fix and setup, especially in matters of time invested.

for the eBay used sets, the honest sellers at least mostly list what is wrong/broken/missing, amazing how many used sets have the float mounting towers snapped off, must be a lot of ham fisted "mechanics" out there, snapping stuff off the carbs....

anyway, back to the Keihin FCR 39's, has anyone fitted a set to a Laverda triple......?

Paul LeClair
 
I thought Lothar runs FCR41 on one of his bikes and I think Tim's done several conversions, he's certainly been discussing it for 4 years ..
 
Speak to these chaps. ALLENS PERFORMANCE. i spoke to them a few weeks ago and for a set of 39's adapted for a laverda is about ?1100. Very helpfull and very knowledgeable about all things carbs.
 
These guys also have new at around US$750

http://www.nichecycle.com/Items.aspx?code=RSCARBRACK&key=cat
 
Hi Paul,

I have Keihins on my 1200 Jota (40mm) and on the SFC 1000 (39mm) and they can be made working very, very well! Points to consider:

-there are carbs with choke (OEM, used on new bikes from Suzuki and Yamaha from the early 90's/late 80's) and without (aftermarket). I would prefer the ones with choke and if you need, I have some choke-slider rods laser-cut out of 1,5mm stainless that I can sell you for 25? plus shipping (which is what they cost me).

-one accelerator pump is enough to make it work, everything more is just more fuel thrown in.

-make sure you get TWO fuel feeds, one between cylinder 1 and 2, the other between 2 and 3. Not only that it then only takes two fuel-lines, you also have a way better fuel-supply!

-make sure you use 2.8 float valves! OEM carbs mostly come with smaller ones due to fuel-pumps being used to feed the carbs. No fuel-pump => use 2.8. With fuel-pump => use 2.0

-most FCR come as downdraft carbs. due to the angle of the engine with a 36mm SFC head (which I have in both bikes), the DD will work, but side-draft would be better (float-level...). If you use the angled inlets from Red, SD is a MUST!!

-The right carb will touch the tank. You need to GENTLY work on that area without cracking the sucker (tank), which I did. Not good.

-Setting up the carbs is relatively easy, once you understand how they work (just like with the Dello's...  :D). There are only some parts you work on and the main things are main jet and needle/-position. I can give you a good starting point which will make the bike run well, but both bikes run on the rich side here, which is causing - if pushed hard - a consumption up to 10 Liters/100Km (Dell'Ortos if set right are about 7/100). Might be possible to lean out the setting, but any attempt I did resulted in a poor accelaration, so I leave it where it is. Maybe a sign of the carbs being to big?!?

-the right bellmouthes make a difference! I can provide you 3 in billet alloy for about 75? plus shipping; they are made like the original Keihins, just not in that ugly blue plastic but in slightly polished silver. Nice...  ;)

The 1000SFC pulls now from around 1700 to redline, the Jota from 1200 - Redline.
 
Hi Lothar

I am busy painting two complete sets of motorcycle bodywork at the moment, finding a set of Keihins and setting them up is next on my list of Laverda things to do, I'll contact you when I find a set of sidedrafts...

Thanks
Paul LeClair
 
Paul,
My Spondon has 41mm FCR downdrafts on it and I have a spare set of...hmmm, I'm thinking they are 38s waiting to go on. I think I have a file around here someplace listing the jetting on the 41s which should be pretty close to what 39s would need. I'll look around and see what I can find.
 
Paul,
This is the jetting currently in the 41mm FCR downdraft carburators on my Spondon framed bike. The motor has a ported head, high compression pistons, Axtell cams and a free flowing taper tubed header 3-1 exhaust system;

170 main fuel jet, 200 main air jet, 52 slow fuel jet, and ocelv needles on the top groove (lowered all the way, their leanest setting).

If I remember right the needles are not a Keihin part but I think are a taper supplied by Sudco, or maybe Motion Pro.

The bike ran quite well at sea level in California and I haven't felt enough of a change since moving to Colorado (around 5200ft) to bother rejetting.
 
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