Hi all, I took the bike for a run today, and it seemed that it was running a bit rich. Anyway, the ride was fine, but it was sluggish and getting back it kept cutting out on the drive. I noticed there was a lot of fuel leakage from the overflow pipes as there was a fuel patch on the floor. Getting her indoors I could hear a gurgling, like a drain misbehaving, so I opened the tank filler and disconnected the breather, but I could still hear it. I then realised it was coming from under the tank, so lifting the tank and taking the filter off I could see that the inlet of the right hand slide going to the front cylinder was filled with fuel which was gurgling away merrily to itself. - which may explain explain why my tank seems to mysteriously empty itself over time! I closed the fuel tap under the tank, and opened the throttle so it'd pour into the bore. I noticed there was seeping from around the inlet manifold rubber. Has anybody had this or perhaps shed some light on what's occuring? and if so what to do to rectify it? 41mm Keihin flatslides. Thanks in advance people. :/
Yes fin yes, last week, 4 months ago, 7 months ago and so on. Fuel screw opened to much, it moves on its own in case of my bike!!!!!
Thanks Lucozade. Where is the screw?, can I get to it without taking the carbs off or is it a surgery job?
What angle are the float bowls sitting at, is it the front or rear cylinder, and have you got both carbs as downdraft or the rear as a sidedraft? Lucozade: exactly which screw do you have an issue with?
What i am trying to acertain is the angle of the front carb, there are some manifolds that are sold on the internet that set the front carb at a funny angle, ie, too steep. it could of course be a bit of rubber fuel pipe stuck under the float needle/seat.
They're Keihin FCR 41 flat slides. as for angles I'll have to go and measure. Its the front cylinder. As far as configuration, it's whatever was supplied so they're not split FCR's - I believe they might both be in downdraft as both front and back ar bolted together in the sameorientation. http://ca-cycleworks.com/products/fuel-carbs/016-721
What Sev said. I had issues with that from day one, I even had entire tank empty to engine. Went on holiday, came back 2 weeks later tank dry all in engine mixed with oil. Crap. They are linked FCR's like on photos below. Float bowls I would say are at 45 degrees, probably less. I have to turn the fuel screw all the way in and then back to my setting every 2-3k miles. F-ing annoying. Still when I was red-lining it for few days I had to do reset anyhow as it started pissing. Sev depending where your oil cooler is mounted you might need to unscrew it (no need to disconnect). Check what position (how many quarter rotations) your fuel screw is out on good side and repeat on the other to see difference. Ten reset it all. It is a down on the floor, good screw-driver job. Do not make mistake I did good screw-driver or you will kill your brass fuel screws. I need to replace mine as they are knackered. Will replace them with remote adjuster from M&P but carbs require little mod to get them through. Default FCR settings for Ducati here: Keihin FCR FAQ Description of all screws (and position) here. Inside the FCRs
I only had two problems with the fcr setup both on different bikes, one was dirt (looked like rubber bits) in the needle seat, the other was the front carb angle on split singles causing wrong fuel level, both pissed fuel out but still ran. As for the screws backing out, if there is wear on the o ring round the screw that can be a cause of that problem, after that i do not know.
I knew there was a good reason to stay with the cheapo OEM BDST Mikunis and try and get them sorted...........Buggered if I would fork out £500 to p*ss petrol straight down into the cylinder with all the damage that can cause.... .....but I wouldn't mind trying some pumper Dellortos on some altered manifolds.... AL
Well AL I kind off agree here sadly did not know it then. It seems most have trouble free fcr usage but there is few. Also solution for this is quite easy, £25 gbp on top for remote fuel screw adjusters. Right down the settings when all is sorted and just every couple of k reset it.
I learned my lesson poncing about changing carbs.........years ago I built a 1275 Cooper S engine with a crossflow head and four Amal concentric carbs facing forward........what a sod to set up that was.......... .........and then on one of our Kawasaki outfits we junked the four OEM Mikunis for carbs that were supposed to be much better............well they might have been, but I never saw the improvement..........nothing but trouble and we reverted to the OEM ones. AL
Well they are better then stock carbs, pickup is better, idle is better, crab icing is controllable but as many good things they have well there is as many bad.
My FCRs have so far been trouble free. MPG is good, smooth running etc. etc. I think that they may be a tad lean right now, but Im going to change a few things soon, and I will take it to a rolling road to set up the air fuel ratio when I'm done. That should be the end of fiddling for a while, as any more engine improvements are going to be disproportionately expensive. Some people have reported that FCRs flood because of the constant head design, where the fuel pump in the tank delivers fuel to the carbs, then returns what is unused to the top of the tank, so the fuel pressure at the float bowls should remain constant. However, when you install FCRs, this constant head might be a little too much for the floats to cope with, and you get fuel coming out from the overflows. Fortunately Ive not had this. Possibly the solution is to pay very close attention to the float valves, and float heights, and make sure that they seat properly, when you put the carbs together. I would probably want to rig them up on the bench with a head of fuel slightly greater than you would get from my ss, and see where the fuel level in the floats is, and wether the float needles are doing their stuff. Set that first, and then play with needles pilot screws and jets afterwards. We should use the experience of others and learn from it.
rough women after they've been out in the cold for too long. Lucozade, where did you buy your adjusters from is that per carb or for the pair? 25 quids well spent I think!
An FCR newbie here but I've plumbed mine with an electric fuel pump that pumps a loop back to the fuel tank but with a 'T' off to the carbs. The thinking being that any overpressure simply returns to the tank with the carbs getting a plentiful supply but not 'forced'. Also, as the return in the tank is low (i.e. tank) and could gravity feed I have fitted a one-way valve on the return line so that when the bike is standing there can be no pressure on the carbs, only the fuel in them and the feed pipe. I have also got an electric fuel shut-off valve that I was planning to fit but not round to yet, although if the one-way valve doesn't misbehave then I won't be needing to.
Lots of comments here i agree with particularly the one from luca. Chewy does hit the nail on the head with the bench testing and getting the pressure right. the two problems i encountered were when the job was rushed and time was short, if you are methodical there should not be a problem. These ARE a great carb for these bikes and are well worth the time involved in rolling road setup and getting right, fuel consumption is overall better on a run BUT that will change as the amount of fun increases. I did finally go for an electric pump from a carb yam r1 and have had no probs since, i still feel getting the float bowls as close to level will help any installation, and incedentally that is when the big drain bung on the bottom is as horizontal as possible i used these on a run across europe and got around 65 mpg cruising at 65-85mph on a monster however the arse soon fell out of that when it got to the twisties in italy. And as for crab icing, thats what you get with 10 hours in the saddle. Happy carb fiddling.
On monster I have pressure fuel pump not electric and no return to tank. I guess if I had return I would never notice those problems hence many on SS do not notice it. There is no way carbs would dump fuel to engine with electric fuel pump as when ignition is off petrol will not go through pump on gravity alone. With vacuum one and tank being over the carbs it will push petrol through even at stand still if it feels like it. Sev, These are an option but never used: R&D Keihin FCR Flex Jet Remote Fuel Adjustment Screw | eBay These are what I got but they are slightly to wide to go through screw-driver opening so you will need to mod it. As in take a drill and make the hole slightly bigger about 1mm should do. If you open the bottom cover to expose fuel screw you will see there is plenty of meat there to do that before you are anywhere near the seal. Tip do not loose the tiny spring that is on the original fuel screws you will need it New Carb Alloy Fuel Screw Mixture Adjuster for Keihin FCR Carburettors | eBay
