Keihin fcr idle circuit I just bought a 04 YFZ that wouldn't idle and has a hot no start issue. As you have surmised, it appears you are getting too much fuel for the available air. I am going to list stock, as received, and the final jetting specs I ended up with. It seems you think that either the pilot fuel screw circuit, or the pilot circuit, is only activated after the slide is lifted slightly. 2006 Kawasaki KX250F. Sep 21, 2015 · Right at the end of this, is a discussion on idle jetting - BikeBoy. very easy to use ,once yu get the hang of it . Made in Japan. I explain an easier way in the video above. 25 in does not drop the idle, the pilot is too big. Turning the IDLE MIXTURE SCREW out will make idle and off-idle richer. 1000 ft above sea level These are the jets I have at the moment: PILOT AIR JET - 60. Turned fuel screw all the way in and bike still runs. link/tusk-carbureto Okay. But based on what some of these other guys are saying, it could very well be your needle. 00 Add to Cart * KAWASAKI KLX 400 400R Billet Keihin FCR-MX Dec 21, 2014 · With stock ignition and fcr's you have to go below 11 AFR at idle to completely avoid the hanging throttle. Fitted my FCR today at long last. The Pro Circuit Hot Start Connector is CNC-machined from aluminum and eliminates the danger of this important carburetor part from stripping. Supplied from Yoshimura, with one accelerator pump, set up for 91-95 ZX7`s (should fit right in, on a ZX9 -95 engine!!??) The IDLE MIXTURE SCREW (FCR) controls fuel delivery to the idle port and the SCREW is located on the engine side of the carburetor slide. Mar 26, 2012 · 1994 Ducati 900SS with Keihin FCR 41 Sudco kit. Page 208 8-44E Assembling the carburetor Keihin FCR-MX 41 – Mount the idle-air jet and the main air jet – Place the O-ring in the groove and secure the intake trumpet to the carburetor by means of the 2 screws. Adjust while hot 1/4 turn at a time. 5 turns out Dec 9, 2016 · With a few mods, the Keihin FCR carburetor found on many carbureted KTMs, Hondas and Yamahas can be tailored for better throttle response. Typical engine response is an idle and as the engine heats up, for the idle speed to increase. This is driving me nuts. The front of the slide has a plate in it that is held in by friction, with an o-ring. Newbie here to all this. 80 LJ. As far as the air/fuel screws, the air screw (on the front of the carb under the velocity stack) when turned IN richens the idle mix (less air thru this circuit). Washer All 0301-078-1200 021-101: Feb 15, 2019 · I'm sure I've seen this link in one of the pumper carb posts before (buried somewhere). Anything I can do besides buy a new pilot jet and/or carb rebuild kit? What else will affect the off-choke idle? Thanks for any advice, Nolan Oct 17, 2023 · It can be ridden, but only with the throttle plate cranked open a bit to force the idle high enough to not die at idle. This SCREW is May 22, 2014 · All, I apologize for starting a new thread on this topic, especially as a first post, however I absolutely cannot figure out the issue, and can't find any posts from after 2012 regarding removing the PAJ in the FCR, so I think that perhaps this (or something else on the carb) may have changed. Just adjust to where you have a smooth steady idle. It consists of key components such as the idle jet, air screw, and the passageways that regulate fuel and air mixture at idle speeds. Keihin carburetors [ USED ] 2-stroke 4-stroke › FCR single FCR MX FCR racing CR Special Keihin carburetors [ NEW ] 2-stroke › PE roundslide PWK / PWM / PJ 4-stroke › FCR singles › General Honda Suzuki FCR MX May 10, 2017 · If you own a modern 4 stroke dirt bike, then it is equipped with a Keihin FCR carburetor. 2. On FCR carbs the main jet, slow jet, jet needle, air adjustment, slow jet air adjustment and gas valve are different and located elsewhere. For FCR-MX carburetors wi. As usual, the correct diagnosis is half the battle! Note: All the vintage Hondas supported by Randakk’s have Keihin carbs with idle FUEL (not AIR) mixture screws for adjusting pilot circuits. Aug 31, 2011 · A Keihin FCr is one of the best mods that you can perform on a 650R. MAIN AIR JET - missing (ordered standard 200) MAIN JET - 165. 0 to 2. The carb is a Keihin FCR of some sort (pics below). 42 is the smallest I have tried. lots of differencesso i will condense the majority of the thread to info pertinent to my all time favorite 4-stroke carb the KEIHIN FCR carb. Out of gas; Incorrect starting procedure – when cold step on gas once, then crank. It runs awesome. 5 turns. If you end up at 2. A more complete description is found in my article, Keihin Idle Circuits White Paper. you get into the ecu file and take the ignition advance at closed throttle out from maybe 2,200 rpm down to a bit above idle. complete kits (224) keihin (13) keihin cr special (2) keihin fcr (87) keihin pe (5) Sep 15, 2016 · After you get the main right then you can play with needles and screws to make it take off good and idle and start good. Been through it a couple times, had to rejet and adjust to get it idling and running right, but still having some trouble. You may want to call sudco and see what they recommend. Circuits We Are Going To Jet. PWK General: PWK Carburetors Angle carb adjuster parts for 021-586 order both 007-757 and 00. Then attach and tighten the idle-adjustment screw and bracket. Kits include diaphragm, spring, “u-ring,” o-ring, and 4 x 8mm screws. Feb 23, 2023 · What’s the factory idle adjustment for a ‘21 TRX250? Mine has always taken like an absurd amount of time to warm up and idle without choke and last time I started adjusting the idle thinking it may be too low. seemed to be good before. If your needle plugs your main too much, might have similar effect. i think they changed the plug to the same as the 450 around 07. Depending on your type of riding adjust the minimum idle speed to desired rpm making sure the engine is up to operating temperature. Clip position 3 is ok. In slightly rich cases, the engine will respond well to throttle blips when cold, but will die or dip slightly below idle speed when hot. Nov 13, 2014 · On the dyno, Engine has excellent bottom and top end, however going from idle to wide open it wants to go way lean. Nov 12, 2022 · Proper FCR idle mixture diagram attached. -----Check out the Tusk Carburetor Mid-Body Gasket Kit: https://rmatvmc. All the 4 stroke dirt bikes are equipped with Keihin FCR carburetors, so this post should guide you in the right direction no matter what brand you own. Nov 8, 2012 · If you find yourself RAISING the idle screw as you tune the fuel screw out to drop instead of raise the idle, you are doing it backwards, and you will end up with a very rich pilot circuit. Replace with what jet? A 48?? Condition of the seal between the roller slide and the floating plate? I'm not sure where this is? Is the floating plate in correctly (not upside down) Also not sure what this is? So Ken, my all knowing friend. Feb 5, 2017 · KEIHIN FCR-MX 39 Setup Guide &amp; Jetting Tables Quick update. NEW GENUINE KEIHIN Angle carb adjuster parts for 021-586 order both 007-757 and 002-065. took me a couple of hours , [playing around to figure out best combo's for my bike. Aug 13, 2016 · Turn right to increase idle speed, turn left to decrease idle speed. Feb 1, 2014 · Need some advice on my jetting. 105 PAJ. Back to 42IJ with remote adjustment screw now in. Description, exploded views, testing & troubleshooting. never can get the pilot circuit to get lean enough even with a 35 jet 2 turn out. TEL: 951-738-8050 FAX: 951-738-8065 ADDRESS: 2771 Wardlow Rd. And yes, the mass of air coming in has an effect, as does the fact that you need to open up the throttle slide more to keep a good idle speed at altitude, thus changing the vacuum "signature" at the pilot My DR650 whose name is Kelly :rose: sports a Keihin FCR-MX39 Flatslide Carburettor upgrade. Jetting Specs. 5mm has leaned out the pilot circuit. Idle still hangs. Keihin FCR-MX37 Carb Keihin jets FCR-MX carb carburetors and parts . the accelerator pump now puts more fuel into the cylinders than it did before and the bike revs up great. PILOT JET - where is it?! Not next to main jet as in May 13, 2013 · 'Normal' choke operation (enricher) is to add fuel AND some air. There is always air flowing under the slide mixing with fuel and air that flows in the pilot circuit. Hanging Idle with FCR Gen2 carbs explained Many people have had a hanging idle or idle that is slow to come back down. February 24, 2009. Yes, as the slide raises fuel begins to flow thru the main jet from the needle jet. Basically because of poor design and woefull atomisation with smaller air correctors the Keihin FCR design will not Apr 23, 2012 · The dreaded hanging idle, or as i started calling it - "Cruise Control" I have a 2007 YZ250F, with std everything - apart from the aftermarket Pilot Air Screw which allows finger adjustments. But the carb isn't able to respond to that change in airflow instantaniously. Ari details the classic symptoms of this very vexing issue. keihin is a subsidiary of Honda Motor Corp and their 2-stroke and 4-stroke carbs are state Apr 13, 2017 · This post is about me installing a FCR Mx 39 carb on my 650R. What i'm saying is that the hanging throttle with ducati&fcr's is not actually caused by a lean condition as the common wisdom says, but can indeed be circumvented by tuning the idle mixture very rich. Normally, set them both at 1 turn out and adjust from there. AFR's around 18. Jul 10, 2007 · 07 Z400 Yellow HMF Sport Blue Slip On - CRD Header|YFZ 450 '05 FCR 39mm / Keihin carb|EHS Airbox Lid - Uni Filter|Hot Cams I & Ex - DRZe gaskets - DRZe valve springs - D. Apr 17, 2018 · I've decided to attempt the mid-body gasket replacement on my vintage 2000 slant FCR carb, stock on the DRZ 400 E. link/tusk-carburetor-mid-body-gasket-kitTusk Carburetor Rebuild Kit: https://rmatvmc. Tore into it today and I have a 55 slow/170 main. Feb 24, 2009 · The Keihin FCR Carb Rebuild With Zip-Ty Racing - Dr. Took the pilot screw 2 1/4 turns CCW from full CW and now it bogs worse from idle or dies. Aug 24, 2006 · The leak jet is part of the Accelerator Pump circuit. fixes it instantly. The oval shaped throttle valve concentrates air flow over the main fuel circuit to increase low-end response. You go smaller or larger on the pilot jet to achieve this Fixing the Dreaded Lean Bog on Keihin FCR Carburetors: I recently had the pleasure of performing a complete frame down rebuild on a 2007 CRF250R that came to me with an intolerable bog issue when the throttle was stabbed from idle or low RPM (both when riding, and on the stand). By karel kramer. A comprehensive diagram should highlight and explain the function of each of these parts, allowing enthusiasts and mechanics to gain a deeper understanding of the carburetor’s inner workings. I need your advice. Apr 27, 2022 · To adjust, the idle screw is turned in until the engine misses and then turned out until the engine ‘rolls. I really had no complaints about my 2008 KTM 450XCR-W test mule’s carburetion, at least not after jetting and adjusting it for local conditions in my home state of Tennessee. It can be annoying to deal with and it is not a jetting issue. The accelerator pump delivers extra fuel to the intake when the throttle is suddenly opened, compensating for lag in fuel delivery at quick throttle movements. I recently pulled my FCR carb off a 2008 CRF450r that was having trouble kicking over and a bog off idle. 35-39 FCR-D 018-866. Pilot circuit – This is effective from 0 to 1/8th throttle positions. that simple. Nov 24, 2013 · The bike will run OFF choke at the mid to high rpm range, but it won't idle off choke. 48 PJ. The Keihin VB carb's idle circuit is actually quite complicated. Clean or replace the 45 idle pilot fuel jet. there is also another jet (48). keihin is a subsidiary of Honda Motor Corp and their 2-stroke and 4-stroke carbs are state Jan 23, 2017 · I've been having issues on my 2008 KTM 450 SX-F w/ the Keihin 41mm FCR-MX carburetor -- I was having issues where I would be able to start it and have it idle, but then upon giving it a little bit of gas, the engine would stay with a hanging idle (1500 rpm normal to like 3200-3600 rpm depending on the condition). Start with the stock jetting and try The jets in a FCR-MX are the same as in every XR,CR,CRF Chech the XR650 and jetting fora on Thumpertalk. While having an exhaust gas analyzer is almost mandatory during tuning of main and needle circuits, do not rely totally on them to set idle mixture. It can come loose and cause hanging idle. Using the shank of a very small drill bit, adjust the idle speed screw until you can barely fit the base of the drill bit under one of the slides as you would a feeler gauge. Zero throttle operation - (idle circuit) idle screw: depending on your type of riding adjust the minimum idle speed to desired rpm making sure the engine is up to operating temperature The IDLE MIXTURE SCREW (FCR) controls fuel delivery to the idle port and the SCREW is located on the engine side of the carburetor slide. You should have the 39mm Keihin FCR carb Yes, you may want to also adjust the idle mixture screw if you can find it and reach it. Been reading up on getting my 80 xl250s carb ready for installation and came across this again. Dec 11, 2024 · FCR mid-body gasket. Jul 8, 2010 · Hello all, I am in the middle of rebuilding my Keihin FCR-MX 39, The original problem that led to a carb rebuild was my bike did not want to start very well or Idle after it was started. Feb 18, 2005 · Carb type: Keihin FCR 39, Flat slide, set up by Sparks Racing Main Jet: 170 main Pilot Jet: 50 Fuel Screw: 2 1/2 turns out Needle: Keihin, on 3rd clip from the top Bare Perfomance (aluminum) open airbox w/ K&N and Filtercharger Exhaust: LRD full ceramic Engine Displacement: 440 Wiseco w/ 13. New spark plug. When I first started the bike the idle was noticeably higher than before, so I'm guessing opening up the PAJ to 1. 5 turns to achieve max idle. TheKeihin FCR 41 MX carburetor also includes pilot jets, which ensure a consistent fuel-air mixture under idle conditions for smoother engine starts and better engine warm-up. Will idle with choke on, dies without choke. ’ The screw is then set halfway between these two positions. I. I reinstalled the carb, went 1 3/4 truns out on the fuel screw. At that RPM you are just coming off the idle circuit and coming onto the main jet. ie:dialed in Leak Jet or the Boyesen cover. Mar 8, 2012 · The nice thing about FCR's (and most Keihins) is that they have an accelerator circuit, which squirts gas down the throat of of the carb when the throttle is applied, with the engine on or off. 5 turns out. 5:1 piston, kit w/ new cylinder, Nikasil plating Hanging Idle with FCR Gen2 carbs explained Many people have had a hanging idle or idle that is slow to come back down. So yes, lean condition in the 1/10-1/8 throttle circuit, assuming I got the manifolds hooked up with no leaks. Should I seat it and go 2 out and adjust from there? Slant FCR vs FCR-MX Carburetor- Fuel Line Side: Keihin Older Version FCR 39mm Carb: Keihin FCR-MX Pump Linkage Honda 06 vs 07 CRF450R: PWK Carb Power Jet Tube Viewed from Motor Side: PWK Carb Power Jet Tube Closeup: PWK Carb Power Jet Tube Intake Side: PWK Carb Power Jet Location in Body on Right: Keihin PWK AG Short Body Carb: FCR MX Carb Max Aug 20, 2024 · Update: I wasn't 100% happy with the the pilot jet circuit and transitioning to the main jet circuit. 72 SJ. When i got there he was having trouble getting it to idle. The 50 pilot will help dramatically. Moreover, the carburetor features an automatic idle circuit to maintain a consistent idle speed regardless of RPM or engine load changes. gif: Yamaha YZ426 Needle Info. This provides for a rich fast idle. If you end up at 1 turn or less, decrease pilot jet size. When the carb's slide is suddenly raised, the engine takes a big gulp of air. R. I have an erm needle as recommended by sudco. 540 kit. 5 to 1 lap, but the idle remains the same, cold, or less than 70 degrees Celsius, less than 1,400 rpm, I can only try another The IDLE MIXTURE SCREW (FCR) controls fuel delivery to the idle port and the SCREW is located on the engine side of the carburetor slide. Mar 29, 2013 · Still dealing with the pilot circuit though. Mar 11, 2018 · Hi i’ve just bought a CRF150R 2008, and the bike wont idle. As such, you can find out a lot about the aircut system and what it does by reading my article. I installed the Keihin FCR41 kit from Sudco on my 1994 Ducati 900SS in 1995 and it was great, until I let it sit with fuel in it much too long (no excuse). All three bikes are from co Jan 2, 2008 · Idling into your driveway will always result in a rich condition as you are reading the idle circuit. air box with the rubber restriction removed. jpg: Power Bowl with Adjustable Pump: FCR Carb disassembly for clearing pump nozzle: FCR Carb disassembly for clearing pump nozzle: FCR Carb disassembly for clearing pump nozzle: FCR Carb disassembly for clearing pump nozzle: FCR Carb disassembled the #1 online shop since 2001 for genuine keihin carburetors made in japan. Some idle mixture screws are covered by tamper proof covers and set at the factory. May 9, 2020 · You should be able to set the idle speed to about 2000, then dial in the fuel screw back or forth and end up with a idle speed to about 2700-3000, then reset the idle speed with the knob and be done with it. ACV (for reduction of decel popping), full T venting for deep water crossings), Hot start circuit, Pivoting fuel inlet, Leak jet, TPS, Remote cable idle speed adjuster, etc. The general opinion is it is a jetting issue with the idle circuit. Use sparingly. A few tips: - pull the carb off the bike (mandatory) Mar 10, 2013 · there are lots and lots of carburetors out there. The "bog" that you get when whacking the throttle open from idle or low RPMs is (almost always) a temporary lean condition. (this is why the engine still idles sometimes when the fuel screw is fully closed. 7) as far as the taper on the needle look at 1/4 throttle and 3/4 throttle try to get them the same if there On FCR carbs the main jet, slow jet, jet needle, air adjustment, slow jet air adjustment and gas valve are different and located elsewhere. 20 hrs or under. If you are like me you have scoured the forums for info on doing this service but found maybe 2 or 3 pictures of a taken apart FCR, dead end threads, and tons of negativity. Share Ok thanks noble, I will put the original starter jet in and check out the pilot Keihin PWK PJ Single Taper Needles: FCR Needles list. This was an issue that was Feb 25, 2008 · The IDLE MIXTURE SCREW (FCR) controls fuel delivery to the idle port and the SCREW is located on the engine side of the carburetor slide. To eliminate popping on decel. If you need to go past 2 turns to get the highest idle, you need the next largest pilot jet. any thing higher makes it worse. It's from a Yamaha YFZ450 modified by mx_rob (cheers man!), installed and set up by me with the help of knowledgeable friends (thanks Thommo and Wallacey, also props to Jimmy and Richie at the Kustom Kommune if you're reading this). some fcr owners have a lot of trouble getting them to start cold, esp if you replace the pilot jets with a smaller size that doesn't make the idle crazy rich. currently set at 1. I'm guessing the pilot jet has some invisible issue from sitting so long, but I cleaned it so well Im really skeptical. (And I mean that in the nicest way). Once warm it runs great but takes way too long after cold starts. Apr 1, 2014 · there are lots and lots of carburetors out there. Runs great if you baby it threw til around 4800 rpm. Jul 23, 2015 · Check the slide play between the slide and the lifting bail arm that bolts to the throttle cam shaft. Jun 21, 2009 · Hi. Dirt - Dirt Rider Magazine. Anyway i went on it but he said i had to keep on revving it in order for it to stay alive. smaller pilot jets don't seam to make a diffence. I have done the NVCS needle, 165/170 main, 45/48 pilot, long pilot screw adjusted by 3 nubile virgins, used fresh fuel, tightened all boots, good plug, valves not run enough to be out, waved a dead chicken over the length of the bike under a gibbous moon, etc. Most service manuals and even aftermarket companies have really complicated procedures for setting up the pump shot timing. So, when it's cold out, twist the throttle 1-2 times, and crank her over. Throttle response etc is perfect. Zero throttle operation - (idle circuit) idle screw. The narrow design allows minimum interruption in the Jan 10, 2015 · Bike is a 08 Beta 450rs with T. I start the bike up let it warm up good and then twist the throttle quick and the engine falls on its face and then revs up or it just dies. – Insert the fuel port in the carburetor and fix with screw NOTE: In the mounted state, the connection piece must be easy to turn. Posting a link to mid-body rebuild (), but if it doesn't work because of my post count then just go to youtube and look up Rocky Mountain ATV's video on "Tusk Mid Body Keihin FCR Carburetor Rebuild Kit". The SCREW is located on the air keihin fcr service & ultrasonic cleaning (9) show all * services. As I open throttle from idle (choke off) the engine dies or flat spot and then accelerates if I just wait before engine returns to idle Regarding value, IMHO there is a BIG difference between the earliest (late 60s through early 70s) sandcast cr ticklers with no idle circuit and the replacement diecast version with an idle circuit that looked just like them(at a glance anyway) offered in much larger volumes. Jun 3, 2017 · This happens when the idle is set to normal, if I increase the RPM to around 1800 the bike will not stall with the mixture screw all the way in. By upgrading to a Keihin FCR carburetor, riders can expect improved throttle response, increased power, and smoother acceleration. d. The Keihin FCR MX carburetor is a good performing carb when properly tuned, but old age and bad gas or harsh carb cleaner chemicals can wreak havoc when trying to troubleshoot a “jetting” problem on a 4 stroke MX dirt bike. With its superior performance and tunability, it offers significant benefits for riders and mechanics alike. View it here. We just need a little more and earlier so there's never any bog out of the carb, even when opened fast and aggressively as is required sometimes to loft the front wheel predictably. <br />Ohlins rear, early 90`s SS Showa f adj fork w Ohlins springs, Toby st damper, Nichols Engine Bolts, rear raised 14mm, forks 23mm over triple, Sato f adj Feb 16, 2017 · The best part of this short video is the concise DIAGNOSIS of idle jet problems. Jan 19, 2011 · Second thought I find usually the idle circuit needs more cleaning, they have the smallest passages & get gummed up with ethanol fuel. Feb 23, 2014 · Also, sometimes it will return to idle quickly, while sometimes it will return to idle slowly but without the fluttering above idle. The carburetors also come equipped with a fine-adjustable idle circuit, enabling riders to fine-tune the engine's idle speed and stability. Jun 11, 2011 · To conclude, I want to tell you that I tried to upload a needle point (from 5 to 6) with the gum 48 and then to the bike goes well, (the stable idle at 1,500 rpm and engine braking) I had to adjust the mixture screw, 2. Apr 17, 2014 · Keihin FCR41s with stock Sudco settings, 94 900SS, I am experiencing what appears to be a fairly common issue, idle that hangs about 1200 RPM too high before settling to the correct level. The bike does start to die when I l Sep 26, 2018 · I have a lot of experience tuning Keihin CRs and they are sensitive to needle taper. Almost every FCR MX/CR 39-41mm carb on the planet is running a 42, 45, or 48 pilot jet, when jetted correctly. But in doing so the idle is something like 2000rpm and the carburetor is actually feeding the mixture through a different jet circuit -not a true idle through the idle jet circuit as is intended. N Aug 13, 2016 · as far as which idle jet to use , if you want the carb idle circuit (or slow circuit) to run in a tunable range then use the 45. A DRZ will not idle at 500 rpm. they probably taper the advance down from 25 degrees at 2,500 to 10 or so at idle (1,200 ish). Curious how long others take to warm up and idle without the choke on. i dont know if all years are the same. 5 turns does not drop the idle, pilot is too small. If turning the fuel screw past 2. Apr 14, 2014 · 2003 DRZ 400 E according spec in manual is a KEIHIN FCR 39 Single. 3/4 Cam Chain - KibbleWhite Valves|Dyna FS non-programmable CDI|Elka Long travel Rear Shock Triple Rate|Houser +1 swing arm|Houser carrier and linkage|DuraBlue +2 axle|AC Blackline Pro Peg Nerfs - AC Front Bumper |RAZR2's Im having trouble with an FCR carb. The idle circuit in a Keihin carburetor controls the engine’s performance at low throttle positions, ensuring a stable idle and smooth transitions from idle to acceleration. D. These include the fuel passage, the air passage ("bleed") that mixes air into the fuel passage, the discharge outlet inside the carburetor bore, the pilot screw cavity, and the three "bypass" ports immediately under the throttle plate. You might be able to do this in the outskirts of a mall parking lot. The Keihin FCR carburetor FAQ. It will run at about 2500 rpm for about 5 to 10 seconds before going back to idle speed. Home FAQs/ tuning Customer service Idle Speed Screw All 1034-815-4500 021-745: 91. Ba Feb 5, 2017 · Keihin FCR 525XC IAJ - 100 MJ - 178 NJ - OBEKR NJC - 4 (Adj to 3) CSJ - 85 IJ - 42 Slow/idle Circuit still a little blocked? Sent from my iPhone using Tapatalk . Starts and idles well. Turn the fuel screw once motor is hot, out, to raise idle. A couple nights ago I decided to commit and do the install of a Keihin FCR Mx 39 from a 2008 KTM 450xc-w on my 650R. May 20, 2020 · Adjusting the idle stopper or mixture screw I can get it better but not perfect, can't seem to find a happy medium, have tried 45 pilot (std) and 48 as well. However, I have a pilot jet of 42 fitted, not 45 as recommended as the dealer did not send me the correct one (I got ever Jul 23, 2023 · Here are the concepts involved with checking your accelerator pump. Without touching the fuel or air screws, I took it for a test and now it's perfect! Oct 6, 2014 · Year, Make, Model. you will want it around 12 at idle to make it start better then lean at cruse (1/8 throttle no load can be 14 to 14. The pilot jet is totally open. I already had the carb so I set it up like I have several FCRs in the past on other bikes. I have done bothit will NOT die with a quick closed to WOT pull. Feb 4, 2018 · It's worth the effort as the shops most likely only replace a $7 jet and get your bike running ok and then give it back to you. I have 3 bikes in my garage right now 1 a Honda CRF250X and 2 YZ250F's all with the same simptom. and ran the bike at idle. It felt like it was still a bit too rich,so I installed a pair of 45's as I mentioned I'd like to try in the paragraph above. keihin fcr / fcr-mx / cr special / pwk / pwk-s / pj / pwm / pe ultrasonic carburetor cleaning & rebuild service oem carburetor parts / gasket kits custom keihin fcr sets for engines not listed custom made keihin fcr shafts Keihin carburetor manual. Do you think that FCR`s are hard to tune? I am buying a set of 39mm Keihin FCR`s, got them for 500 dollars new in box. 5 turns (won't idle or stay running). I can get jetting adjusted right. Jun 5, 2006 · 900SS heads w polished ports & matched inlets, Keihin FCR 41 w KN pods, JE HC pistons, opened exhaust xover, SilMoto highmount ss, lw flywheel, alu clutchbasket & plates, DynaCoils, Ignitech TCI-P4 programmable ignition, 15/41 gearing. If there is no performance issue with the #50 And you like the sound better then go for it . Apr 5, 2019 · A carburetor at idle does not flow all the air thru the pilot air circuit. 3. Tightening down the fuel screw doesn’t fix it. You should try it John. A must have when working on the Honda Keihin fuel system. I've seen it on (5) FCR carbs now. I read if you cant fix the pilot circuit then try to change the throttle valve Created Date: 10/31/2005 4:50:48 PM Dec 31, 2001 · perfect jetting got my copy of jd jetting and i have to say it does what it says. By Chabochi, April 11, 2015 in DRZ400/E/S/SM. It was fine didn’t fully open it up so couldn’t identify any other isues but i did give Bought a used DRZ recently with a yoshi exhaust, 3x3 and an FCR 39 MX and cannot get it to run reliably - it’ll only stay running at idle with the hot start pulled. Also developed a knocking afterwards I Jan 5, 2021 · So I bypassed that circuit by giving the plunger a wrap of Teflon tape to seal the hot start circuit, and reinstalled. The engine should now idle smoothly. Oct 14, 2003 · YFZ450 GYTR +1 a-arms, Elka Triple Rates, TCS rear rebuild, AC Bumpers, Yosh pipe,Jet kit,K&N Pro design,Cam mod, Lonestar axle,hub/nut, x-factor propegs,Billet shifter,LED Billet taillight, HiPer wheels, Irazr's, Billet Gas Cap, Tag T2 Bars, Lonestar +2/+1Stem, Stainless Lines, Black/red Just added: houser swinger, WR450 crank kit and -4 TT flywheel! Jul 16, 2020 · Update many months later. 27. I have a FCR on my 650L with Dotcom from ThumperTalks jetting. Bad fuel pump – Remove fuel line from carburetor, place the open end into a jar or bucket and crank the engine. For what it's worth, the idle speed should be in that 1600-1800 rpm window. Aug 24, 2013 · stock Keihin FCR 39 (not MX) drz400e stock pipe with the baffle still in the muffler. It seems to run almost perfectly - the only issue is it stalls at tickover at traffic lights sometimes. After being on the throttle, it wont idle back down after letting out of it. . Dec 12, 2021 · I have a 2007 YZ450f. Bone stock. Stock: Leak Jet: 60 Aug 9, 2013 · If the idle speed screw is turned all the way in, it is not idling on the idle circuit. Mar 3, 2017 · Since I have the same or similar hanging idle issue on my 2006 DRZ-E FCR Carb, I searched this forum for "Hanging idle" and found a lot of information. carburetors. How to adjust the accelerator pump on a Kehin FCR Carburetor. but it's not your mechanics fault for your not knowing it, and not mine. mrs said there was a slight hang on it still when blipped at low rpm, will try a few tweaks on the mixture screw next time. For FCR Genuine “KEIHIN” replacement parts. Sep 4, 2014 · Start with the lowest possible idle adjustment when at 1 turn out on the fuel screw. They replace the 99101-ZF5 (old 99101-124) slow air jet and allow you to fine tune to an infinite numbers of positions without replacing any jets! Jun 7, 2024 · the tdmr have a choke. When high performance 4 strokes came on the market there was a flood of new products & ha Jan 12, 2025 · The FCR carb is a slightly different beast. PHOTOS BY MARK BARNES. Happy around 1500 to 1900 RPM. , and the idle is very erratic and Oct 22, 2009 · If you jet fcr's for cold at start/idle (they have no starter circuit) you will ruin it for 0 - 1/8th at operating temp. it would only run with the cold start on or the throttle opened off idle. Turning IDLE MIXTURE SCREW (CR, PWK, PJ, PE) controls the amount of air to the IDLE and SLOW CIRCUIT. If I'm reading this right, the idle drop procedure recommended by Honda is not the best way to go about things. The aircut system is actually integral to the idle circuit, the most complex circuit in any 70s-80s Keihin carburetor. It took a lot of kicks to start, and finally got it to start with some throttle. , Corona, CA 92882 Jul 24, 2007 · Dual Keihin FCR carbs on rails, prejetted to your application K & N air filter Twistgrip (throttle) Throttle cables Adapters for your intake manifolds Adapters for your stock airbox Velocity stacks Instructions I have prepared a supplement to Sudco's installation instructions. I cleaned the varnish with carb cleaner and that destroyed the various Jul 30, 2012 · Try a 50. NFLR Needle with clip in 3rd Grove from the top. The 42 made no real difference, except the bike was harder to start. 45 is the most common. Try raising the needles, if that does not work get ones with less of a taper. Oct 4, 2019 · guzzi breva series motors will hold up the idle when closing the throttle at say a set of lights. Attached Idle Speed Screw bracket Enclosure (for throttle cable) Different OPTIONS (specify when order)-FCR-MX 37 none -FCR-MX 37 air cut valve, hot start -FCR-MX 37 air cut valve, hot start, TPS-FCR-MX 39 none -FCR-MX 39 air cut valve, hot start-FCR-MX 39 air cut valve, hot start, TPS -FCR-MX 41 none -FCR-MX 41 air cut valve, hot start For GEN-3 KEIHIN FCR-MX carburetors 37mm - 44mm with Non-Removable adapter. JD Jetting has a nice idle screw with a knurled knob. if you use a baseline that is to rich to begin with then the program will Additionally, the Keihin CVK32 carburetor features an idle jet, a choke valve, and various other parts that are crucial for its proper functioning. I can go idle to WFO and my bikes just rev up. Keihin Flat CR Horizontal 41 FCR-H 018-871. After the head was rebu… The Keihin VB carb's idle circuit is actually quite complicated. html, Keihin FCR Carb Tuning Procedures Aug 10, 2021 · Engine Cranks but Won’t Start. the first year or two of the crf 250 carbs were 37 or 38 mm, they can be bored to 43mm but you will end up with a combo taper in and stright out bore job. The early sandcast ones have sold in the multi thousands. Jetting is as follows: 175 MJ. Your goal, according to Keihin, is to have the fuel screw at 1. The FCR and FCR-MX slow air jet conversion kits fit all Keihin FCR and FCR-MX aftermarket carburetors. Apr 11, 2015 · Keihin FCR 39 wont idle. Although will not take throttle input with choke on until you get to the main jet circuit. runs find from sea level to about 2500ft but runs real bad after 2500ft and higher just off idle to 1/8 throttle. It's yours. Choose a place where you can coast off the road and have a safe area to pull the plug. The FCR-MX carbs are advanced technology carbs which have many different tune-able items and once that are properly dialed in are usually better than EFI setups on bikes. org - Ducati 900SS Carb model with Keihin FCR 39 and 41mm carbs And this is a good tuning guide - carbkie. to fix Oct 13, 2011 · the only fcr the i know that plugs right in (tps plug that is ) is the crf 250. The problem lies in the bikes 3d ignition mapping! In plain english your bike's CDI works on a 3D mapping. the most important part of the program is getting a good jetting combo to use as a baseline to compare to. Jun 13, 2014 · On FCR carbs, the fuel screw should be between 1. Turning the IDLE MIXTURE SCREW out will male idle and off-idle richer. Dec 29, 2008 · This is a 2002 400 EXC (Keihin FCR 39mm carburetor) I just finished cleaning & rebuilding the whole thing Before the rebuild, it would ONLY run with the choke ON Jan 17, 2011 · Very helpful. The bike has a factory exhaust and as far as I can tell the airbox is standard but the snorkel has been removed (in pictures) The jet sizes are 45, 65 and 142. Is it running on all 4 at idle? Long shot: since these are probably a set of used carbs, someone may have reeaally leaned on the pilot screws and messed up the seat/port at some point. BOTH circuits work simultaneously with the slide closed. Oct 13, 2014 · The Keihin FCR's are beautiful carbs, and I'm sure they'll outperform anything else on the planet, but it seems to me putting these $1400 carbs on a 70's pushrod, air-cooled, british twin that makes maybe 60-65 HP (in good tune) is a little over-the-top (not that there's anything wrong with that). Can't stop grit from grinding stuff away. 5 or more, increase pilot jet size. The dirt bike featured in this blog post and How-To video is a 2006 Yamaha YZ250F. Dec 31, 2019 · It looks to have all of the options available on a FCR other than the on-carb hot start plunger. The one and only issue with the FCR remains the timing and strength of the accelerator pump squirt. Crap in the idle circuits, still? Yeah, know you said they're clean, but just swapping carbs and it idles fine pretty much isolates the problem to the idle circuit. It has several openings. If turning the fuel screw past 1. Service manual doesn't list a specification for how high the slide should be at idle, only idle speed of 1800rpm and mixture screw setting of 1. If it goes too high, drop it withe the idle screw, and keep turning the fuel screw out. Idle mixture is just a tick rich but happy where it is 5000-8000 rpm wot AFR is perfect. If the idle circuit is not properly Oct 10, 2009 · Getting closer Starter jet fuel line will be Tee tapped into the existing fuel line with the toggle switch wired into the fuel pump timer to trigger the automotive 12 volt electric gasoline fuel shut off valve , Mar 6, 2013 · Base on this my guess is your idle circuit is too lean. Kits available for Keihin Downdraft & Horizontal carbs and Keihin FCR-MX carb. Had a hesitation/bog off idle and never seemed like it was performing at potential. FCR Accelerator Pump Rebuild Kits for Keihin FCR Carburetors. The Goal: Perfect Timing Aug 5, 2012 · - With the 38 pilot still installed, I attempt to tune the pilot circuit by finding the highest idle with the fuel screw adjustment - Highest idle occurs with the fuel screw all the way closedidle gets lower and lower with each half turn outthis is with a 38 pilot - Install 35 pilot jet and put the A/F screw at 1. I have an older style FCR bored to 43mm on my XR680. but until then it just isn't getting enough fuel. I fixed this problem before by remov Sep 12, 2019 · Hanging idle with carbs can be 4 things, 1) a mechanical issue not allowing the slides to close quickly 2) an issue in the enrichener, leaking or not closing 3) a lean condition caused by either a leak in the intake tract between carbs and engine OR a lean condition caused by a clogged pilot circuit within the carb. Now if you didn't know that stuff, sorry. Sep 2, 2008 · It is #7 in the Accelerator Pump Circuit diagram. The Keihin FCR carburetor is a highly sought after upgrade for motorcycles and other vehicles. Glue the plate back in place with 3M weatherstrip adhesive. Drained gas, added 93 and sea foam, took off bowl today and cleaned jets etc. i've been trying to think of a way to either physically choke an fcr within the std airbox, or an add on enrichment circuit. The small wheels, and even the slide lifting track, can wear (normal for a machine with poor filter maintenance). The air screw controls the amount of air entering the idle circuit, while the fuel screw adjusts the fuel flow, providing more or less richness for the idle and low-speed circuits. Mar 31, 2012 · The idle circuit settings should all be good. $65. com for more jetting specs/advise. Apr 12, 2005 · With the FCR fixed right. The FCR-38 set is constructed from high-quality materials, including a lightweight yet robust aluminum body and brass components for durability. Changes from normal (1,800 rpm) to as high as 3,000 rpm is normal. Didn't mess with fuel screw yet. Bought a 08 yfz450 and it won't idle without choke on. elevation ca. Jan 10, 2022 · A friend who literally wrote the book on tuning Keihin FCR flat-slide carbs had a good technical explanation in the document he wrote up. wearyhwo ngwnnb rgpfztt kwdh jhzh jjj tmg bfycg xwuvxp wqhzj