Good riddance to FCR carburetor

[exaresix]

I finally gave it up! I tried the FCR 41 carb on my xr600r, supposedly the hot set-up. This was not the FCR MX 41, but the standard FCR that Sudco recommends and sells as a kit with cables and bell-housing specifically for the xr600r. Although Sudco maintains that they have jetted it perfectly (50 pilot, 170 main) for the xr600r (with snorkel removed and a medium flow muffler), they are way off. Even with the mixture screw turned all the way in, and using the smallest jet in the "kit" (a 48) it still is too rich to pass emissions testing. The 170 main ran way rich on the dyno/EG analyzer. The carb has no choke, so it's a PITA to start cold, and it is also very difficult to start hot. If you get the bike running, don't stall! The mid-range throttle response was great, and it was hard to give that up, but in the real world, you have to be able to start your bike, and in many areas (e.g. Phoenix), you have to pass emissions. I've now heard that you have to go down to a 42 pilot jet. Who knows where the main should be. The dyno tester in my area told me a 143! I tried that, and the bike was down on power.

If I'd known better I would have bought the MX version that has a choke and a hot start button, but Sudco didn't offer it in kit form for the xr600r, nor did they recommend it. The MX carb alone is $560 and comes equipped with several clear pink vent hoses that some have likened to an octopus on top of the carb. I also notice that Xrs Only has pulled the FCR carb and the kit from their on line sales. I'll bet they had a lot of complaints. When Sudco calls this a racing carburetor, that's what they mean — this $525 non-refundable unit is not suited for the real world. I'm back to the stock carb.

[MartinDKtm]

No choke no problem...twist the throttle a few time 3-5 in the morning and the accelerator pump will do its job and it does start right up. I have the edelbrock on my 650L and start like a charm without choke even a 0° Celcius. People here will give you a good jetting setup for it im quite sure.

[exaresix]

Yes, I've heard the pumping routine, but even Eddie Sisneros agrees that no choke is indeed a problem. If you have electric start, ok, maybe not a big deal, you can crack the throttle a tad as your little starter churns away. For a kick start, it is a problem for me. As far as jetting suggestions go here, I have heard everything from a main of 143 to 190, and none confirmed with EG analysis. This is a massive range of suggestions. My carb bogged at WOT with anything over a 150. Pilot jetting is a little easier to work out, but after failing emissions four times in a row using the recommended jets, I was done, especially having to flog the kick start endlessly for the hot start. If I ever get a pumper again it will probably be the pink octopus (FCR MX), but that's another $560 I need to mentally wrestle with.

[Beyond The Pale]

You are really comparing apples to oranges. The XR600 is an off road bike. The Sudco kit was never meant to pass any type of emissions testing. Sudco sold it to provide maximum preformance. With any carb you are going to be down on power to pass the emissions test. Jet it to pass, then jet it to work right.

Since the XR600 was never designed or tested for on road emissions, how does Arizona decide what levels to test for? Do you have the HC, CO and NOx numbers that they are looking for?

As far as I know it is not "many areas." The only area on earth doing smog testing on bikes is the Phoenix metro area. At least for once California is not in the "lead" here.

For what it is worth any larger carb is unlikely to pass. They just don't work as well at low throttle settings from an emissions perspective.

I have the stock carb and I had to remove the choke plate due to metal fatigue. I have started it down to 25F with a special simple procedure. Turn the gas on and lean the bike over. Normally this causes flooding. Here it is priming. It will usually start on the first or second kick even below freezing.

[exaresix]

In Arizona carbon monoxide levels (a measure of how rich the bike is running) need to be less than 5.0 — simple as that. xr600s have no problems passing with the stock carb and recommended jetting. The CO levels with the recommended pilot jet in the FCR are 10.0 with the mixture screw turned in all the way. I have a few bikes with big carbs, and they all pass emissions with the recommended idle jetting. They test for HCs too, but this is rarely an issue.

As far as Phoenix metro area being the only place where emissions are tested, this is false. The entire Maricopa County (where Phoenix is) has to be tested. This county is over 9000 square miles — larger than many states. Phoenix itself is the fifth largest city in the US and has many many off-roaders, so were not talking a trivial number of people.

[martinfan30]

man im sorry to hear your troubles! that is strange, i wonder why it works so well on my 650l and your 600. but sounds like you are done.?

[exaresix]

martinfan30,

Do you have the FCR MX or the standard FCR with no choke or hot start button?

[Beyond The Pale]

Well that is not a very tight test, but getting from 10 down to 5 would be pertty tough if you already have the smallest jet and the screw closed.

There are a few tricks that can help. One is making you own oxygenated fuel. Get a gallon of alcohol from Home depot and make a little emissions mix. You can run as much as 30% alcohol. This leans out the mixture and reduces CO (and HC at the cost of more NOx).

I've never had my bike on an emissions testing machine, but I'm sure that the CO would be at least 5. With the stock non pumper carb, the pilot needs to be rich for decent throttle response.

[exaresix]

I quite agree that it is nice to have a slightly rich idle, but you can do that in most cases by adjusting the idle mixture screw...and yes, I could have finally gone down to a size 142 jet, but it's history now. My stock carb is running ever so sweet, and I know it'll pass emissions, I can use the choke for cold starts, and I can start the bike when it's hot. If it gives me trouble in the field, I know how to disassemble and check every part. I also know that my plug is not building up carbon due to chronic rich conditions. It's a simple carb I can depend on, no air jets, no pump duration, no abnormal cable routing, nobody at the distributor (Sudco) telling me the jets they put in are the right ones and should pass any emission (even though the pilot is so rich that the mixture screw does nothing)...just plain stock OEM boring carburetion! When I'm feeling another $560 flush, maybe I'll buy an MX, and I can take it through emissions another four times, saturate my hands with gasoline, and throw it away after everyone says: "What did you expect? This is a racing carb!":ride:

[mgs781]

I quite agree that it is nice to have a slightly rich idle, but you can do that in most cases by adjusting the idle mixture screw...and yes, I could have finally gone down to a size 142 jet, but it's history now. My stock carb is running ever so sweet, and I know it'll pass emissions, I can use the choke for cold starts, and I can start the bike when it's hot. If it gives me trouble in the field, I know how to disassemble and check every part. I also know that my plug is not building up carbon due to chronic rich conditions. It's a simple carb I can depend on, no air jets, no pump duration, no abnormal cable routing, nobody at the distributor (Sudco) telling me the jets they put in are the right ones and should pass any emission (even though the pilot is so rich that the mixture screw does nothing)...just plain stock OEM boring carburetion! When I'm feeling another $560 flush, maybe I'll buy an MX, and I can take it through emissions another four times, saturate my hands with gasoline, and throw it away after everyone says: "What did you expect? This is a racing carb!":ride:

It's not the carbs fault that you can't get it to work correctly.

Honestly, it is a carb, fuel and air - not much to it. Jetting sizes from one carb to the next shouldn't be that different. The FCR should flow better than the stock carb due to its design, thus needing more main jet. I know the FCR is complex, I am dialing in one now, but it can be made to work on any large displacement bike.

MGS

[exaresix]

Jetting sizes from one carb to the next shouldn't be that different. The FCR should flow better than the stock carb due to its design, thus needing more main jet. MGS

According to Eddie Sisneros, this is not true. The stock carb is well established to need a pilot jet from 62 to 68. The FCR comes with a 50, and Eddie recommends a 42. There is a big difference between an FCR and the stock carb. in terms of jetting needs.

I don't recall stating it was the carb's fault — only that this carb is not for me in Phoenix, Arizona and I am happy to be rid of it. In fact I'll sell it for half price! Mint condition.

[martinfan30]

martinfan30,

Do you have the FCR MX or the standard FCR with no choke or hot start button?

i have the non choke model, no hot start. three twists of the throttle and it fires up and immediately idles. it works really well.

i

[mgs781]

A variation of the FCR is on every high performance dirt bike made today (KTM, CRF, YZF, KX...). My point is, it could have been dialed in with enough effort. If you didn't want to spend the time, fine... I wish I could have bought the used carb from you, mine cost me $510.

MGS

[exaresix]

Well, I do hope you purchased the MX version.

[rmhrc630]

I finally gave it up! I tried the FCR 41 carb on my xr600r, supposedly the hot set-up. This was not the FCR MX 41, but the standard FCR that Sudco recommends and sells as a kit with cables and bell-housing specifically for the xr600r. Although Sudco maintains that they have jetted it perfectly (50 pilot, 170 main) for the xr600r (with snorkel removed and a medium flow muffler), they are way off. Even with the mixture screw turned all the way in, and using the smallest jet in the "kit" (a 48) it still is too rich to pass emissions testing. The 170 main ran way rich on the dyno/EG analyzer. The carb has no choke, so it's a PITA to start cold, and it is also very difficult to start hot. If you get the bike running, don't stall! The mid-range throttle response was great, and it was hard to give that up, but in the real world, you have to be able to start your bike, and in many areas (e.g. Phoenix), you have to pass emissions. I've now heard that you have to go down to a 42 pilot jet. Who knows where the main should be. The dyno tester in my area told me a 143! I tried that, and the bike was down on power.

If I'd known better I would have bought the MX version that has a choke and a hot start button, but Sudco didn't offer it in kit form for the xr600r, nor did they recommend it. The MX carb alone is $560 and comes equipped with several clear pink vent hoses that some have likened to an octopus on top of the carb. I also notice that Xrs Only has pulled the FCR carb and the kit from their on line sales. I'll bet they had a lot of complaints. When Sudco calls this a racing carburetor, that's what they mean — this $525 non-refundable unit is not suited for the real world. I'm back to the stock carb.

Sorry to hear that XR6.

as you prob know I got fed up with sudco saying the FCRMX would not fit the XR600.

I did detailed measurements asked sudco about 4 times (pleasanlty ignored them) and viola it fitted fine. I specifically did not want the old style FCR as the lack of choke etc I think is unacceptable. I would happily help you figure out how to fit a FCRMX41 to your XR

I asked Burned for jetting specs and he suggested very low pilot - 42 I think is what I have in mine with a 180mj.

My bike starts so easy and revs so well it's not funny. It sit's and idles and just acts like the stock carb till I rev the bejesus out of it - then it goes like stink.

Mine has choke, hotstart and ACV valve and is mega easy to get along with.

I run 2 of the octopus tubes up to the headlight for breathing.

FYI I bought mine on EBAY for $350US plus AUS$90 for the adapter.

The FCR is a huge carb no doubt but it makes the XR boogie.

[NMike]

In Arizona carbon monoxide levels (a measure of how rich the bike is running) need to be less than 5.0 — simple as that. xr600s have no problems passing with the stock carb and recommended jetting. The CO levels with the recommended pilot jet in the FCR are 10.0 with the mixture screw turned in all the way.

? that is 10% of the fume out your tailpipe is raw gas!!!

make sure the float it not too high. some cars here i had to drop the float levels to lean it out. maybe introduce a 'vacuum' leak by means of a hose tapped into the manifold and a small valev at the end.

[exaresix]

rmhrc630,

I've been following your posts, and you sure did the right thing by persisting with the MX idea. I am now fairly certain that Sudco is telling people this simply to get rid of their stock of non-MX carbs. Why they persist in telling people that a size 50 jet is correct is baffling. As I alluded to earlier, I will probably end up getting a FCR MX 41 once I have recovered from the trauma of the obsolete unit I bought. How is the hot-start button working?

[Beyond The Pale]

Be sure to check the choke on the stock carb from time to time. The little flapper is known for break off and get sucked through the engine. It can do a lot of damage. On mine not only the flapper was about to go , the entire choke plate had a crack almost all the way through. That's why I don't have a choke at the moment. Jetted right (68s) it starts easily without it.

[exaresix]

I just spoke with the folks at Sudco, they are sold out of the FCR MX-41 with choke/hot-start. They estimate it will be at least two months before they have more.

[rmhrc630]

rmhrc630,

I've been following your posts, and you sure did the right thing by persisting with the MX idea. I am now fairly certain that Sudco is telling people this simply to get rid of their stock of non-MX carbs. Why they persist in telling people that a size 50 jet is correct is baffling. As I alluded to earlier, I will probably end up getting a FCR MX 41 once I have recovered from the trauma of the obsolete unit I bought. How is the hot-start button working?

XR6 - if I were you I would get one off Ebay - it must be the one with the replaceble housing (ie aftermarket not oem).http://cgi.ebay.com/ebaymotors/HONDA-TRX-450R-KEIHIN-FCR-41-mm-CARBURETOR-KIT-CARB_W0QQcmdZViewItemQQcategoryZ43979QQihZ003QQitemZ130098405725QQrdZ1QQsspagenameZWD1V

Like this:

To tell you the truth I have not used the hot start - never needed to. In fact due to size restrictions (i also fitted e start) there is no room for the hotstart to get turned on.

The choke works however and does exactly what it should.

I owuld not trust sudco - they really dont put enough effort into knowing what their carbs can and cant do.

If you go the FCRMX route then anothe rbonus is the ease of throttle pull. I used CRF450R cables and a 450R throttle tube just to give the big XR a little bit more moderninity.