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FCR or FCR-MX-which one?


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I am extremely frustrated with my stock CV carburetor:banghead: and am about to make the leap into an FCR Carburetor but do not know which set up to get (or exactly where to get it). Does anyone have a website that you would recommend ordering it from? I have the following:

Altitude: 750ft

’09 XR650L

Uncorked

Hot Cams Stage 1 Cam

FMF Power bomb Header

Supertrap Muffler (12 discs)

Unifilter………..etc.

The options (I think) are as follows:

FCR or FCR-MX

It is my understanding that I don’t need all the extras like Hot Start, Choke,Throttle Position Sensor, etc.-Just a “plain” FCR Carb. What is the difference between the FCR and the FCR-MX (on Supco the FCR-MX is about $50 cheaper). I don’t want to cut myself short but neither do I want to get an option that I don’t need. If you could be so kind to help me out it would be greatly appreciated, I am lost:smirk:. Thanks!

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Go with the FrcMX , it's more easy to tune some things compared to "old style "Fcr .

On the FcrMX you can adjust the ap way easier than the other .

Sudco told me yesterday that I could not use the MX on my XRL because it is way too big. They won't even sell me an FCR-MX (they say there isn't one for it:banghead:). I also called XR's Only who said the FCR is way too touchy and you always are having to adjust it to get it to run right. They sell the Mikuni carb and say they are way better. Talk about confusing!! Your thoughts? Anyones thoughts?

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Another question, would there be a difference between the standard FCR and the FCR-MX. Supco really hesitated when i asked for the FCR-MX. They even told me they would'nt support it on XRL and the only one they would support would be the standard FCR. Do I really need the MX model? They tell me the standard (just plain) FCR would bolt right up and be set close enough to run fairly well. They told me to call them after I installed it and they would help dial it in:thumbsup: Anyones thoughts?

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Not certain why they are recomending the non MX but either are quite workable, the difference is the FCR was designed for an application where the carb is tilted forward maybe 20 to 30 degrees, but will work upright as well. The MX was designed for more upright application as single cylinder bikes usually are

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I think they recommend the old type Fcr simply because Sudco has a ready bolt on kit for this bike .

Could be, but, they were even hesitant to sell me the MX. They also told me they would not help me set it up since it wasn't for the XRL. That is big since I will need help setting it up:banghead:

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  • 1 month later...
I have been running an FCR MX on my XRL for a few months now and it has proven to be solid as a rock. No glitches whatsoever.

I also installed a FCR MX-40mm, on my 97 XRL a few months ago, off of a 04 crf450r, bought, won off ebay, $120. as THUMP says, mine has been great also, no problems at all, in fact, it's the best mod i've done. The carb was jetted at, 170mj, 45pj, ncyr needle. the xrl feels stronger through out the rpm's. she now has a top end hit, that it didn't have before. it's even running 10 deg cooler on the highway at 70mph, 210 deg. I've read that 39-40-41mm fcr's will work just fine on the xrl.

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It is my understanding that I don’t need all the extras like Hot Start, Choke,Throttle Position Sensor, etc.-Just a “plain” FCR Carb. What is the difference between the FCR and the FCR-MX (on Supco the FCR-MX is about $50 cheaper). I don’t want to cut myself short but neither do I want to get an option that I don’t need. If you could be so kind to help me out it would be greatly appreciated, I am lost:smirk:. Thanks!

You don't need the TPS nor the hotstart but the choke is a nice option if you live in a colder climate but not absolutely needed because you just have to snap the throttle a couple times and the AP pump acts like a primer. I just unscrewed the choke out of my stock CV carb and plugged it right in my new FCR-MX carb. The cable is a little taught but works really nice. It acts like a fast idle to let the engine run a couple minutes before riding in the morning.

I put an OEM FCR-MX (even newer model that the MX Sudco sells) that I got off ebay with all the options (TPS,hotstart,choke) for $380 +plus NOSS Adapter ($65) and throttle cables ($65). It has a revised AP pump linkage that does not need the o-ring mod. I used a NOSS adapter to fit it to my XRL and custom throttle cables from sudco. I did a quick search and found 2 for sale for $320 just like mine.

Here is a write up on my installation First WriteUp and Final Report, here are some Mods that I've done to it. I had a write up here but since they went back to the old format that post is no longer here.

What problem are you experiencing ? A properly setup cv carb should be a better general solution than the FCR.

A properly setup CV should be better, yes I completely agree, but IMO to say that its better than a FCR is just plain wrong. The AP pump on itself is worth the upgrade and makes a HUGE difference in throttle response.

Edited by D0T-C0M
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Here is a write up on my installation First WriteUp and Final Report, here are some Mods that I've done to it.

Very nice writeup and good info!

Just FYI: The carb is a FCR MX 40 (not a 41), from a 2007 CRF250R. You can check the serial number, and/or measure the carbs venturi.

I can guess from who you bought it. I informed eBay some time ago since the guy was misleading people; he stopped selling them now.

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I had measured the inside diameter of mine and it measured 41mm and the stock jetting that came with it did not match up to any suzuki,yamaha or honda when I checked. Out of curiosity PM me the ebay user and I'll check to see if its the same person.

Edited by D0T-C0M
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I had measured the inside diameter of mine and it measured 41mm and the stock jetting that came with it did not match up to any suzuki,yamaha or honda when I checked. Out of curiosity PM me the ebay user and I'll check to see if its the same person.

Well, remember you have to measure the inner diameter at the throttle valve, where the venturi is at its smallest. A common mistake is to measure at the inlet or outlet of the carb (where, off course, it has a larger diameter).

There are many differences between the CRF 41mm and 40mm carb. If you're interested, I can list them.

The 07-09 CRF250R are the same carbs, where the 07 has serial # 01D***, the 08 has 01E*** and the 09 has 01F***. All CRF450R carbs have 00A*** etc. as serial number. Only the 07/08 CRF450R carbs are 41 mm carbs (remember the 09 CRF450R has fuel injection).

I will also PM you the name of the eBay seller.

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There are many differences between the CRF 41mm and 40mm carb. If you're interested, I can list them.

Yes I measured at the engine side of carb measured at the end not near the throttle body so you could be correct. You are correct about the seller you PM'd me, that is the person who sold me the carb. When I received my carb I tried to cross reference the jetting to the honda stock jetting using online parts list from babbit and found nothing close to what I had installed. I'll check the part numbers to see if what you posted corresponds to what I have.

Please list the differences. I know that there are some differences between my carb and Sudco's FCR-MX carb, the main one being the AP pump linkage and diaphragm, the float bowl and the needle has a only 5 grooves instead of 7 and has a longer tip above the grooves. What are the differences between Honda's 41mm and honda's 40mm?

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Please list the differences.

You indeed have the carb with the new AP linkage (O-ring mod not needed anymore) and diaphragm.

The 07/08/09 CRF250R and the 07/08 CRF450R carbs have these.

The 04-05 CRF250R carbs have 37mm, the 06-09 have 40mm (2010 and up have EFI).

The 02-06 CRF450R carbs have 40mm, the 07-08 have 41mm (2009 and up have EFI).

The differences (external) between the 40mm and 41mm carbs are:

- serial numbers (obviously)

- the 40mm carb measures about 41.2mm at the intake (40mm at the throttle valve)

- the 41mm carb measures about 42.2mm at the intake (41mm at the throttle valve)

- the top cover with the extra small cover to access the needle is on the 250R/X carbs only. The 41mm carb has a cover with a small lump in it. The 40mm CRF450R carbs have a 'flat' cover.

- the TPS connector of 450R carbs is different from that of the 40mm carbs (the 08 450R carb does have the same)

- the TPS on the 250R/X carbs is routed differently

- ...

To tell you the exact internal differences, I should open them both, but I have no 41mm carb at the moment. I do have pics of both carbs to clarify, but I'm not at home right now :bonk:

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