FCR MX 41 float weight spec and part vendors needed

Does anyone know the proper weight reject specification for the float in a Keihin FCR MX 41, which my 2007 FE550e came with?

Or perhaps some kind soul has a new one and will weigh it and reply?

I am used to defining float serviceability reject criteria by weight, as per automotive/commercial/industrial type service. Plastic/pheholic floats would slowly absorb fuel as a function of age, redering them useless. Or, if you go real old school, if the carb float was brass, you shook it and listened for fuel inside the orbs. Brass floats are cooool IMO.

Also, any preferred vendors for parts that you use. I need all the gaskets/orings/elastomers and a few hard parts. %$%@#ing expensive they are.

Thanks.

Thanks ElSnorro.

For vendors, I have:

1) frank mx parts
2) JetsRus
3) keihin-fcr.com

Now I just need that float weight.........

How do I identify which needle valve seat I should order? There are many of them listed.....

husabutt said:

If you take yours out and look at it with a magnifying glass it should be stamped with a number such as 3.8

Click to expand...

It was, and the stamped numbers were tiny.....

Thank you husabutt, that was a solid tip.

I cannot find a vendor that sells the mid body gasket for my FCR. Any help is greatly appreciated.

Husabutt, thanks for the reply.

I realize that FrankMXparts, JetsRus, keihin-fcr, tokyomods, etc., sell these type of parts, aftermarket, for the FCR. I have checked all of those vendors, they do not sell the mid body gaskets that my FCR needs.

Neither of the gaskets in the pic you posted are the correct gasket for my FCR.

Which is why I stated "I cannot find a vendor that sells the mid body gasket for my FCR."

Does anyone know of any other vendors that sell these gaskets?

Or where I can find a comprehensive listing of all FCR MX "generations" information? Basically, a manufacturing history that correlates the ID number stamped/etched on the mid body flange to the parts contained details.

Thanks in advance.

husabutt said:

Keihin doesn't sell them. You have to go aftermarket.

https://www.ebay.com/itm/Mid-body-gasket-kit-1-Keihin-FCR-MX-carburetor-o-ring-repair-37-39-40-41/190756145774?epid=21002491013&hash=item2c69f3ca6e:g:ELsAAOSwOlJZ0gzY&vxp=mtr

Click to expand...

I thought as well. I have a new one on hand. It is waaaaaay off. Cut and splice it in multiple places off. The upper gasket is not correct for my carb either. The biggest tell for both is the o-ring that is molded into the gasket, and where the 2 intersections to that circle occur. And, the 2 inner sealing oval(s) are dimensioned wrong. And that "kit" is missing 4 small o-rings and another molded o-ring "bubble" gasket for the part that the slide straddles (called the slide tower), all of which are needed when you disassemble the carb at this flange. JHFC...

It's %$#@$$%$@ing frustrating that it's this hard to buy the correct gaskets (molded o-rings) for this $@@##@#$ing carburetor. At the $$ this stuff goes for, it should be extreeeemly easy to get it all exactly right. IMO.

I'm pretty sure those are photographs of gaskets.

I have emails out to 7 vendors that sell such, maybe I'll get lucky with an ID from one of them.

husabutt said:

As far as I know there were only 2 generations of the FCR. The original Flat CR (had no choke and was originally designed for multi carb street bike usage) and the FCR MX.

The lower gasket in the drawing looks correct to me for your usage. Parts drawings are never spot on.

A good part of my day is spent writing auto collision damage estimates and it is almost appalling how bad some of the parts drawings are in the estimating guides.

Click to expand...

Documentation, hope it helps someone.

1. All of these images make for good reading prior to rebuild: http://www.pbase.com/jdjetting1/keihin_fcr_manual_views&page=all
2. This post makes for good reading prior to rebuild: http://www.djhcyclesport.com/carb101
3. As does this one: http://ktmtalk.com/showthread.php?171766-AC-Pump-101
4. Most of the exploded diagrams for this carburetor on the www are fuzzy as hell. This one is clearer: http://216.104.185.253/images/carburetion/FCR-MX.gif
5. The following vendors sell Keihin FCR MX parts, direct to users, in the USA:
a. Tokyomods.com
b. Jetsrus.com
c. Jdjetting.com
d. Frankmxparts.com, they ship out of the Netherlands, and list most of their parts on eBay.
6. IMO, the best kit value is this, but it does not reseal the mid body. At $50 it is a good value: https://tokyomods.com/shop/fuel-air/fuel-air-keihin-carb-parts/tokyomods-carb-o-ring-kit/
7. There are many mid body gasket “kits” available. The “Athena Gasket Kit for Dual Spray Venturi Jet Kit P400 000 500 001” is $20 on Amazon, it has both of the currently available mid body gaskets plus the rectangular o-rings for the bowl vents, but you do not get the bubble gasket.
8. Make sure that the tiny orifice in the accelerator discharge nozzle jet is clear. I stuck a vacuum hose on it, dipped it in soapy water and blew soap bubbles to check mine.
a. This small brass part is not shown on any exploded diagram that I have found. It is shown here, upper split half, the slotted brass circle: http://www.pbase.com/jdjetting1/image/75676627
b. and here: http://www.pbase.com/jdjetting1/image/130398239
c. and here: http://www.pbase.com/jdjetting1/image/130366629
d. Although it has a screwdriver slot, it is not threaded into the carb body. At least, mine wasn’t. It’s a light interference fit.
9. If you have a FCR MX that has a removable (with 2 screws) inlet funnel (the flange that connects to the air filter boot) you cannot, as of this writing (11/20/2017), buy the correct gasket to reseal the mid body flange. You have to buy a gasket that partially fits and modify it. All of this is documented pretty well by jdjetting.com starting at this image: http://www.pbase.com/jdjetting1/image/140910519
10. The mid body flange gasket consists of a perimeter seal with 2 oval partitioned seals inside of and attached to the perimeter seal, and the slide tower uses a bubble seal. The 2 vent towers use rectangular o-rings.
11. I’ve read the threads detailing repairing the wheel grooving caused by the throttle valve. And some guys shim between the plate and the valve. My carb had no wheel grooving in it (well, maybe 0.002”). IMO, all you need to do is:
a. Make sure that no part of the throttle valve, without the vacuum release plate, touches/drags on the engine (downstream) side of the rectangular cross section bore that the throttle valve reciprocates within. Hold it horizontal, to the light, stroke the valve through its range of motion, observe.
b. Make sure that the vacuum release plate sliding surface is smooth. Mine was not. I surfaced mine on a glass plate with a piece of 600 wet or dry. It didn’t take much.
c. Make sure that the carburetor surface that the vacuum release plate slides on is smooth. Mine had long scratches from use. I surfaced mine using a 1/16” piece of steel plate with a piece of 600 wet or dry. It cleaned up quick.
d. Perform b. and c., above, to improve the seal and minimize sliding friction between the 2 surfaces, not to perfect them.
e. Make sure your vacuum plate lip seal is intact and properly oriented: http://www.pbase.com/jdjetting1/image/133895321
f. Be careful not to install the vacuum release plate upside down, which is possible. The hole goes down.
12. A new Keihin FCR MX 41 float, part number 1052-856-2100, (SKU # 018-202) weighs 12 grams.
13. Check the accelerator pump spray pattern dynamically before installing the carb. The spray stream should be decently centered in the tunnel, it should not hit the throttle slide, it should start and stop as per your desired timing, it should refill properly, etc.

To be continued.....