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TM-40 Mikuni OR Kienin 39 FCR-mx?

By mattheritage,
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mattheritage

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Not sure I spelled those right....

Anyway, Im REALLY thinking about changing my carb out. I'm not sure which one to go with though. Here is my dilema...

I recently moved and sold my house. I'm renting a little place and no longer have my shop ?. So fabbing parts, and doing complicated projects is pretty much out for me. :ride:

My big question is... which of these carbs would be better? I can get the blt on kit Mikuni from Jesse for $375. Or I can get that old FCR-mx on ebay that needs some TLC for $200. IF It's still there. If its not I see some for $299. But they arent bolt on.

So is the FCR-mx mod better than the Mikuni carb? Would I even notice a difference? Which would be best for changing a lot of altitude or would it matter?

I'm kind of liking the idea of a bolt on deal considering my present circumstances. But if the FCR is way better I'll find a way to getter done.

Thanks!

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Paul in SF

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Hmmm... I hate decel popping. This may be a deciding factor. Is there a way to adapt the mikuni with a decel valve I wonder.... If I set it up right though, decl pop should be minimal right?

My Mikuni hardly pops at all. I was worried that it would be a problem when I decided on the Mikuni. But it turned out not to be an issue. I went with the Mikuni due to the plug and play of installation and set up compared to the FCR ... ?

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mattheritage

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Actually there's quite a it more to it than that... hence the reason nearly all major MC/ATV mfgs use (or used before FI) the FCR-MX on their performance four strokes. :excuseme:

Hey Rob, I bit the bullet and made an offer on a FCR-MX on ebay that the guy says is set up exactly like your instructions say. Would you mind checking out the listing and telling me if this is what I need for sure, and if it sounds like it is set up with everything I'll need? If you dont have time that's cool too. I already made the offer and will make it work (hopefully) either way. :bonk:

http://cgi.ebay.com/ebaymotors/96-2010-DR650-EXCELLENT-MUST-HAVE-MOD-FCR-MX39-CARB_W0QQcmdZViewItemQQhashZitem3efa198a27QQitemZ270483950119QQptZMotorcyclesQ5fPartsQ5fAccessories

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Grand Master

mxrob

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Hey Rob, I bit the bullet and made an offer on a FCR-MX on ebay that the guy says is set up exactly like your instructions say. Would you mind checking out the listing and telling me if this is what I need for sure, and if it sounds like it is set up with everything I'll need? If you dont have time that's cool too. I already made the offer and will make it work (hopefully) either way. :excuseme:

http://cgi.ebay.com/ebaymotors/96-2010-DR650-EXCELLENT-MUST-HAVE-MOD-FCR-MX39-CARB_W0QQcmdZViewItemQQhashZitem3efa198a27QQitemZ270483950119QQptZMotorcyclesQ5fPartsQ5fAccessories

That's a bargain! It has my standard jetting for sea level to 2000. You can't beat the price! :bonk: It looks like he has my instructions printed out in the background so it should be plug and play. You can always reprint the install instructions off my site if you need them.

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brianwheelies

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I went with the FCR-MX initially and found it to be noisy and big. It worked well though and has all of the bells and whistles you would expect from a modern carb.

I found myself burning through a lot of gas after a while though. Ran out on one occasion. I sold the carb and the next time around I will go for the TM-40. It is simpler, smaller, and won't have the clackety clack of the FCR-MX. It also won't have a ball bearing supported slide which is a bit of a bummer but it still works.

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mattheritage

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Well I bought the FCR-MX 39. Hopefully it's everything the guy says it is. I'm pretty stoked to get it installed. Even though I cant really ride except maybe a day or two here and there (and even then its COLD). Plus the bike only has 350 miles on it so I still have to be gentle with her. Sigh....:excuseme:

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neskipper

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You will not be disappointed! After buying my 2007 w/24 miles on it a few months back I have been reading this site. Well a GSXR can, open airbox, FCRMX from ebay and some work easily performed thanks to MX Rob's detailed instructions. HOLY COW! The difference to me is so night and day I can't believe it. I'm also pleasantly surprised how slow I can go in first even with the stock gearing. I purchased a 14T CS but wanted to leave the 15T on for a comparison between the stock exhaust/BST40 and the FCR/GSXR can. There is no comparison. Thanks MX ROB! :excuseme:

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JP4

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Actually there's quite a it more to it than that... hence the reason nearly all major MC/ATV mfgs use (or used before FI) the FCR-MX on their performance four strokes. :excuseme:

I`m curious. I don`t care about all the technical mumbo jumbo, but is the FCR-MX a better carb for the DR, than the Mikuni TM? The DR isn`t a super hi-tech, 14K rpm revving mx bike, that generally isn`t micro tuned for elevation and atmoshpheric conditions.

Isn`t the simplicity and plug and play convenience of the Mikuni better suited for most DR owners - who by the way - do their own maintenance, without the benefit of dynos and A /F meters?

Beyond all the above, what specifically, are the real world ride benefits of the FCR-MX?

Just curious. Thanks,

Jason

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ProCycle

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Here from an old thread on the same subject.

Each carb has both good and bad attributes when compared to the other. The FCR is a more advanced carburetor but that also makes it a more complicated piece of hardware as compared to the Mikuni. The Mikuni is very simple and straightforward to make jetting changes. The FCR has the 'coast enrichener' that will decrease (but not eliminate) the annoying popping on deceleration. The TM40 will pop just like the stock BST. The TM40 (kit) is a brand new carb and therefore a known quantity. Most FCR conversions will start out with a used YFZ450 carb of maybe questionable history.

If you can score a good deal on a good FCR then you can do the whole conversion for less money than the full TM40 kit. In my opinion the FCR is more suited to the guy who is more of a hands-on tinkerer. Someone who is not afraid to delve into a used carb, modify and re-jet it and evaluate the sucess of his efforts.

The TM40 (kit) is probably a better choice for the guy who feels comfortable swapping out carburetors but doesn't really want to become intimately familiar with internal carburetor parts.

If we were talking about putting these on some other bike - say a hot rodded CRF450 flattracker then the FCR has a clear advantage because there is a lot more tuning components and tuning data available to make the FCR work in a very wide range of applications. In comparison the TM40s tuning range is quite limited. It just so happens that the tuning components available make it a happy match for the DR650.

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neskipper

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I`m curious. I don`t care about all the technical mumbo jumbo, but is the FCR-MX a better carb for the DR, than the Mikuni TM? The DR isn`t a super hi-tech, 14K rpm revving mx bike, that generally isn`t micro tuned for elevation and atmoshpheric conditions.

Isn`t the simplicity and plug and play convenience of the Mikuni better suited for most DR owners - who by the way - do their own maintenance, without the benefit of dynos and A /F meters?

Beyond all the above, what specifically, are the real world ride benefits of the FCR-MX?

Just curious. Thanks,

Jason

This is just my opinion but for me the "real world" benefits of the FCR over the TM were:

1. The FCR was more available on Ebay.

2. No need to change the throttle cables.

3. The cost to do the swap was considerably cheaper than buying a new kit.

4. Simple to swap back to BST40 if need be.

As far as performance differences between the two, I cannot comment.

Cost for me to go from BST40 to FCR is:

1. Carb from Ebay, 110.

2. Jet kit from ProCycle for FCR conversions, 24.95

3. FCR fuel mixture screw so I can adjust while on bike, 13.99

4. Aluminum pipe to machine adapter, 10.00

5. Tank petcock from Raptor without vacuum line. 16.00

I had access to a lathe to turn the aluminum so the whole carb swap cost me 175 bucks. Since I decided to eliminate the vacuum petcock the conversion was much simpler.

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ProCycle

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Wait... I guess Missed the whole vacuum petcock deal. I have to put a new petcock on my tank too? Can I just put the stock petcock in the prime position?

The FCR doesn't have a vacuum port. Yeah, you could just turn it to prime if you don't want to drill and tap the carb for a vacuum source.

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