Keihin 39mm FCR-MX Install, DR650

How long are you going to keep the stock muffler on it?


As short a time as possible! :confused: When could you make it over here?


Originally Posted by motoretro

How long are you going to keep the stock muffler on it?


As short a time as possible! When could you make it over here?

I PM'd you....


Rob what was the year on the Yamaha that you got it out of?

Just to double check, you are saying the carb is from a YFZ, the sport quad?

cant wait! ill search ebay for some now,

i got the yoshi straight pipe, uni airfilter, cut top airbox, de-screened, header ground, so i assume the settings wil be the same since were are both at sea level!!!!!

Just to double check, you are saying the carb is from a YFZ, the sport quad?

YZF450 MX bike?

no, yfz quad


Never seen one of them.

This is such a cool thread. :confused: :confused:

I got to meet my first DR forum member yesterday! Motoretro made the long journey from the other side of the state to check out the FCR-MX set up and ride the bike in stock muffler and FMF-Q2 forms. We did a lot of talking.... OK, maybe I did most of the talking. :confused: But it was good to meet a fellow DR650 rider. The only other dual sport rider I know is my son and you know how those strange DRZ riders are. :confused: I'll let Motoretro give his opinion on how the DR runs... but I'm glad he was able to stay and watch the conversion from stock muffler to FMF-Q2... and ride it afterwards. :confused:

I took some time off of my hectic schedule yesterday(retired)to make a run over MX Rob's place to check out his carb conversion. Right off the bat, I'll mention I've never met Rob before and the following are my views and mine alone.

To give you a baseline on my present ride, It's a 06 DR with a Jesse's Airbox mod, Dyna Jet rejetting kit, K&N Filter w/foam sock, 14 tooth CS sprocket.

After introductions, Rob showed me a FCR MX carb he had sitting on his bench and I actually that thing is huge! How in the world is it going to fit. Then I saw his DR with the same type carb installed, OK it does fill up the space under the tank although seems to look like it belongs there. The tightest clearance was probably at the starter terminal, perhaps 1/4". Rob showed me the adjustments and modifications he did to make this all fit and although the carb is somewhat complicated looking, its not that bad. Plenty of allen fasteners and easy access to make adjustments. I liked that a lot.

Rob had put a stock muffler on to make jetting changes and this was the way I rode it first. Start up was instant and the bike idled very good with neither weak nor lumpy idle, just very solid with no hint of possible stalling. Rob took it out first to warm it up and the bike while quiet with it's stock muffler showed it's power lifting the front wheel in first & second.

I then took the bike and to tell the truth I was really looking for any signs of bogging, chugging or loading up. Bike ran very clean right off idle and pulled very clean through low and mid-range with a very precise feel to the throttle. Where my DR typically levels off, Rob's kept pulling in a very linear fashion. Decel popping was also minimized to the point it didn't bother me.

The increase in power was there although I was really impressed in the way it was delivered.

Next Rob drained the float bowl & changed out the jets and installed the FMF2 muffler. I was able to view the carb with tank, seat & sidecovers removed. The carb really appears to have been designed for the DR. If you did not know better, you would think it came with the FCR. Changing the jets was very quick with tilting the carb one way to change needle positions and the other for main jet replacement. The plumbing all looked factory and the only piece loosened for access was the rear master cylinder. The whole process including muffler replacement took a very short time.

Now for some fun.....In starting the rejetted FMF2 equiped DR the bike idled with a solid sound and feel. I took it out really looking for a hiccup since a lot of things were just changed. The only thing I felt was a slightly softer delivery of power right off idle. The DR pulled just as clean off the bottom and through the gears although now I know why Rob wanted to get the FMF2 back on to ride. From mid-range on up this bike pulls so hard you know it has gained some serious HP. Coming back down the street, I pulled it down to 38mph in 5th without lugging or chugging. Now this feels like a thumper should! Literally ideling up his driveway, the power was very clean & crisp.

I think we all know the initial roadblock to power on the DR was the airbox. Once this was fixed and re-jetted accordingly, most of us were happy although knew the stock carb was still not optimal. In installing the FCR carb with stock muffler intact, the power delivery is now very precise along with a decent power gain. At this point most of us would be satisfied although I feel nirvana is only 30 minutes away. Rejetting the carb and installing the FMF2 has removed all roadblocks i can think of resulting in a seriously strong running DR without getting into the engine. The only downfall I can think of is a louder bike. Rob's FMF muffler has not been repacked in quite awhile so this can be improved on somewhat. A big advantage of such a linear power delivery, you can now short shift through town without concerns of lugging to keep some respect until you get away from the masses and let loose.

In my 2 hour drive home I thought a lot about Rob's FCR carb modification and my riding experience has convinced me this is a great improvement for our DR's

Put me on the list Rob!


sorry to hijack this tread mx-rob but may i know what needle ur using for ur FCR?

Put me on the list Rob!


Thanks motoretro! I'm glad the long drive was worth it to you. It was a pleasure meeting you and sharing so many motorcycling experiences we've both had in the past. I hope I didn't talk your ear off. :confused: I just get so wrapped up into what I'm doing with bikes that I can be a bit hyper. I guess that's why I love racing anything with two wheels. :confused: We have to plan a ride sometime. :confused: Ill, be over closer to your side of the state Sunday at a Motocross track. I gotta ride my new RM at least once this year... sheesh! :confused:

Rob I don't know if you ever looked at the TT DRZ400 FCR-MX Conversion Kit I just found out that my buddy bought one for his DRZ. I looked at it and some of the specs, do you think that conversion kit will work for the DR? Just wondering if you've seen it or not. :confused:

Rob I don't know if you ever looked at the TT DRZ400 FCR-MX Conversion Kit I just found out that my buddy bought one for his DRZ. I looked at it and some of the specs, do you think that conversion kit will work for the DR? Just wondering if you've seen it or not. :confused:

Well you'd have to come up with a cable set up since that carb has the push cable cam already opened up. The jets it comes with in the list are the same ones that came in the YFZ carb.... way too lean! Although I see they throw in the EMN needle. You'd just have to dump the 145 pilot and the main for the correct ones. Next would be the air horn. This carb would have to fit into the same space as the BST so if the adapter that is on the rear of the carb is not the right diameter and length you'd still have to either find the right one or make an adapter. Next would be the vacuum fitting. I know the Black Hawk manifold is what they use to mount the regular FCR to the DRZ. It has the spot for the vacuum fitting. The problem with that is it most likely would be longer than the stock DR650 rubber manifold and the FCR-MX would not fit using it in the DR's frame. That leaves doing the same mod I'm doing for the vacuum petcock.

So in digest: You'd have to either make an adapter for the push cable, find a custom cable or find some oEM cable that might work. the DR has a pretty non standard throttle assembly so the adapter might be the best way to go.

You'd have to purchase the proper jetting.

You would have to find out the total length spigot to air horn to see if it matches the BST and find out if the air horn diameter is right for your air boot.

You'd have to mod the carb like I've done to provide the vacuum for the petcock..... the guys that have plastic tanks and regular on/off/reserve petcocks not included.

Not exactly "bolt on and ride away" kinda stuff but doable for the industrious. :confused:

Hi Rob,

I was wondering what the Lambda sensor came from that you are using for your mixture meter and where you may have the sensor mounted? i just remembered this morning that in my shed i have a control unit from one of my LP Gas conversions that has the meter built in so i only need to mount a O2 sensor in the system,Any pics?:confused:

Best regards


mx_rob, good stuff with the carb swap. I wonder if I might bend your ear a bit. About 10yrs. ago I had a DR350 that was a pig to kick start and had the usual CV carb afflictions. I did some research to install a smaller dia. round slide Mikuni to hopefully partially emulate the wonderful engine characteristics of my one kick, down low chugging, 2 barrel carbed XL350R. This was before the WWW (at least for me) and I could not get all the info together. I'm seriously thinking of taking another run at it with the 650.The objectives would be: more low down torque at the expense of higher rpm power (the engine never sees more than 80% of max. revs.), the ability to easily pull 16/42 gearing and better fuel economy. In theory this would be accomplished by: smaller dia. (36-38mm?) round or flatslide non accel. pump carb c/w new matching manifold, aluminum transitioning spacer between manifold and head to increase intake tract length and possibly cam degreeing. Any and all thoughts greatly appreciated from everybody. Thanks, Berni

D'OH! I just hijacked your thread mx-rob. A thousand apologies. Can my previous post be moved or deleted? Tanks,b

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