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Keihin 39mm FCR-MX Install, DR650

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You know what should be great about this kit, wind not introducing intake turbulence. I know my bike is a bit on the lean side at the moment and I'll work on dialing it out but the hopes are that this setup, since it's not vacuum operated slide, will have none of the BST's downfalls.

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You know what should be great about this kit, wind not introducing intake turbulence. I know my bike is a bit on the lean side at the moment and I'll work on dialing it out but the hopes are that this setup, since it's not vacuum operated slide, will have none of the BST's downfalls.

Hopes? There's no chance of the FCR experiencing the surging/windage issues suffered by the BST. The only thing the wind packing into the air box with the FCR does is increase performance.... quite the opposite of the fight between air box pressurization and the diaphragm vent on the BST. :confused:

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Rob, I thought your other jetting thread was good news. If you get the kit set up I want one! Great work. Do you think us high altitude guys will need different jets for all circuits? Sounds like the pilot may have enough adjustment.

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Rob, I thought your other jetting thread was good news. If you get the kit set up I want one! Great work. Do you think us high altitude guys will need different jets for all circuits? Sounds like the pilot may have enough adjustment.

So far it looks like I'm leaving you nose bleeders 4 clip positions on the needle if you are using a performance exhaust system. I'm thinking the stock muffler may require a clip leaner on the needle at sea level.... so then you'd have 3 left but I don't actually have data yet on this. I think the pilot is also small enough as is. You'll just have to make some adjustments and drop a main jet size or two. :confused:

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OK you speed demons. Michigan finally gave me a break today in the weather department so I could continue testing. Today was blitz mode even though it was a bit windy. I have to take whatever good weather I can in this state. Remember I'm running 14/52 gearing. In my Needle Comparison thread I think my highest recorded top speed was 104mph. I topped that by 6mph today! 110 indicated.... but after a few frantic freeway runs what was the best part of riding back to my garage? The in town smoothness. It's just amazing how steady the engine will thump down without a hicup. I did some more slow speed 5th gear testing and I was able to run the bike all the way down to 34mph indicated without any nasty bucking or kicking. The reason for this is the low rpm thump-thump-thump pulses of the intake no longer effect slide position like they do on the BST. Think about what convulsions your slide is going through on the BST at low rpm. The intake valve is only open for one of the four cycles making vacuum.... the other three cycles the slide is falling back down... maybe even bottoming out before being lifted back up when vacuum is applied to the intake port again. The slide is just jumping up and down to beat the band at low rpm. With the direct acting slide all of these girations are gone. The bike is a pleasure to go slow on now.... you can lug it right down to counting the thumps and short shift to 5th gear before you even hit 40 mph.... Oh yeah, and it hauls *ss too! :confused:

So, I've tested all 4 of the needles that I thought had a chance of working... and the stock YFZ450 needle which was waaaaay too lean. It looks like the EMN is the needle. The 50 pilot is performing perfectly with no lean run-on even after hammering the thing on the freeway. The 100 slow air jet is perfect and the YFZ450 carb has a pre-set main air jet which, according to Sudco, is a 200 and is the right one for the DR650. There are no throttle range issues anywhere that I can detect and I've tried some ugly stuff that most riders aren't likely to do to their beloved DR. At two turns out there is still at least another turn out in richness and plenty of turns in to lean it out. The 168 main is working the best with my set up. Modded box, no screen, TwinAir filter, ground head pipe weld.

Next is bolting the Buick (stock muffler) back on the bike, once my new head pipe/muffler joint gasket arrives, to finalize the setting for it. :confused:

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Remember I'm running 14/52 gearing. In my Needle Comparison thread I think my highest recorded top speed was 104mph. I topped that by 6mph today! 110 indicated....

***! geared down that low & still get up to that speed?

what RPM do you reckon its turnin?

i'm running 14/42 and could swear its only doin 80 almost topped out

but with no speedo, i'ts seat of pants

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Remember I'm running 14/52 gearing. In my Needle Comparison thread I think my highest recorded top speed was 104mph. I topped that by 6mph today! 110 indicated....

***! geared down that low & still get up to that speed?

what RPM do you reckon its turnin?

i'm running 14/42 and could swear its only doin 80 almost topped out

but with no speedo, i'ts seat of pants

Remember this is indicated not actual. Like most jap bikes the speedometer is overly optomistic to say the least on the DR650. There are lots of posts on this in the forum.... I've seen anything from 7 to 10% out of whack posted. I think I'm very close to the rev limiter at that speed.

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What he said... the speedo is off about 10%. On my 02, 55 indicated is dead-on 50mph on my GPS.

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I got a voiemail from my local Suzy shop that the stock muffler seal is in. Hopefully I'll get out of work early enough today so I can pick it up. If so, I can have the jetting finalized this weekend. I hope I guessed right in my original jetting range that I ordered for the two-ton-tony muffler. :confused:

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hi rob, great thread mate, looks like you are about to cost us more money mate, one thing i would like to ask is why did you choose the fcr-mx 39 and not the fcr 39, i was told by a bike shop that the only difference is with the mx is the hot restart button and a few other little things, and if i was going to do this mod the fcr would be enough, and not to worry about the mx.....

please set me straight as i dont know what road to go down now mx or just fcr....

thanks in advance mate...

cheers tony.....

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hi rob, great thread mate, looks like you are about to cost us more money mate, one thing i would like to ask is why did you choose the fcr-mx 39 and not the fcr 39, i was told by a bike shop that the only difference is with the mx is the hot restart button and a few other little things, and if i was going to do this mod the fcr would be enough, and not to worry about the mx.....

please set me straight as i dont know what road to go down now mx or just fcr....

thanks in advance mate...

cheers tony.....

I chose the MX for a number of reasons.... It has a larger capacity float bowl with jet baffling to prevent fuel starvation on rough terrain. It also has multi-point venting. The carb mechanicals are fully enclosed... no external moving parts to be fowled by mud and sand like on the regular FCR. This particular MX has the air-cut valve to reduce decel popping on straight through exhaust systems. :confused: As far as the extra cost goes.... you'll forget all about it after a short ride. :confused:

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OK, here we go boys and girls. Jetting testing is done! :confused: The Buick (stock muffler) went back on late this morning and I threw in the jetting I expected to do the job. It did! The A/F monitor ran exactly where I like it to run... just one LED into the green rich side. So it's a 162 main which is two jet sizes leaner than the open pipe 168. The same EMN needle with the clip put back in the middle position. I do have to clarify that this needle has 7 clip positions so when the clip is in the middle it's actually in the 4th clip position. I posted when I was doing the FMF Q2 settings that I had to raise the needle(lower the clip position) to the 4th clip position before... it's actually the 5th position. My bad. I didn't touch the air screw which was at 2 turns out. You'll have plenty of room to try and eek out the most MPG's and adjust for high altitude in everything but the fixed main jet size.

First let me answer Brianwheeles about his jet changing question. It's a cake walk! No need to remove the carb to change the main jet or the needle! You don't even have to remove the throttle cables like you do on the BST. Sweet! Remove: side covers, seat, vacuum petcock line from tank, fuel line from carb and remove the tank. Remove the bolt for the rear master cylinder reservoir (for a little more swing to the right), loosen the air boot and manifold clamps. Open the cool little allen head drain bolt on the float bowl and let the carb drain. Swing the carb to the right and remove the 17mm main jet access plug. A standard 1/4" drive 6mm socket and a ratchet fits perfect. Change your jet and put the access plug back in. Easy! Swing the carb to the left and remove the two allen head cap screws that hold the carb cap on. Open the throttle which brings the slide to up to the top. There is a allen head plug in the center of the slide which you remove to access the needle. It has a cool little spring and brass washer that are attached right to the plug that hold the needle firmly seated. The needle is in a recessed pocket under this plug in the slide. I used a small piece of vacuum tubing to slide over the needle to remove it. You could also grab it with a very small set of needle nose pliers. Change your clip and drop it back in and install the plug, cap and two cap bolts. Easy! Everything is o-ringed so no need to change gaskets. :confused:

Now you probably want to know how she runs with the stock Buick mounted up right? Well, there's no getting around the HP/torque you are giving up with the stock muffler. It is very evident with the stock carb... and even more evident with the FCR. The jetting tells the story. Not that the many benefits of the FCR go away with the stock muffler... they just are not as pronounced... especially the further up in the throttle range you go. It's still dead smooth in town, will run right down to counting thumps and responded well to throttle inputs. Torque is still way better, but as the throttle opens and the flow increases the stock muffler's flow limitations restrict the upper mid range and top end. For instance, taking off from a dead stop the engine pulls hard but drops off much sooner with the stock muffler. It still smokes the BST everywhere... but if you ride the bike with the stock muffler and then try a Q2 or other high flow pipe with the proper jetting you won't want to go back.

Now I have to do some work disassembling, cleaning and inspecting the three FCR-MX's that I have to convert. My jetting is ordered from Sudco and should be here next week sometime. I will also start working on complete installation documentation for the carb with pictures and arrows... not sure about the flashing lights but I'll give it some thought. :confused:

I think someone must have hit the Easy button for me on this project... The BST was far and away harder to get set and adjusted to my liking. I think Keihin was the button pusher. :confused:

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what year did the carb come off of? might be easier to send the carb to you to be setup?

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I chose the MX for a number of reasons.... It has a larger capacity float bowl with jet baffling to prevent fuel starvation on rough terrain. It also has multi-point venting. The carb mechanicals are fully enclosed... no external moving parts to be fowled by mud and sand like on the regular FCR. This particular MX has the air-cut valve to reduce decel popping on straight through exhaust systems. :confused: As far as the extra cost goes.... you'll forget all about it after a short ride. :confused:

hi rob, thanks for clearing that up mate.

so when i order the fcr-mx39 from the bike shop is it the same as yours even though you got yours out of the yamaha

cheers tony.....

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With the stock muffler in place, Does the air cut valve eliminate or minimize the decel popping? Has there been any issues with starting hot ot cold? are there specific makes & models other than the Yamaha 450 mentioned earlier that use the same carb?

Thanks,

moto

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With the stock muffler in place, Does the air cut valve eliminate or minimize the decel popping? Has there been any issues with starting hot ot cold? are there specific makes & models other than the Yamaha 450 mentioned earlier that use the same carb?

Thanks,

moto

The air-cut valve only minimizes decel popping. I was hoping for complete elimination but I guess it was too much to expect. It's a lot quieter on my bike with the Q2 but on hard decel at rpm it's still there... not as loud but still present. No starting issues at all. This model does not have the hot start knob but it is unnecessary with electric start anyway. Any 39mm FCR-MX would fit but the YFZ450's carb has the blank casting for the push cable that allows me to modify it for the stock DR cable. I also wanted the 39mm carb for the reasons I've already stated above and on my web site. I think the YZ450 MX bike uses a 39mm also but you'd have to come up with some type of adapter for the push cable, get cutom cables made or just replace the throttle assembly and cables with ones that came off of the bike you got the carb from. Another issue might be the air horn. The one on the YFZ is fairly easy to make an adapter for because it's smaller than the DR's air horn. I'm not sure if all the cast on OEM air horns are the same. You might want to inquire as to the diameter before purchasing a carb. It would have been more expensive to do if it needed to step down or do other girations to get it to fit. :confused:

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hi rob, thanks for clearing that up mate.

so when i order the fcr-mx39 from the bike shop is it the same as yours even though you got yours out of the yamaha

cheers tony.....

No, if you don't buy the OEM YFZ450 carb you'll have to make adapters or replace the cables and figure out what to do with the air boot adapter. All of the aftermarket Keihin's have bolt on air horns. Sudco was only thinking they might have one that works with the MX version since they've never actually installed one on a DR650 before. They may have one that will work but we don't know for sure. It should be fairly easy for them to measure out the BST and find an adapter that produces the right diameter and overall carb length so that the FCR-MX fits in the same space as the BST. That was my plan to investigate while I was measuring things up to see if the carb could be mounted on the bike... but then I got the brain storm to find a used carb and mod it on my own. :confused: Yamaha's price is $612 for the carb and then you'd still have to do the mods and jetting. The only advantage to the $575 Sudco carb is that you might not have to make the air boot adapter if they have one that will fit the DR650.... but you will have to do something different than what I did to get the DR's push cable to work. :confused:

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Yamaha's price is $612 for the carb and then you'd still have to do the mods and jetting. :confused:

Any chance you can buy new carbs from a discount house dealer for a better price? perhaps they will also give you a quanity discount also....Sudco might give a bulk discount also if you were ordering jets for 10 carbs at a time.

Might be a easier sell to DR riders if the carbs were all new, ready to bolt on, pre-jetted & modified.

I'm interested in one set up for stock muffler, Drivability is more important to me than all out power.

Moto

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Any chance you can buy new carbs from a discount house dealer for a better price? perhaps they will also give you a quanity discount also....Sudco might give a bulk discount also if you were ordering jets for 10 carbs at a time.

Might be a easier sell to DR riders if the carbs were all new, ready to bolt on, pre-jetted & modified.

I'm interested in one set up for stock muffler, Drivability is more important to me than all out power.

Moto

I used to be a Sudco dealer when I had a small M/C repair shop in Riverside CA. I don't have the required business front to be a Sudco dealer in Michigan. I'm doing a little checking to see if there are any options available.

Carbs-R-US wasn't my intenet... otherwise I never would have posted the "secret receipe" :confused: :confused: I'm doing this as a service to our DR community and because I enjoy this type of tinkering. I was fully expecting a good portion of the people interested to tackle the job themselves... but I know there are some who don't have the tools or necessary skill set. That's the real reason I posted the ready to install, nothing else required, carb offering based on used carbs. I was also trying to provide a superior carb at a similar price to the Hessler Mikuni TM40/6 I've seen postings about. That eliminates the brand new FCR's.

I've had a number of e-mails stating that they'd gladly pay the new carb price plus my mod costs. We'll have to see how this all works out..... right now the carb I'm using works out perfectly. The new FCR's would require some more adaptation to use the stock DR push cable. :confused:

Hey, I see you are in Michigan. Get over here to GR and ride my bike while the stock muffler is still on it! :confused:

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