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Keihin 39mm FCR-MX Install, DR650

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The Friday update: The vacuum fitting is done! After talking to a couple tuning buddies of mine the concensus was not to add a hole, no matter how small, at or near the bottom of the venturi or from the side for that matter. My fears of fuel build up in the tube was agreed with by all. I ended up with drilling out a staked brass plug in the hot start system, which is not installed on this OEM carb, and installing the stainless tube there. Even if the hot start was installed it would still not cause a system problem sharing the port. It ends up right in front of the slide cap so it's almost exactly where the BST fitting was. I'm pretty sure even the stock vacuum hose will be long enough to reach it. :thumbsup: So, tonight after work I do the install and my first road test! Pictures are coming! :thumbsup:

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It runs! :confused: I started out with all the 450 Yamaha jets... my poor engine! :confused: We were leeeeean. It still lofted the front wheel way easier than with the BST. Back to the garage and off came the carb. Every jet that came in the OEM 450 Yamaha carb is useless except the slow air and main air jets. I upped the pilot 1 step to 48 and installed an EMM needle with a 168 main. Holy snikies this thing is a buldozer. I'm so friggin pleased with this thing already and I haven't even begun to test all the jetting. The FCR seriously enhances the strength of the power band on this bike just like I was expecting. Roll-on from a dead stop will lift the front wheel right off the ground. No way would the BST allow the engine to torque down that low and pull so hard. I think the bike is pissed at me though because it seems to have ajusted it's own rev limiter down lower. :confused: Seriously though, this thing hits the limiter so fast that is seem like a two stroke with a way too big main jet. And when you shift it it just yanks you so you know you wasted acceleration in over reving the engine. The torque and roll-on are just amazing though.

So right now my initial metering point on the needle at first crack of the throttle whet from 2.75mm to 2.71mm. I'm sure I'll need to select a different needle, a little bit leaner, but my goal is to have it right in the middle or one clip lower at sea level so the boys in the clouds will have some place to go and so that it will have plenty of adjustment for those that want to run or go back to a stock muffler. I'll be selecting my final pilot to run at 2 to 2-1/2 turns out for the same reason. It will also leave plenty of play room for the guys seeking maximum fuel mileage. The main will obviously have to be changed for the stock muffler and for the guys at big elevations.

Thing (1) I don't like: The throttle return spring. Wow this thing is light! Just the weight of my hand can have the thing accelerating away. Some guys might like it but I find it a bit too easy to twist. I will check into a stiffer spring... and since I bought this carb used the PO might have installed the light spring I've seen advertised for them. I guess I'll just talk to Sudco... maybe they'll know right off what I need. Anyway, it's dinner time... jetting continues tomorrow after work! :confused:

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Based on the characteristics you describe, do you think the carb may be too small with it jumping so quickly through the range? Sounds exciting! You sure you want to go to sleep tonight?????:confused:

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Based on the characteristics you describe, do you think the carb may be too small with it jumping so quickly through the range? Sounds exciting! You sure you want to go to sleep tonight?????:confused:

No, the carb is not too small. The only way for it to run through the rpm range fast is to produce the power to get it there. Screaming top end can't happen on this motorcycle without ignition modification. The rev limiter is the limiting factor. There is no way to over come it without a custom ignition system to alter the set point. The stone relaibility of the DR would go right out the window with a modification like that. This is a grunt engine and without extensive and expensive modification it will never be anything else. This carb is perfect for this engine IMHO.

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Second jetting session Saturday: I was chomping at the bit at work today thinking of tearing into the DR to swap some jetting components. :confused: I knew the last session yesterday was on the rich side so I ripped the carb off and ditched the EMM needle and installed the EMN (no, you don't have to take the carb off to replace or adjust the needle clip, but I needed to make some push cable adjustments on the carb and cam). With the EMN I had a bit of the stock DR run-on coming down to idle so I tore the carb back off and upped the pilot from a 48 to a 50. Bingo! The 50 provided a clean and quick return to a steady idle. I noticed a bit of the wild wheelie grunt missing with the EMN on the middle clip so I raised the needle to the 4th clip position. That did it! Back to loopsville.:confused: It looks like the EMN is going to be the right needle. There is going to be plenty of adjustment for the high altitude guys. The 50 pilot is also looking like the right size. I'm at two turns out and it's running perfect without load up, surging or pulsing. This gives plenty of adjustment either way. After a few miles of testing I brought it back to the house and had my DRZ loving son "ride the big pig" :confused: He came back very impressed. Some of his comment: "Way faster with a huge torque increase" "Now you can actually thump it around tight areas without it feeling like it's going to cough and die". "It wheelies so much easier" I couldn't agree more. :confused: I'm really amazed with the somoothness and lower RPM. The FMF Q2 made a large improvement in this area but the FCR brings it to a new level. Normally the stock DR protests shifting it into 5th gear at anything less than 45-50 MPH. I was cruising through town today at 35 and 40 MPH in 5th without the bucking and protesting it used to exibit. Very cool. After enough riding and temp checks I decided to take it on the freeway. I filled it up and drove a few blocks to get to the on-ramp. I tried to maintain 70-75 MPH indicated and other than transferring from one freeway to another I stayed fairly close. I went 42.1 miles on .9 gallons for 46.8 MPG. My bike has the 14 tooth CS sprocket so the 15 and 16 tooth guys will get better mileage. There will be plenty of needle clip and pilot screw adjustment for the guys that really want to eek out the most mileage. I'll be working on the install pictures tonight and tomorrow. I plan on posting them on my web site. I'll post the link as soon as I'm done with picture editing and Power Point notations. :confused:

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"I'm really amazed with the somoothness and lower RPM. The FMF Q2 made a large improvement in this area but the FCR brings it to a new level. Normally the stock DR protests shifting it into 5th gear at anything less than 45-50 MPH. I was cruising through town today at 35 and 40 MPH in 5th without the bucking and protesting it used to exibit. Very cool. After enough riding and temp checks I decided to take it on the freeway. I filled it up and drove a few blocks to get to the on-ramp. I tried to maintain 70-75 MPH "

This sounds very interesting and worthwhile. Congrats on the hard work and research. Did you find a stronger spring to help with the quick throttle? Is the bike smoother at 75mph? 35-40mph in 5th! Now thats the way a Thumper should run! any decel popping? I'm also in MI although run the streets only and with a stock muffler....any thoughts on jetting your ebay carb for this. If you market the unit, will you offer it for bikes with stock mufflers but improved airbox?

Keep up the good work,

Motoretro

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"I'm really amazed with the somoothness and lower RPM. The FMF Q2 made a large improvement in this area but the FCR brings it to a new level. Normally the stock DR protests shifting it into 5th gear at anything less than 45-50 MPH. I was cruising through town today at 35 and 40 MPH in 5th without the bucking and protesting it used to exibit. Very cool. After enough riding and temp checks I decided to take it on the freeway. I filled it up and drove a few blocks to get to the on-ramp. I tried to maintain 70-75 MPH "

This sounds very interesting and worthwhile. Congrats on the hard work and research. Did you find a stronger spring to help with the quick throttle? Is the bike smoother at 75mph? 35-40mph in 5th! Now thats the way a Thumper should run! any decel popping? I'm also in MI although run the streets only and with a stock muffler....any thoughts on jetting your ebay carb for this. If you market the unit, will you offer it for bikes with stock mufflers but improved airbox?

Keep up the good work,

Motoretro

I have not talked with Sudco yet but my son rode it and liked the lighter spring. He thought there would be less hand fatigue on longer rides. It's not like it doesn't return to an idle.... it is just very esy to open. I didn't notice any smoother running at 75 but my BST was pretty dialed in at that speed. The lower rpm running is hands down better. I know for a fact the bike will lose some of that butter smooth low speed with the stock muffler just becuse of the big gains in this department from just going to the FMF Q2. Jetting will be posted just as I have been as I work out all the kinks. Take a ride over to the Grand Rapids area before the snow flies and I'll let you ride the King Kong Grunt Machine.... as long as you promise to bring it back! :confused:

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Nice site! That carb looks big! Is it easy to play with as far as making adjustments? Also, have you done any top speed tests? Is she faster up top?

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Nice site! That carb looks big! Is it easy to play with as far as making adjustments? Also, have you done any top speed tests? Is she faster up top?

Yes, it's bigger than the BST that's for sure. I haven't tried seeing if I could tilt the carb far enough to the right to remove the main jet access cap and get to the main. The starter wire terminal may foil that operation. :confused: I'll check it out tomorrow. The needle is very easy to get to. Tilt the carb to the left slightly. Remove two allen head cap screws to take the cap off the carb cap. Open the throttle and the slide lifts right to the top where you remove one allen head retainer nut. The needle pulls right out. Easy. Much less hassel than the BST.Of course just like the BST to change the pilot, starter or slow air jets you have to remove the carb. No top speed tests yet..... but it gets to 90 in a real hurry. :confused:

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Well this is just what I need. Some mods for the DR. Mother is getting a little cross with me modding three motorcycles at the same time. I will be watching and waiting to see how this project turns out. I would be interested in this mod but I have to be sure that the install would not be beyond my abilities. I am not very good in the wrenching department, but I have lot's of friends that are.

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Well this is just what I need. Some mods for the DR. Mother is getting a little cross with me modding three motorcycles at the same time. I will be watching and waiting to see how this project turns out. I would be interested in this mod but I have to be sure that the install would not be beyond my abilities. I am not very good in the wrenching department, but I have lot's of friends that are.

I plan on including very explicit instructions with pictures. It will list every tool you need to do the job. You can read them over and if it is still #$%&@! to you... maybe you could lure one or three of those buddies with a cold beer? :confused:

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brian why a new motor?

and rob, please come out with a complete kit! i would buy one for sure, infact if you dont, ill still pay you if you can supply me with a ready to install one for sure!!!!!!!!!!!!!!

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brian why a new motor?

My case, although patched, still has that hole in it! I want to do a built motor eventually.

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Was there any increase in top speed?

I have not tested top speed yet. I gotta find a new WFO section here in Michigan like I had out in California. I know one thing... this thing is going to pull the big 16 tooth countershaft sprocket that some of you guys use like a freight train! :confused:

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Not much of a mechanic myself, but if you come up with a full kit to just install & ride, i'll buy it. Great work Rob.:confused: :confused:

There is more information at My Web Site but this is basically it, you'll need nothing else but the stock components that attached your original BST: Right_Carb.jpg

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