Jump to content
Sign in to follow this  

FCR Carb vs Needle and Jet on CV carb

Recommended Posts

Just looking for comparison of the gains: Is there about the same difference between stock drz-s stepping up to needle and jet kit with 3x3 mod as there is going from needle/jet/3x3 to fcr 39 carb? Basically wondering if you get the same bang for your buck since needle/jet/3x3 looks like about $75 and fcr carb (w/everything else needed) looks like $350 minimum. And, yeah, that includes 3x3 and jets for the fcr setup, as well.

Share this post


Link to post
Share on other sites

For that price sounds like a used FCR?

No it's not the same bang for buck, if your planning to do other mods later on the FCR will complement those mods more than the stock CV carb.

Share this post


Link to post
Share on other sites
Just looking for comparison of the gains: Is there about the same difference between stock drz-s stepping up to needle and jet kit with 3x3 mod as there is going from needle/jet/3x3 to fcr 39 carb? Basically wondering if you get the same bang for your buck since needle/jet/3x3 looks like about $75 and fcr carb (w/everything else needed) looks like $350 minimum. And, yeah, that includes 3x3 and jets for the fcr setup, as well.

Not too sure where you are going with these questions..

So you have purchased the Fcr and need to spend an extra $350..?????

You most likely only need a needle and a main jet your fcr is in good condition...nowhere near $350 ..maybe $30-$40

The 3x3 is free....Which fcr are you talking about slant body or mx??

The improvement from each type of carb is dependant on how badly the bike is running prior to re jet...

Share this post


Link to post
Share on other sites

Somewhere there is a dyno sheet that shows a properly jetted drz s at 34hp, add fcr and gain 5 at 39hp a stock s is rated at 31. so 3x3 and jets gets you 3 hp over stock jetted fcr gets you 8 over stock. Another way to look at it is $43.00 per hp for an fcr, and $25 per hp for jetting cv carb. if you are trying to max out hp just buy the fcr and get it set up now or you will wish you did down the road

Share this post


Link to post
Share on other sites

I think what HntWhtTail came up with is closest to what I was shooting for. The only difference is that I was kinda hoping for the seat of the pants feel since hp gains are usually at nearly the top revs. That was good food for thought, though, since it boils it down to $/hp. I doubt I'd do much more than the carb swap, a better air filter and drop the gearing a tad. My bike is a bone stock S, and I don't expect or need it to be much more than it is, but if noticeable gains can be had for not too much $$, why not enjoy it?

Share this post


Link to post
Share on other sites

Naked , I did the rejet and 3x3 with exhaust first , then the FCR/MX second . I can say the rejet just made the bike run better , smoother and more user friendly . The FCR/MX sort of linked the power delivery to the wrist , making the ride so much better . There wasnt any earth shattering difference in power , just better , more instant power . Although a dyno chart will say that there is an obvious HP increase It isnt a large one and is hard to notice . It is the fact that you are going from a constant velocity carb , which uses air pressure to raise the slide ( slow ) , to a flat slide carb with a pumper valve that gives the bike a neat squirt of fuel when you crack open the slide ( fast ) . It is just more of a seat of the pants thing . Just doing the 3x3 and rejetting with a good pipe ( MRD of course ) will get you a nice bike , which will run well . But if you start chasing some performance you will eventually have to go to a flat slide carb as the CV just doesnt cut it , greg

Share this post


Link to post
Share on other sites

I won't trade my fcr, but here is what you will loose with the swap. Gas mileage will go down 5 to 10 mpg (maybe 2-5 is because its more fun to drive the fcr hard). Jetting will be more finicky with elevation and temperature changes. Rear tire will wear out faster (although front tire will last longer). My experience is the stock carb is a lot easier to start (especially for the stupid), even more so when the temperature gets below 50 degrees.

Share this post


Link to post
Share on other sites

Thanks, Greg. That kind of makes me want to hold off until I can afford the fcr. Just seems like the $100 for the JD kit and Kientech screw will kind of be money down the drain since I'll probably be able to afford the carb in 6-12 mos.

And thanks, Toadl, for throwing in the 'cons'. Always good to consider. Talking about the jetting sensitivity, though, do you think it's possible to dial one in well enough to cover from 2000'-8000' elevation and about 45-95F temps without having to rejet?

Share this post


Link to post
Share on other sites
And thanks, Toadl, for throwing in the 'cons'. Always good to consider. Talking about the jetting sensitivity, though, do you think it's possible to dial one in well enough to cover from 2000'-8000' elevation and about 45-95F temps without having to rejet?

Yes. there will be a compromise in the middle. The stock carb doesn't care as much. I've seen Craigo write he changes his jetting from winter to summer. I also change my main jet from a 158 in winter to a 155 in summer (which really isn't a big change)but I live in Minnesota and ride when its in the 30's. It's supper easy to change the main jet though. theres a 17mm bolt on the bottom of the float bowl, take it off and the main jet is right there waiting to be changed. No need to remove the carb or anything else.

I also wanted to add I've had good luck with my used FCR mx. I think if you know a little about carbs its worth the risk to save half. I bought mine for under $200 bucks (good deal) plus I replaced the jets and needle.

Share this post


Link to post
Share on other sites
What's the diff between slant body and mx?

The Fcrmx is basically an upgrade of the Slant body fcr.....Both work good on the DRZ but the mx is just a little better allround in performance,as you would expect from an upgrade...

The jetting is similar in both, but modifications to carbs vary in technique..

Here is a pic of the Slant Body

590f6d2f.jpg

Pics of the Fcrmx can be found here...https://thumpertalk.com/forum/showthread.php?t=649485

Share this post


Link to post
Share on other sites
The Fcrmx is basically an upgrade of the Slant body fcr.....Both work good on the DRZ but the mx is just a little better allround in performance,as you would expect from an upgrade...

The jetting is similar in both, but modifications to carbs vary in technique..

Here is a pic of the Slant Body

590f6d2f.jpg

Pics of the Fcrmx can be found here...https://thumpertalk.com/forum/showthread.php?t=649485

Thanks, that helps a lot.

Is there a good, existing discussion thread for potential donor bikes for used fcr carbs and the mods needed to install them on DRZs?

Share this post


Link to post
Share on other sites

I put a k&n air filter with stock jetting and it runs really good. It took care of the little bog right off throttle. best of all it was cheap around 65 bucks.

Share this post


Link to post
Share on other sites
Thanks, that helps a lot.

Is there a good, existing discussion thread for potential donor bikes for used fcr carbs and the mods needed to install them on DRZs?

I remember Eddie recently said he had a used low mile fcr for sale...Send him a PM or give him a call....:smashpc:

Share this post


Link to post
Share on other sites
I put a k&n air filter with stock jetting and it runs really good. It took care of the little bog right off throttle. best of all it was cheap around 65 bucks.

According to K+N, they purposely make there filters so customers do no have to rejet. That is why I'm not a fan of there products. They purposely limit flow. As you can see on the DRZ K+N Filter, It has plastic covering the whole front of the filter.

Share this post


Link to post
Share on other sites
I remember Eddie recently said he had a used low mile fcr for sale...Send him a PM or give him a call....:smashpc:

Yeah, I saw that post, too. $350 is a little more than I have right now. That's why I put an ad in the TT classifieds to see if anyone who's upgraded from a jetted CV carb to a FCR wants to part with a used jet kit cheap. Since I originally posted this, I've read of guys going the FCR route for under $200.

As for K&N, I've seen dyno results in other applications where there was a minimal gain on top and losses in mid or low, so I'm not a fan. Also read something a long time ago indicating that their filtering was subpar, too, but don't remember where I saw that.

For now, I've decided that if I score a deal on a jet kit I'll do that and the 3x3 until I can afford the Keihin. She also needs a smaller sprocket up front for the trails, so that ought perk things up even though it won't help with the throttle woes.

Share this post


Link to post
Share on other sites

naked919 - I have a DynoJet kit if you want it. PM me your address and I'll ship it out to you. It's just taking up space right now. I would rather see someone get some use out of it. Just promise me you aren't going to turn around and sell it. When the time comes and you upgrade carbs, give the kit away to someone else that needs it.

WGW

  • Like 1

Share this post


Link to post
Share on other sites

PM sent!

Not only do I promise to re-gift it, I'll throw in any other jets I end up with to get mine dialed in. Hey, maybe if this keeps going it will end up as a complete bike in 10 or 20 years :smashpc:

Hey, I forgot to mention in the PM - shoot me your paypal info and I'll reimburse you for the shipping.

Thanks, again!

Share this post


Link to post
Share on other sites
naked919 - I have a DynoJet kit if you want it. PM me your address and I'll ship it out to you. It's just taking up space right now. I would rather see someone get some use out of it. Just promise me you aren't going to turn around and sell it. When the time comes and you upgrade carbs, give the kit away to someone else that needs it.

Got it. Thanks!

Share this post


Link to post
Share on other sites
Somewhere there is a dyno sheet that shows a properly jetted drz s at 34hp, add fcr and gain 5 at 39hp a stock s is rated at 31. so 3x3 and jets gets you 3 hp over stock jetted fcr gets you 8 over stock. Another way to look at it is $43.00 per hp for an fcr, and $25 per hp for jetting cv carb. if you are trying to max out hp just buy the fcr and get it set up now or you will wish you did down the road

That is a fantastic post and response, and thank you! I read so much about the FCR swap and this answers my questions. All my last few dirt bikes have (of course) had FCRs.

I just bought a DRZ(e) and dual sported it because I wanted to try dual sporting one more time. With years of racing dirt bikes (33), owning sport bikes, and now Harleys, I learned something many many years ago. Don't try to get a bike to more than it is capable. Don't get me wrong the DRZ I have had been jetted (and re-jetted by me), it has a Yosh pipe, and open air box, but I have a CRF450 for real aggressive dirt riding and 3 street bikes for aggressive or even cruiser type street riding. Get the bike where it performs well and call it a day. Oh, another (unsolicited) .02 cents - suspension on any motorcycle is KEY! My '10 Harley I have done ZERO to, except I have put $1000 into the suspension and probably 8 hours of my labor. Most people spend $$ on the motor to get gobs more hp & tq. Guess who gets thru to twisties and is sitting at the restaurant first?

I know not everyone is at a point in life to own many motorcycles (but you will probably get there!), but I would rather own 2 or 3 good used motorcycles designed for specific purposes than one new or newer one and try to mold it into something above what it can ultimately do.

Sorry for the ramble - age will do that to you!

Most of all Enjoy the ride!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...