Jump to content
Sign in to follow this  

Help deciding / understanding carb choices

Recommended Posts

To tell a novel in a paragraph i'm currently in the process of swapping an 02ktm520EXC for a drz400s model. The Ktm is an amazingly fun bike to ride but i bought it used and have had seemingly excessive amounts of problems with the bike preventing me from riding. I currently ride twice a week and do alot of dualsport riding. Everyone i ride with other than the exception of one other guy rides a drz400s and they never have hardly any problems. My only reasoon for sacrificing the power and light weight of the ktm is the exchange of reliability which leads me to my question(S).

I've read alot about the FCR 39mm carb swap and i am wandering a few things from those of you who have had experience with this mod.

1. Is a 10%/ 4hp gain worth 600 dollars?

2. Is there anything wrong with purchasing a used one off ebay for half the price?

3. What does a 10% hp gain feel like from the seat? can you power up a wheelie? can you crisply bring the front wheel up with a twist of the throttle? Just some sort of explanation of the felt difference after installing the 39mm.

4. If i were to purchase this i would probably also have an aftermarket pipe. does a slip on silencer effectively work with the new carb or do i have to buy the full header and silencer and would this effectively increase power?

5. and lastly, The guys i ride with aren't mechanics and they have done nothing more to their bikes than swap the seat and bars out. Is that why there bikes are so reliable? Would this carburetor make the bike less reliable and user friendly. I don't want to have to worry about having problems out on the trails and my main reason for buying a drz is its ability to stay out of the garage and always be ready.

Thanks in advance for the help and advice. I realize that's alot to read but any info will help and i appreciate it.

Share this post


Link to post
Share on other sites

I also meant to ask about the smooth operating drz motor and the smooth feel of the bike entirely. does the new carb have any effect on that?

Share this post


Link to post
Share on other sites

If it's mostly used as a trail bike I would just do the 3x3, re-jet stock carb and pipe.

Share this post


Link to post
Share on other sites

1) Thats up to you. You could try the 3x3 and rejet for $75 bucks.

2 ) Huge problems search ebay fcrs. I would spend the coin on a legit one from TT or Eddie at Epic.

3) Its much better throttle responce so it lifts the front end easier.

4) You should have a full system (yosh ti and mrd pro are for the most hp but you will lose the tq down low with both of these)

5) No if you stick with proven setups the bike will still run spot on.

Share this post


Link to post
Share on other sites

I agree with DRZ streetfighter. But I don't like loud bikes, I would go with the JD jet kit for the CV carb- , E-cams and E exhaust (same can pretty much but bigger header). It's pretty easy mods and gives some increase yet fairly inexpensive. I'd buy a used carb only if I had a chance to run it first and with E-bay you can't do that.

Share this post


Link to post
Share on other sites

thanks for the responses guys. Great to know the reliability stands true even modified.

- So why 3x3 rejet rather than the FCR due to trail riding. I ride about 70/30 (70% trail/off road/logging roads, 30% road to get the trails and back.)

- Are there pipes that increase low end grunt rather than top end hp?

- what about the smooth operating feel of the drz from the factory? Do carb / exhaust mods affect this?

Share this post


Link to post
Share on other sites

Also ill have to admit i like loud pipes as long as they have an acceptable tone. Im a large believer in loud pipes save lives but they have to sound good. Outside of that debate, the reason for the pipe is more power, as with the carb, but i dont want to lose any bottom end

Share this post


Link to post
Share on other sites

2006 S, FCR MX, stock cams, E head pipe, 3x3, geared at 14/49 for tight single track, 14/44 for fire roads and two track. There is a noticable difference with the stock vs FCR carb, maybe not as great power wise but certaily a large improvement with throttle response. On the trail I would notice a lag when I turned the throttle with the stock carb and I found myself trying to anticipate when I wanted to have the power by opening it slightly before I normally would have. Now with the FCR the power is on "right now" and does pull harder. With the FCR and the 14/49 gearing lofting the front wheel isn't much of a problem.

Is it worth the cost? That's up to you. If you are just putting around on the trail with a few buddies and the trail isn't very challenging you probably won't need it but I'm trying to keep up with buddies on dedicated 250 and 450 size woods bikes and the FCR made a good difference. Fitting the FCR and having the suspension redone for my weight are the best two mods I've made.

Edited by npm

Share this post


Link to post
Share on other sites

Im going to have to interrupt this and just say that this is an incredibly helpful site as i have been a member to many forums and very few are they as organized and operational as this one.

now back to business,

- npm, your description seems to be what i'm looking for here. to those of you who took the route of the 3x3 rejet how would you describe it in comparison to npm's FCR description

Share this post


Link to post
Share on other sites

It ran better and smoother with the jet kit, my mileage did not suffer, I can pull a wheelie easier in first with throttle alone or by banging 2nd gear shift or popping the clutch after I'm in 2nd. That is with 15/41 gearing, 18/21 rims on TrailWings. But yes with or without the jet kit, I kinda gotta anticipate the logs arrival in order to time the loft of the front tire to get over it.

Share this post


Link to post
Share on other sites

Just to be clear I did do the 3x3 and rejet the stock carb prior to getting the FCR and was happy for a while with just that mod. The accelerator pump on the FCR makes the initial lunge much more right now when compared to the 3x3 and jetted Mikuni. I got mine from Eddie as he will jet them for your application and do the wiring mod on the acc pump so it truly is a "bolt and go" installation.

Share this post


Link to post
Share on other sites

many of us tried the re-jet of the cv and then opted for the fcr.

it costs more that way. decide what you want from the bike & what you are willing to invest in it money wise & make your carb choice based on that.

if you want it to be all it can be and don't mind throwing $ at it - go fcr now.

if you just need a little more performance & don't want to throw $ at it - re-jet the mikuni.

Share this post


Link to post
Share on other sites

alright so i broke down and decided to get the jd jet kit and do the 3x3 mod and get a full yoshi. Now after watching the instructional video i decided im absolutely more than capable of doing the 3x3 mod but i'm just not that comfortable doing the jetting. I'm not a mechanic but i like to have a general understanding of what the mechanic is doing, and would rather not pay him to drill a hole. so i'm going to have the local shop do the jetting and was planning on doing the cutting after i get it back. Is that a bad idea to do it after considering the air flow and the fuel mixture with the larger hole in the airbox?

Share this post


Link to post
Share on other sites

A fromer KTM520 owner that is not a mechanic, hmmmm, I can see the problem.

If the shop that installs the jet kit will test ride or dyno the bike, the air box should be modified to be compatable with the new jetting. So, I would mod the air box first. If the shop will not be testing the bike, you can mod the air box later but you will be on your own for final testing and tuning.

Share this post


Link to post
Share on other sites

A fromer KTM520 owner that is not a mechanic, hmmmm, I can see the problem.

If the shop that installs the jet kit will test ride or dyno the bike, the air box should be modified to be compatable with the new jetting. So, I would mod the air box first. If the shop will not be testing the bike, you can mod the air box later but you will be on your own for final testing and tuning.

Ok so when you say final tuning you just mean adjusting the fuel mixture screw correct? and the carb stays in its resting place on the bike when this is done?

Share this post


Link to post
Share on other sites

go with the fcr my 02 E model came with one, my buddies 07 E model did not.His bike is a dissappointment to ride after ridding mine.

Share this post


Link to post
Share on other sites

A fromer KTM520 owner that is not a mechanic, hmmmm, I can see the problem.

If the shop that installs the jet kit will test ride or dyno the bike, the air box should be modified to be compatable with the new jetting. So, I would mod the air box first. If the shop will not be testing the bike, you can mod the air box later but you will be on your own for final testing and tuning.

The shop is also kind of low end, no dyno etc.

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...