carbs, which to ues, cv or flatsides?

[Rick.O]

Hi,
can anyone tell me which carbs are best to use on a race bike with a ram air, pros and cons for both would be good if anyone has any info.
Ta
Rick

[JIMBOB]

Hi my son danny buchan has only just moved in to the 400 and i have asked the same question i am told that flat slides are the way to go but you have to roll the power on because they can flood the bike very easy so i am trying to find some now if i get some i will let you know the results Jim

[zimm]

i'd go with CV's, flatslides can be tricky to setup, and even trickier to see real benefits from due to the "bogging" if the throttle is just cracked open.

they are trick though

[scooter916]

i'd go with CV's, flatslides can be tricky to setup, and even trickier to see real benefits from due to the "bogging" if the throttle is just cracked open.

they are trick though

Yup Im with Zimm on this one, my Bike was run on the Dyno with both, And to be honest the CV`s gave a better midrange and only gave up 2bhp at the very top of the powercurve, If he is a novice he will want drive therfore midrange.
Cv`s all the way, Much cheaper too

[Ballsout Racing]

On a well tuned bike they will give little extra midrange and maybe up to 2bhp more peak power. However, as previously mentioned, they can eb a real pain to set up, you'll also need patience, it doesn't always show on a dyno, and they can bog if you don't get them properly set up. The big advantage is that you have much more instant power on tap as you are controlling the slide as oposed to air pressure controlling the slide and that's what will give you a good advantage driving out of corners.

I tried them and you could feel the tyre get immediate power and feel what it was doing when twisting on the power, however, due to the 'bogging' at lower revs, I lost patience and didn't persist withe them and stuck the CVs back on which were a lot easier to use, and it didn't really do me any harm

And that is a fairly common story amongst racers that I know or heard of trying to use them. Also, I know some started highsiding as I guess they were a bit too ham fisted with the throttle

[AFM327]

I've used flatslides since I started racing my 400. At first I had problems with bogging from too much fuel at low RPM's but after tuning it I can whack it wide open above 6K and it will pull it to redline. The secret for me was custom needles, the third set was perfect, and other than changing mains to match flow changes from head work they have stayed the same. With low Hp bikes every little bit helps, especially when your not light yourself.

Craig Sanders

[Mori Man]

Sorry guy's , but the secret is to get some one who actually knows what they are doing with carb's and NOT Dyno kit's !

Here is the con

Dyno jet kits are developed and researched before sale - if you install and set-up as per instructions it will be within a few % of perfect (variance on barometric pressure from Dynojet centre) . You are being "had" getting it set-up, what you are getting is a dyno graph but from every dynokit I have seen there is one in there !

They rant on about fuelling - Dyno kit's are for full open system's if you run with baffles ect, it will be richer!

OK, that rant out the way!

FCR & TMR (+MJN's ) will out strip CVK's by a mile if set-up proper! You need a tuner who kno's how to set the accelerator pump right for your set-up.

Needles play a big part in FCR's as they are a bit more primitive than TMR's , however that doesn't stop you getting them perfect. Bogging down is usually down too to much air so you need to richen your primary circuit , as the rev's pick up and you switch to main and more fuel is kicked in ; it then shifts like a rocket. Well set-up you'll get around 6-8 BHP gain and NO throttle lag!

I have TMR's on the ZRX and went back to CVK's and could write a postcard between opening the throttle and response compared to the TMR's

Just fitted FCR's on the ZRX H2 and not even set-up i could crack the throttle and it picked up (under load that might be different).

Another point, did the factory SP's "bog" with full throttle?

Soory, but you just aren't finding some one who actually know's what they are doing and BTW I ain't one of them but learning

DS

[Ballsout Racing]

Soory, but you just aren't finding some one who actually know's what they are doing and BTW I ain't one of them but learning

DS

Actually, I use one of the best ZXR400 tuners in the country. FACT: you will not get another 6-8bhp by just bolting on FCR's however well set up they are, on a top tuned race engine . That would be giving me up to 87bhp!mmm, now there's a thought, if only it was that easy . As I said, I've been down that route, they gave no more than 2bhp top end. Now, I'm not saying they don't give a nice advantage, but you do have to adapt the way you put the throttle on to get the most out of them. And I beleive only an extremely good racer would gain anything on track from them over CV's.

The same people have fitted an injection system to a race ZXR400 with a custom tunable map, and even then they only got less than a 2bhp gain

[Mori Man]

OK, i wasn't talking an already race tuned engine as the engine work will bring out the best.

But, if CVK's are the better deal why was the SP and F3 kitted with FCR's ?

Indeed most non fuel injected racers I see run FCR or TMR carb's (CR's on older bikes) - sorry but CVK's are no where near in the same league!

[Ballsout Racing]

OK, i wasn't talking an already race tuned engine as the engine work will bring out the best.

But, if CVK's are the better deal why was the SP and F3 kitted with FCR's ?

Indeed most non fuel injected racers I see run FCR or TMR carb's (CR's on older bikes) - sorry but CVK's are no where near in the same league!

I really can't comment on other bikes as I don't know. I'm sure FCR will give different advantages on different bikes. Also how well have these other bikes been developed? I mean if they haven't then maybe an immediate good gain can be had by just fitting them!

FCR's obviously work well on a standard ZXR400, but how much extra power do you get on an SP over a standard CV carbed bike, bearing in mind the SP also has better cams and ignition as well? Is it 7-8bhp? My guess is less. But I bet the SP feels faster just due to the fact the way FCR's work. Just my opinion.

This is a racing forum so my previous posts have been based on my racing experiences with FCR's on a ZXR400 and can only be taken as such, although I would hope that people would take all opinion into consideration, as I do, and then make their my own mind, as I did. (and not to mention the huge cost of buying and trying the FCR's for them to be currently sat on my shelf - not for sale BTW, I may try them again! )

[Mori Man]

(and not to mention the huge cost of buying and trying the FCR's for them to be currently sat on my shelf - not for sale BTW, I may try them again! )

LOL

Tell you what - seeing as you do race and if you want some sponsorship next year and i want to try them........


Bito R&D (That's the MotoGP Bito) make specific FCR's

I have 32mm in just now and will do a power check on them.

The Bito's are 33mm and will swap over and get set-up (if needed) and power check.

I see a gain, I will send to you - you try and like then buy otherwise send them back,

If you buy i will do a reduce cost for "space" on your bike for my logo - how does that sound?

BUT , we need this independently verified as i am putting my name on the line here - very easy for you to say they are kack and still keep.

Open too suggestions but willing to do something

[Ballsout Racing]

I very much appreciate the offer , it's not often one gets them.

However, this year I've taken a sabbatical, and I'm not sure if/what I'll be doing next year, but at the moment I'm pretty sure I won't be doing a full season on the ZXR. Just may take it out for a bit of fun at a few rounds. So, as such, I won't want to be spending a lot of time or money trying to get my bike back up to championship winning potential, because it'll be me that needs the help

Thanks for the offer, but I think it's only fair to decline at this time. Thanks again.

Greville

[jake]

Sorry guy's , but the secret is to get some one who actually knows what they are doing with carb's and NOT Dyno kit's !

Here is the con

Dyno jet kits are developed and researched before sale - if you install and set-up as per instructions it will be within a few % of perfect (variance on barometric pressure from Dynojet centre) . You are being "had" getting it set-up, what you are getting is a dyno graph but from every dynokit I have seen there is one in there !

They rant on about fuelling - Dyno kit's are for full open system's if you run with baffles ect, it will be richer!

OK, that rant out the way!

FCR & TMR (+MJN's ) will out strip CVK's by a mile if set-up proper! You need a tuner who kno's how to set the accelerator pump right for your set-up.

Needles play a big part in FCR's as they are a bit more primitive than TMR's , however that doesn't stop you getting them perfect. Bogging down is usually down too to much air so you need to richen your primary circuit , as the rev's pick up and you switch to main and more fuel is kicked in ; it then shifts like a rocket. Well set-up you'll get around 6-8 BHP gain and NO throttle lag!

I have TMR's on the ZRX and went back to CVK's and could write a postcard between opening the throttle and response compared to the TMR's

Just fitted FCR's on the ZRX H2 and not even set-up i could crack the throttle and it picked up (under load that might be different).

Another point, did the factory SP's "bog" with full throttle?

Soory, but you just aren't finding some one who actually know's what they are doing and BTW I ain't one of them but learning

DS

So did you win them fcrs then dude? and have you decided to keep them

[Mori Man]

So did you win them fcrs then dude? and have you decided to keep them

Got my 32mm a while back, it was 33's I was bidding on for you - they went crazy price right at the end

Still keeping an eye open though.

[robracer]

With Flatslide Carbs you will loose quite allot of midrange, & you will find (if racing)the bike really does not make power until you hit 9-10K revs but CV's will be more linear on the power curve. To ride 2 ZXR's one with & one without this is the most noticeable difference.