Need some Jetting INFO**

[tampaFZR600]

Hey guys.
Not sure how accurate it is, but the theory seams sound.

Awesome man, that helps a lot.

But what about the little notches on the needle? Do I need to change that up at all?

[aero540t]

Hey guys I have another question regarding jetting. I'm getting horrible gas mileage (considering only K&N filter and SS2R slip-on) of about 32MPG on the highway. Also whenever I get in the higher rev range I get black smoke shooting out of the muffler so obviously I'm running really rich.
I have a Dynojet stage 1 jet kit with 118 mains, 52.5 starter, and A/F screws turned out 3 turns. My emulsion tubes look fine, I checked them this winter when I rebuilt the carbs.
I think I'm just going to put in 112 mains from Dynojet and see if that's all it is...does that sound right?
Possible issues: my airbox needs to be actually put on the carbs, it's just resting on top till I get the rubber boots softened up. Also my carb to motor boots are cracked and I'm replacing them soon.
That should also hopefully fix my rough idle.
Otherwise the bike revs fine and sounds great besides a rough idle and running very rich.

[yamaha_george]

Hey guys.
Not sure how accurate it is, but the theory seams sound.

Awesome man, that helps a lot.

But what about the little notches on the needle? Do I need to change that up at all?

TFZR600
NO one knows that until YOU do the throttle position check !


Aero, Get the boots fixed first then and only then will you have a set up that you can test and work out what Jets need altering

[dru86]

George,
The tape trick is NOT how you tune cv carbs, most of the jetting/metering (eg Main Jets, needle position and float level) is sorted out using full throttle, then the other stages such as Idle and to some extend cruising are metered by the fuel screws .
Read factorypros website here

I used a gas analysis while tuning the bike with the above order of sequence and have achieved very good acceleration from 2000rpm to redline and good fuel economy.

These pictures also explain how each component affects fuelling at each rpm. As can be seen changing the main jet size changes the metering over the whole range but more so at the top, that's why the correct main must be selected first!

[yamaha_george]

George,
The tape trick is NOT how you tune cv carbs, most of the jetting/metering (eg Main Jets, needle position and float level) is sorted out using full throttle, then the other stages such as Idle and to some extend cruising are metered by the fuel screws .
Read factorypros website here

Dru86,
I do not remember EVER saying that the main jet is EXCLUSIVLY the area for WFO, the charts mearly show what acts where in an APPROX rev range (since every engine is different)
Since the throttle actually operates the carbs its position at what rev range defines what area you should look at in the overall relationship.

When I want tech advice I never ever listen to someone trying to sell me something, the guy who showed me was not only a racer but a tuner also and since he helped the likes of Kenny Roberts I think he has my attention.

I have followed that advice for 30+ plus years I bought my first & second west indian houses and my estate with the winnings from street dragging and the guys from Venemoto (Yamaha South America ) regularly rode my bikes when they came over to visit my service shop on their refresher courses for my staff and I. The only complaint I ever had was on a SECA 750 that the throttle response was "sluggish" and the tuning tip to over come that was given by a prominent race tuner with Venemoto and I passed on here a couple of months ago.

[dru86]

George,
The tape trick is NOT how you tune cv carbs, most of the jetting/metering (eg Main Jets, needle position and float level) is sorted out using full throttle, then the other stages such as Idle and to some extend cruising are metered by the fuel screws .
Read factorypros website here

Dru86,
I do not remember EVER saying that the main jet is EXCLUSIVLY the area for WFO, the charts mearly show what acts where in an APPROX rev range (since every engine is different)
Since the throttle actually operates the carbs its position at what rev range defines what area you should look at in the overall relationship.

When I want tech advice I never ever listen to someone trying to sell me something, the guy who showed me was not only a racer but a tuner also and since he helped the likes of Kenny Roberts I think he has my attention.

I have followed that advice for 30+ plus years I bought my first & second west indian houses and my estate with the winnings from street dragging and the guys from Venemoto (Yamaha South America ) regularly rode my bikes when they came over to visit my service shop on their refresher courses for my staff and I. The only complaint I ever had was on a SECA 750 that the throttle response was "sluggish" and the tuning tip to over come that was given by a prominent race tuner with Venemoto and I passed on here a couple of months ago.

George,
you've COMPLETELY MISREAD WHAT I HAVE WRITTEN. Nowhere did i say that you said that the main jet is EXCLUSIVELY the area for WFO, please reread what I have written. The steps that carbs are tuned are explained very well in that sheet that I scanned.

FIRST: the correct main jet is selected by FULL throttle so that the bike pulls cleanly from 7-8k to redline.
SECOND: The needle jet is positioned so that the bike pulls, again on FULL throttle, from 4k to 7ish
THIRD: The float height is set so that the bike pulls FULL throttle from 2k to 4k, float height also affects cruising however.
FORTH: The fuel screws are set to achieve best PART throttle cruising and idle.

The whole reason factory pro give that advice on there site is so that people can tune their carbs correctly, they're not going to sell many jet kits if they don't have any support for their product.

I don't really care what some tech has told you about tuning carbs on some old seca750. What experience have YOU had in tuning CV carbs on a fzr? I've tuned at at least 5 different sets of carbs on both 400s, 600s and my 660 in various stages of tune from stock to slipons, full systems, K&Ns, pods and modified airboxes and have had my combinations checked while using 02 sensors on the street and by having time done on the dyno.

[yamaha_george]

George,
The tape trick is NOT how you tune cv carbs, most of the jetting/metering (eg Main Jets, needle position and float level) is sorted out using full throttle, then the other stages such as Idle and to some extend cruising are metered by the fuel screws .
Read factorypros website here

Dru86,
I do not remember EVER saying that the main jet is EXCLUSIVLY the area for WFO, the charts mearly show what acts where in an APPROX rev range (since every engine is different)
Since the throttle actually operates the carbs its position at what rev range defines what area you should look at in the overall relationship.

When I want tech advice I never ever listen to someone trying to sell me something, the guy who showed me was not only a racer but a tuner also and since he helped the likes of Kenny Roberts I think he has my attention.

I have followed that advice for 30+ plus years I bought my first & second west indian houses and my estate with the winnings from street dragging and the guys from Venemoto (Yamaha South America ) regularly rode my bikes when they came over to visit my service shop on their refresher courses for my staff and I. The only complaint I ever had was on a SECA 750 that the throttle response was "sluggish" and the tuning tip to over come that was given by a prominent race tuner with Venemoto and I passed on here a couple of months ago.

George,
you've COMPLETELY MISREAD WHAT I HAVE WRITTEN. Nowhere did i say that you said that the main jet is EXCLUSIVELY the area for WFO, please reread what I have written. The steps that carbs are tuned are explained very well in that sheet that I scanned.

FIRST: the correct main jet is selected by FULL throttle so that the bike pulls cleanly from 7-8k to redline.
SECOND: The needle jet is positioned so that the bike pulls, again on FULL throttle, from 4k to 7ish
THIRD: The float height is set so that the bike pulls FULL throttle from 2k to 4k, float height also affects cruising however.
FORTH: The fuel screws are set to achieve best PART throttle cruising and idle.

The whole reason factory pro give that advice on there site is so that people can tune their carbs correctly, they're not going to sell many jet kits if they don't have any support for their product.

I don't really care what some tech has told you about tuning carbs on some old seca750. What experience have YOU had in tuning CV carbs on a fzr? I've tuned at at least 5 different sets of carbs on both 400s, 600s and my 660 in various stages of tune from stock to slipons, full systems, K&Ns, pods and modified airboxes and have had my combinations checked while using 02 sensors on the street and by having time done on the dyno.

I am not going to get into a pissing match with you but the facts are that my teacher is a name in the race tuning world and that I did my tuning as a Yamaha tech agent so 4-5 bikes pales a little.

You go your way I will go mine what anybody else decides to do so be it they are all their own men.

My advice is for free and as such is worthless..............

[reelrazor]

I'ma toss my two cents in here, having plenty of plenty experience with direct pull slide carbs AND with CV carbs. I am a firm believer in making a throttle indicator as George said, I do it on every sled I tune...I've also done it on all my (and others') RD/RZs that I have tuned. I've done it on the old GSXR endurance bike I have been involved with-but IT, and all the others I have throttle taped have carbs, whose slides are actually the throttle valve .

With CV carbs, throttle position does not have a linear relationship with the slide.

50% throttle input on a flat road in third gear may likely result in the slides running 1/4 open. In sixth, 50% throttle with waaay more wind load, it's gonna be more like 2/3 slide open.

Point being, CV carbs are vacuum (and therefore 'load') dependent. A 'move' in throttle position will result in a an initial large slide opening which will then decrease.