03 FZ1 Mods

rwaldojr

rwaldojr

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I have been thinking about doing the stage one jet from holeshot.com. I am nervse because if the job is not done right your gas milage is shot and the performance will go down. I cannot do it because I do not have any experience with carbs or any engines on a motorcyce. Anyone think it will make a big difference or should i just go for the stage 2 or just leave it alone.
 
If gas milage is important to you....

I would leave the carbs alone!!!:noworries:

I'm getting 43 mpg with my '03 FZ1. I have all of the performance I can use on the street, and great MPG's. It's the best of both worlds. :sport12:


Earl
 
Mpg

You must understand that the very nature of your proposed modifications are counterproductive as far as miles per gallon go. The reason for the carb modification is two-fold.

The way the factory reduced emissions in most of the last decades crop of motorcycles was to use 'small' jets. This accomplished one of two things, #1It reduced the volume of gas passing through the intake tract, ie. (through the carb, down through the intake manifold, through the cylinderhead port, and into the combustion chamber of the head), also raw air was introduced into the combustion process by what most refer to as smog pumps, ie. AIS into the ehaust tract, to provide a more complete burn of the intake charge. By reducing the fuel gas ratio, less polutants came out the exhaust pipe..........#2 And less fuel equaled better gas mileage.

But this had a negative effect of sorts, a pluss and unavoidable minus as it were. With less fuel and more air, it burned at higher temperatures inside the combustion chamber of the head, which could lead to pre-ignition, or 'pinging'. The design of the five valve head however, overcame this propensity to ping, and additionally allowed higher compression ratios which typically tend to cause pinging in two and some four valve heads. but the pluss end of this was increased mileage per gallon...........but neutered horspower, due to the smaller combustion charges of fuel introduced into the combustion chamber.

Small combustion charge = small horspower, Large combustion charge = large horspower.

So the final outcome of this design was a motor that ran hotter due to running 'lean' and less potential horspower.

The quickest cure/mod, was to fatten up the jets, ( bigger jet orifaces). Again more fuel present in the combustion chamber, more power,........additionally the incoming charge which was larger in volume and the fuells cooler charge due to its larger volume, helped the motor to run cooler. But the downside for emissions was that more burnt/unburnt fuel equaled more emissions out the exhaust pipe, equaled higher polutant readings

I know this is becoming a history lesson and drawn out, BUT... to understand the process it was nessessary. When you change the jets, you increase available horspower, but more fuel goes through the system per every revolution. Additionally an aftermarket exhaust is designed to flow more burnt gasses than a stock system, again more volume of fuel and evacuated burnt gasses through the motor, - less miles per gallon, + more horsepower.

Rejetting will smooth out all the throttle openings/settings as you twist the throttle open and will reduce or stop altogather the deceleration "popping", and will smooth out any throttle aplication.

So ultimatly persueing these mods will make your fuel consumption increase per mile= Less MPG. There is however one way to recoup some of the lost mileage per gallon, and thats through higher gearing, but thats oftentimes doesn't bring back all the differences in the additional fuel consumption. About all you can do is be happy with 40 mpg modified(possably less) or be happy with your current mpg, of around 45 ish.
 
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