How far will my gas mileage drop w/ V&H full exhaust and jets?

[Gandalf]

I have a 1990 Katana 750 that performance-wise is completely stock. I'm looking for a bit more performance (along with a bit of a better-sounding growl) so the stock pipes gotta go. I'm currently getting about 38mpg city and 43 highway...how will that change if I swap out the exhaust and jets? I'm looking at a Vance and Hine's full exhaust, and either a stage 1 or 2 jet kit. (Not sure what kit I'll go with...Ivan's is supposed to be nice but its pricey.)

I'm kinda looking for specific numbers for the stage 1 and/or 2 from people who've done it...I'd rather keep my highway mileage at at least 35 mpg.

On an unrelated topic, a friend of mine was talking about getting a hypercharged for his vstar, and we were wondering if they even make one for the katana, and if that would be a viable option at some point. (Googling it didn't turn up anything either way.)

[05RedKat600]

That depends entirely on YOU and your right hand, not so much on the mods. If you are easy on it, you may see it increase. If the pipe makes you go WHOOOOOO!!!! it's gonna go down.

[Gandalf]

Haha how about assuming roughly the same amount of lead foot syndrome? I mean bigger jets = more gas so I'm assuming regardless of my driving it's gonna go down, since I'm burning more fuel even while I'm just cruising. But am I likely to be looking at 2-3 mpg, or 5-10? Or somewhere in between? And how drastic is the difference between a stage 1 and stage 2 jet kit, both in terms of fuel efficiency and power increase?

(This is my second bike - my first was an fzr600, which I never really modified, just maintained and repaired. Most of my knowledge is car-related, so bear with me please)

[arsenic]

I have a 1990 Katana 750 that performance-wise is completely stock. I'm looking for a bit more performance (along with a bit of a better-sounding growl) so the stock pipes gotta go. I'm currently getting about 38mpg city and 43 highway...how will that change if I swap out the exhaust and jets? I'm looking at a Vance and Hine's full exhaust, and either a stage 1 or 2 jet kit. (Not sure what kit I'll go with...Ivan's is supposed to be nice but its pricey.)

I'm kinda looking for specific numbers for the stage 1 and/or 2 from people who've done it...I'd rather keep my highway mileage at at least 35 mpg.

On an unrelated topic, a friend of mine was talking about getting a hypercharged for his vstar, and we were wondering if they even make one for the katana, and if that would be a viable option at some point. (Googling it didn't turn up anything either way.)

There's no such thing as a stage 2 jet kit for a Katana. Ivan only makes jet kits for a 98-06 Katana. You should go with a Factory Pro stage 1 jet kit. There is no such thing as a "hypercharged".

[Gandalf]

Oh, ok - that makes my choices easy. ;p But I'm still wondering about the gas mileage effects. (I drive about 300 miles a week - student working full-time - so gas mileage is a concern lol).

and here's a hypercharger: http://www.cruisercustomizing.com/ku...0/part/KY-9423

[arsenic]

and here's a hypercharger: http://www.cruisercustomizing.com/ku...0/part/KY-9423

That's got to be a Harley invention there.

[05RedKat600]

Oh, ok - that makes my choices easy. ;p But I'm still wondering about the gas mileage effects. (I drive about 300 miles a week - student working full-time - so gas mileage is a concern lol).

and here's a hypercharger: http://www.cruisercustomizing.com/ku...0/part/KY-9423

That's a pretty fancy name for jets, an air scoop, and a hi flow filter. Nothing magical there. Those Harley guys will buy ANYTHING if it's chrome.

There is nothing like that for the Kats. Keep the stock airbox AND filter if you know what's good for your mental sanity.

Again, provided you don't hot rod it, you may actually see mileage increase. Realistically, it will probably stay the same. However, I will almost guarantee you will ride it harder. It's a human mentality psychological thing.

From what I understand you shouldn't need to change the jets out, just the slide needles. They are a completely different shape from the factory needles.

[Gandalf]

Alright, sounds good. Thanks. And yeah I know what you mean - it was the same way when I boosted my Regal to 14.5 PSI - should've improved gas mileage but it was just too much fun! (In the words of jeremy clarkson, "More powerrrr!")

And do the slide needles come in the factory pro kit arsenic mentioned?

[Kreylyn]

Okay, to clear something up...

Bigger jets does not automatically = much more fuel usage.

Your bike has an optimum air/fuel ratio. That doesn't change. What a jetkit does with bigger jets and adjustable needles is give you much more control over that a/f mix for the entire rpm range. OEM jets and needles tend to have certain rpm ranges that are lean, or at the least have a variable a/f ratio through out the rpm ranges.

So it's not all about pumping alot more gas at it... it's about smoothing out the a/f mix all the way around and making the engine perform more to it's potential.

Generally speaking, the actual mpg would have little change unless you started way off to begin with. Some do...

Krey

[arsenic]

I mean bigger jets = more gas

Factory Pro doesn't use larger jets. They use the stock size and include a set that is one size up. You need to figure out which size works best for you by testing both. Pick the jet that pulls the best at wide open throttle.

And do the slide needles come in the factory pro kit arsenic mentioned?

That's kinda what a jet kit is

[Gandalf]

Okay, to clear something up...

Bigger jets does not automatically = much more fuel usage.

Your bike has an optimum air/fuel ratio. That doesn't change. What a jetkit does with bigger jets and adjustable needles is give you much more control over that a/f mix for the entire rpm range. OEM jets and needles tend to have certain rpm ranges that are lean, or at the least have a variable a/f ratio through out the rpm ranges.

So it's not all about pumping alot more gas at it... it's about smoothing out the a/f mix all the way around and making the engine perform more to it's potential.

Generally speaking, the actual mpg would have little change unless you started way off to begin with. Some do...

Krey

Aha, that makes sense. Btw does anyone have a link to the factory pro kit? motorcycle superstore and revzilla don't seem to carry it, and googling it all I'm finding are the stage 3's.

[arsenic]

89-97 Suzuki GSX750F Katana Factory Pro Jet Kit 1.0

[Psycho1]

Another thing to consider if you want more performance and don't mind giving up a little top speed would be to go a few teeth larger on the rear sprocket, or 1 tooth smaller up front (or both). This would give you the biggest seat of the pants performance gain, and would allow the engine to work much easier, requiring less throttle input to get the same results. Your mileage may improve under most riding conditions (other than when banging the redline WOT).

[DClark]

And do the slide needles come in the factory pro kit arsenic mentioned?

90% of the magic in a jet kit is the needles, they have a special contour and are adjustable. Instructions and the main jets are included, but you can get info for free and main jets are are cheap. Try to buy just needles from a jet company and they'll laugh at you.
On my 1100, peak highway mpg dropped from 42 to 38mpg. Can't say it was all due to the jet kit/4-1 combo as stations switched from gas to e10 during that time.
However, I would expect you see a drop of a mile or so with the combo. The reason is that it will give you a richer mixture, richer= more fuel spent. Your bike won't run rich, it will run properly. Stock, it is so lean as to have lean spots and all the driveability problems associated with that. Adding the combo will make your bike more responsive and although the dyno won't show a huge jump in power, it will feel more powerful simply because it runs like it should. I still remember what my 1100 felt like when it had stock CA spec jetting and stock pipe, ran like crap, terrible response and when driven in below freezing weather, had to keep the choke on for at least 5 minutes as it was as cold blooded as a dead lizard!