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Discussion Starter · #1 ·
I bought my 750 gixxer about a year ago and have been riding it since. It has a ported head, full vance&hines supersport exhaust, k&n individuals and 1 up on the main jets. I love the power of the bike, but it has one very nagging problem. When you reach about 4,000 to 6,000 rpm it hits a flat spot and runs very rich. Once you get passed the flat spot the bike takes off and runs excellent. Would putting a stage 3 jet kit on the bike solve this problem, or should I go back to the stock header and put the airbox back on the bike?
 

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Originally posted by 92gsxr:
It has a ported head, full vance&hines supersport exhaust, k&n individuals and 1 up on the main jets. Would putting a stage 3 jet kit on the bike solve this problem, or should I go back to the stock header and put the airbox back on the bike?
<font size="2" face="Verdana, Arial">Unless the previous owner was lying about porting the head, or if the mechanic doing the jetting was a putz, you've got a motor that is as good as it is gonna get. Maybe the clips on the needles could be moved or the main jets changed. I wouldn't buy a whole jet kit though. The parts of a jet kit should be in those carbs as it is a "stage 3" set-up already.

Originally posted by 92gsxr:
I love the power of the bike, but it has one very nagging problem. When you reach about 4,000 to 6,000 rpm it hits a flat spot and runs very rich. Once you get passed the flat spot the bike takes off and runs excellent.
<font size="2" face="Verdana, Arial">How much time do you really spend in the 4-6k rpm range? Nanoseconds? I've got the same blip on mine (see below) but I think it's jetted flawlessly. And I'm using the same '92 head, 38mm carbs & K&N filters.

Maybe you should take it to a differnt Dyno and see what the run look like. Maybe you're being too picky.

 

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emulsion tubes.

09494-00677 JETL,NEEDLE(0-8 14.31 X QTY 4 = $57.24

It's one of the things that's difficult to tune out of CV carbs with no airbox anyway, that mid-range flat-spot... there is an article on factorypro's website about emulsion tube wear contributing to this. It won't eliminate the flat-spot completely, but if you've never replaced those parts, they're prolly due, and it will help you minimize the richness through the midrange that causes that flat-spot.

The other alternative is ditch the CV's and go with the RS Mikunis or FCR Keihins.
 

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Discussion Starter · #6 ·
The head was definately ported. The needles have been played with but the flat spot always occurs in the 55-70mph range. If I were to use the bike at the strip only this wouldn't be a problem, I could just dump the clutch at 8 grand and go. Do you know what size main jet comes with the stage three kit?
 

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Discussion Starter · #7 ·
Thank you both for the info. I just got done reading the article on the emulsion tube wear contributing to the flat spot. I took a look at my carbs and two of the four tubes are ovaled. I'm going to replace all four and i'll keep you posted if it helped my problem. Thanks again!!
 

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stock carbs on the oil cooled gixxers have to be the biggest pieces of shit ever assembled and sold to the general public. you'll never have anything but trouble with them and never be able to keep consistant jetting. you'll just fuck with them forever.

just my 2 cents

sell them and get flatslides
 

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I've been down this same road with some 36MM CV's that I put on my 750 with a DynoJet kit. Could never get the mid range to respond right but it was a beast at wide open throttle. I ditched those and bought some 34MM Mikuni Flatslides and have another set of problems. Can't get the sync to stay for any period of time and the throttle response is terrible. I have had the accelerator pump to both extremes trying to fix it without any success. Oh well, they look awsome anyway


 
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