1996 ZX-7R carb issue

[IceZX7R]

I have a 1996 ZX-7R with a full Muzzy exhaust. Bike has about 4500 miles on it. I'm not sure if it has a jet kit or not and it has the stock air cleaner.

When I'm at about 2500-3500 rpm and hit the throttle hard it sputters / hesitates before it will kick in. If I ease the throttle open it's fine. If I'm over 4000 rpm it doesn't have this issue. It also only seems to happen in 2 or 3rd gear not 1st. If I'm past 4000 rpm I can go through the gears full throttle no prob and runs fine.

I'm not sure if it's a jetting issue or a fuel/air issue.

I'm thinking about putting a set of Keihin 41mm flats on it soon but would like to have it running good before I do that.

[maggioracing]

if you plan on putting some fcr 41's you'll have a hard time getting the bottom end dailed in b/c of it's size and no high compression to feed. You're in race stats territory with those things.
As far as the jetting. I believe if you go to dynojet.com and look up the instructions for their zx7r stage one, you'll see the small fine print that states under 4,000 rpm (something like that) this will feel worse with the jetkit installed. Basically as hyou already may now, the 7r does not make awesome power under 5000-6000 rpm and a jetski may increase the mid and top but the bottom suffers.
anyway read the directions and it will show you what areas have to be drilled. it the carbs are drilled in these areas, it's been jetted.
why are you in second and third gear with the rpm so low? the higher the next gear is, the higher the rpm will have to be to catch that particular gear...I mean when you blip the throttle. some sort of ratio/gear/rpm thing.
-Frank

[IceZX7R]

Originally Posted by maggioracing

if you plan on putting some fcr 41's you'll have a hard time getting the bottom end dailed in b/c of it's size and no high compression to feed. You're in race stats territory with those things.
As far as the jetting. I believe if you go to dynojet.com and look up the instructions for their zx7r stage one, you'll see the small fine print that states under 4,000 rpm (something like that) this will feel worse with the jetkit installed. Basically as hyou already may now, the 7r does not make awesome power under 5000-6000 rpm and a jetski may increase the mid and top but the bottom suffers.
anyway read the directions and it will show you what areas have to be drilled. it the carbs are drilled in these areas, it's been jetted.
why are you in second and third gear with the rpm so low? the higher the next gear is, the higher the rpm will have to be to catch that particular gear...I mean when you blip the throttle. some sort of ratio/gear/rpm thing.
-Frank

Hi Frank... thank for the response.

Would 39's be better to go with on the street for the FCR's?

Also I was off on the rpm. I shift from 1st to 2nd and if I let the rpm's drop to 4500-5000 then hit the throttle again it acts like I have to switch to reserve... not 2500-3000 rpm as I stated before.

I will check out the dynojet site and then check the carbs to see if there is a jet kit installed.

As far as I know it has stock gearing. I just picked the bike up about a month ago. Paid $2200 and it only has 4500 miles on it.

[IceZX7R]

btw maggio I have seen some of your youtube vids and other pics of what you have done to your bike... pretty sick stuff man! Nice work

[davewaibel]

There is no hp gain to be had with the FCR's- 0 hp- and if you think your carbs are finicky now, I have news for you- I have three bikes, two of them have FCR, with the exception of the symphony of flateslides, rattling, there is now viable reason to put them on 96-03 zx7's. especially 41's, 39's are not that much better- good luck though if you wish to take on this project-I like mine, but you can easily flood yourself to the side of the road.

[IceZX7R]

Originally Posted by davewaibel

There is no hp gain to be had with the FCR's- 0 hp- and if you think your carbs are finicky now, I have news for you- I have three bikes, two of them have FCR, with the exception of the symphony of flateslides, rattling, there is now viable reason to put them on 96-03 zx7's. especially 41's, 39's are not that much better- good luck though if you wish to take on this project-I like mine, but you can easily flood yourself to the side of the road.

I had a set of Keihin FCR's with a 1/4 turn throttle on my old 89 ZX-7. I added those after the Muzzy exhaust. Took about 2 months to dial in the carbs but after that it was insane. Huge difference in power. I also ran velocity stacks with custom filters and no air-box.

My question to you is if they add 0 hp and are a pain, why do you have them on 2 out of 3 of your bikes?

[maggioracing]

I guess I can answer it for him. For the same reason I ran bigger carbs on my sea doo. Stock were 38mm, I jumped to buckshot BRM 47's. TOO BIG A CARB ,and was a bitch to tune but when I dailed them in, it was satisfactory. With a HUGE mid range and nice top end. But the bottom was finicky.
I think he's just suggesting the "headache if you want it" advise.
I was told to use the same fcr's that came on the 95 model since it had a similar plastic base to bolt up to the 96+ airbox.
Now Ice, you had the carbs with a 1/4 turn throttle. The throttle opens faster, and the carbs are better design in general so that is why you have the better response...I'm guessing.
I want to add the fcr's and I'm waiting for a deal to come by.
-Frank

[Sardi]

Guys,

I have a ZX7R track bike, I have just aquired a race tuned engine for it.

Question: Is it nescessary to fit the 41mm carbs, or will the engine perform Ok with the standard carbs?
Also, does anyone have any idea on the price of a new set of Kehin 41mm FCR carbs or even secondhand? I have seen a set on Ebay for £450 - seem expensive!!

Cheers,

Steve

[davewaibel]

I have them on 2 of 3 of my bikes- because I like them- they sound awesome- there is a hp gain on the suzuki, but there is NO gain on zx7s' 96-03 models, Sudco tried real hard to discourage people from spending 1000.00+ and expecting 10-15hp gains,- there can be gains, if your putting JE hi compression pistons, and cams, etc- but no gain on 'stock' engine- also no choke circuit, unless you have the factory 41 fcr carbs. On my suzuki they cleaned up everything and lots of open space without the air box on the bike.