ZX7R - More HP required

[MBP]

Hi Nick,

There are absolutly heaps of mods you can do to a ZX7R to get that extra little HP gain here and there, listed below are just a few that i have done on my 98 ZX7R and explanations of why i did them.

1 - Cut the tanks off the bottom of the plastic ram air tubes and plastic weld a flat section to the bottom of the tube(make sure you put a small drain hole in the bottom of the tube to drain water say 5mm).
The ZX7R has that HUGE tank at the bottom of the ram air tubes for two reasons 1- to catch any water that goes into the ram air duct, and 2 to make the induction noise quieter, removing the tank eliminates the turbulance of the air flow going into the airbox and gives a little additional air velocity.

2 - Carb float bowl modification.
See link
http://homepage.ntlworld.com/webzxr/zxr750r/index.html
go to
Tech Tips
93 - 03 models
Float bowl vent mod.
This Mod pressurises the carb float bowls to the same pressure as the airbox basicly when you get the ram air effect and your airbox is under positive pressure it pressurises the float bowls and pushes more fuel in. Makes a huge difference, and costs $0.

3 - Jet Kit

4 - K and N air filter

5 - Adjustable ignition rotor
For more responsive acceleration, I have mine set at + 3 degree's.

6 - Quickturn throttle
For a more responsive throttle, I use a standard 05 ZX10R trottle tube as this is a quick turn unit for a ZX7R, no mods required just change the tube.

7 - Chain and Sprockets
Changing from the standard 525 units of the ZX7R to a 520 conversion and aluminium rear sprocket improves acceleration and reduces 980grams of weight.
I use a renthal rear sprocket and regina 520 chain.

8 - Full exhaust
Not the cheapest mod but makes a massive difference with the above mods.
I currently have an ex TKA full Titanium system on mine.

Hope the above helps,

If your after any additional ZX7R info just drop me a line.

Cheers,

Matt

[katanaman]

all of the above but with a 950 engine sloted in. MMMMMM torquy fun!!!!

[Bogan]

Resurrecting an old thread, I've just been talking to a dude who tunes bikes down here in Canberra. He said something about needle somethings that wear out in carbies at about 60,000 and mine has 93,000km on it. He's talking about jet kits and needle bodies or something like that.

I just wanna make sure I'm not going to lean it out and destroy it at Phillip Island with the Yoshi on it, so while he can balance the carbies and check the AFR he might not be able to adjust that.

I don't want a bajillion horsepower but I do want the bike to behave itself and the mechanicals (engine and gearbox) will be the only bits untouched after I flush the brake fluid and replace the pads.

Factory Pro jet kits, where to get them, do other kits for other models fit a '91 ZXR750?

I'm a bit of a n00b at all this bike stuff, who can help explain and maybe source parts and stuff?

[Tack]

Resurrecting an old thread, I've just been talking to a dude who tunes bikes down here in Canberra. He said something about needle somethings that wear out in carbies at about 60,000 and mine has 93,000km on it. He's talking about jet kits and needle bodies or something like that.

I just wanna make sure I'm not going to lean it out and destroy it at Phillip Island with the Yoshi on it, so while he can balance the carbies and check the AFR he might not be able to adjust that.

I don't want a bajillion horsepower but I do want the bike to behave itself and the mechanicals (engine and gearbox) will be the only bits untouched after I flush the brake fluid and replace the pads.

Factory Pro jet kits, where to get them, do other kits for other models fit a '91 ZXR750?

I'm a bit of a n00b at all this bike stuff, who can help explain and maybe source parts and stuff?

There is a kit made specifically for the 91 J model bike. I got one for my 91 ZXR750 but I had to order it in from America because the kit was (supposedly) not available any longer (in Australia?).

I put the kit through the carbs and then took it to a Dyno.

They were only able to get 100hp out of the thing. Part of the problem, so I'm told, is that this particular model bike is the lowest horsepower 750 in the range because at the time, supposedly, there was talk of restricting sportsbikes to 100 hp, so they went ahead and restricted it. Dunno if that's true or not, however the 91 ZXR750 does have low horsepower compared to the other later bikes.

If what I've been told is correct part of the problem is the cams however I dunno if it has a lesser compression ratio than the others also or maybe smaller valves or ports etc.

It is also possible that the std carbies venturi size is a bit small and so going to a larger bore carby may be helpful. For example the RR version, I believe, had Flatslide carbies on it which I would bet had bigger venturis than the std Kiehin CV carbies. I have been told by one person that the flatslides add about 20% horsepower however I would think that is a bit much for just carbies alone. Maybe it just feels like 20% Apparently the flatslides are a bit of a "all or nothing" thing. When you twist the throttle they supposedly snap open pretty quick which might make them street unfriendly. I'd also guess that with bigger venturi sizes that the power will be more peaky and you might lose some low to midrange torque.

Anyway, I'm getting a set of flat slides and the bike will be dynoed again so we'll see what they add (allowing for dyno reading variations of course). I guess I'll find out what happens.

[Cedric25]

BUMP??

I think that's about right for a ZXR750 - 100hp.. I know about the restrictions put in place - mainly in Europe so local ZX7Rs aren't affected but still the performance is asthmatic compared to anything 600 and made after 2002.. How'd the flatslides go?

I'm going through a similar phase though with my ZX7R; I love the bike, especially the stability and cornering ability but when I have R6s and CBR600RRs pass me down the straight, and have to really plan my passes in the corners due to the lack of power, I question whether I shouldn't just upgrade to a ZX6R(R) to be on modern machinery, as opposed to sinking yet another $1K to upgrade some components on the 7R, when it owes me so much already.. Especially when one can be picked up for $6-7K..

I know I'm absolutely nowhere near the limits of the 7R's capabilities (1:55's at EC) but it seems like a superhuman effort just to keep up and pass some guys on 600s let alone the 1000s, and kind of disenchanting... Although it's a great feeling to pass R1s at turn 8 with my knee on the deck..

Any thoughts would be appreciated.. cheers!