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Discussion Starter #1
Having too much time on my hands I created a spreadsheet with specs, including hp/weight for several bikes, including the ZR-7S. The numbers for hp/weight were as follows: ZR7 = .15, SV650S = .18, Bandit 1200S = .21, ZX11 = .21, and FZ1 = .26. Now hp/weight doesn't tell the whole story of bike performance (I expect gearing, and torque also come into play). But to get hp/weight to match the Bandit 1200S for example, a person needs to either increase hp up to 90 (from the stock of about 67), or decrease weight to 325 - netiher of these things are going to happen with tweaks of jet kits, and after-market pipes. So what I'm saying is, if a person would spend say $1,000 on a jet kit, dyno time, and a new exhuast pipe, I think the best hp to weight figure would be about .17 (increae of hp to 71, and decrease weight 20 lbs. by installing a jet kit, and after market exhaust). Call me a wet blanket, but to me, its not worth it.

That being said, I can't beleive for as long as the 750 engine has been around, that there is not a re-bore kit out there for the 750cc engine. Something to increase the displacement to say 820cc. Now that might be the most sure way to increase hp, and torque. A turbo miight be the only other way to SIGNIFICANTLY increase performance.

- Woody

PS - Anyone seen an accurate quarter mile time listed for a stock ZR-7/ZR-7S ? Somewhere I read it was just over 12 seconds.
 

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hey woody :) while i agree that the hp gains alone are not worth the money there are other reasons for doing mods. much of what we're doing for hp also smooths out the power curve, makes the bike more rideable and gives it a custom look. for example, you could do a jet/pipe/air cleaner along with drilling out the epa plugs for around $300-500. this would give you more power, a more usable power curve along wiht better looks and sound.

plus, even if i bought myself a ducati/r1/<insert favorite super bike here> i'd still muck around with it. some of can just can't leave well enough alone. there's fun to be had tinkering with your toys no matter what they are. i used to hot rod air cooled vw's. anything with a v-8 would eat me alive but that didn't mean it wasn't fun :)

scott
 

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Hey Woody,
There is a rebore kit out. It's made by Wiseco and it is a 810cc kit. There is also another fellow(for some reason I can't remeber his name or shop) but a few guys here have talked to him personally and apparently he has a 880cc kit. Suppoesedly able to be done for around $1,000. I think it is going to be a project I will definately do sometime in the future.
 

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Discussion Starter #4
Scott,

I know what you are saying, there is fun and pride to be had on tweaking a bike or car. There semed to be a lot of posts (at the old forum anyway) about people grasping at how to increase HP, but I don't think anyone had run the kind of numbers that I did to really SEE what it would mean when they got done. I don't know, maybe I will buy a slip-on next year, mainly to drop some weight. $250 does not seem like a lot of money to lose some pounds, and maybe get a couple HP. Don't get me wrong. I really like my ZR-7S, I've probably had as much enjoyment from it as any of my "sport bikes". But I guess what I'm saying is that even with the typical tweaks, it will never be a high performance bike - and before owners start dropping $1,000 or more, they should look hard at the numbers and decide for themselves if it is really worth it. The ZR-7 has many. many good points, but a high-performance engine is not one of them.

NUTNDUN,

I just had to figure there was a bore kit out there. I hope that someone actually does the job, and reports back on HP/Torque increase.

Does anyone know of the quarter mile times, and top speed for the ZR-7S ?

- Woody
 

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I have to agree with Woody and Doug here, just the same as I disagreed with some on the ezboard threads some time ago. Tom :D

ps:
I am very happy with the Yoshimura round race slip-on and K&N filter additions, w/o jetting (yet) that I've made so far.
 

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Discussion Starter #8
Jarel - Thanks for the numbers.

RocketDoug and Tom,

I actually have a spreadsheet that lits price, quarter-mile time, 0 - 60 mph, and hp/weight. But I see what you are saying, to run another number like how much performance per cost. From what I can see, the ZR-7S is very competitive with the SV650S. The Suzuki costs a little more, the SV650S has a faster 0 - 60 mph time, but the Kawy has a higher top speed, and better quarter mile times.

- Woody
 

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all i know is this 20 year old 8 valve wheezer 750 spanked a mustang cobra. and the bike had me on it which means it wasnt even driven well, and it weighed over 750lbs.

i dont promote racing but that punk was asking for it.
 

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falcon said:
all i know is this 20 year old 8 valve wheezer 750 spanked a mustang cobra. and the bike had me on it which means it wasnt even driven well, and it weighed over 750lbs.

i dont promote racing but that punk was asking for it.
I love whooping them kids in the mommy and daddy's cars :)
 

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There is a good article on big bore kits in this months issue of Performance Bike Magazine. The Wisco kit is about $375.00 and includes everything except the valve cover gasket and the labor.
It increases the displacement to "only" 810 cc but increases the compression ratio from 9.5 to 1 all the way to 10.25 to 1. Flycutting the head you can take it much higher. Whoohoo! I will be doing mine in January when things are slow in the shop.
 

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Do you think the starter will be able to handle it? That's quite an increase in compression.
 

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Dirty Harry.... Moderator
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falcon said:
all i know is this 20 year old 8 valve wheezer 750 spanked a mustang cobra. and the bike had me on it which means it wasnt even driven well, and it weighed over 750lbs.

i dont promote racing but that punk was asking for it.
I got a Chevy Camaro Z28 in my mirrors real close to me today, too many times, so I shifted up fast a few miles, and the jerk was still too close. So...I came to a left turn familiar to me that involves at least 2-3 miles of hard lefts and rights and came to a stop sign and turned around and waited a moment, and here he comes to the stop with some stupid look on his face. And off I go back the way I came, and didn't see the Z28 again. Fun stuff. Tom,
Old enuff to know better, but what the F*&%. :D
 
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