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Discussion Starter #1
I've been away for awhile, but does anyone know if there is a bore/larger piston kit available for the ZR7 ? If only I could get 20 to 25 more hp out of the engine, (up to say 85 to 90 hp peak) I'd be happy. Otherwise I may follow thru on plans to sell my '01 ZR7, and buy a carry over '01 FZ1.

It looks like slip-ons and re-jetting will get me only about 3 to 4 more HP. Not even close to my goal.

- Woody
 

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Woody, yes there is both a big bore kit and cams available for the ZR-7. Wiseco make an 810 kit with 10.25:1 compression and MegaCycle makes cams. Both companies have listings for the GPZ 750 which will work in the ZR-7. You can get the horsepower increase you are looking for but its going to require one of the more radical cams that MegaCycle offers--they offer six different grinds. If you call MegaCycle they can fax you a listing of their cams--they do not have an operating website as of yet 415-472-3195. The cams will run you about $400 and it will require you to send them your cams so they can do a hardfaced reweld on them. The piston kit will run slighly more than $400, plus a $100 or so for boring the cylinders. Don't forget the gasket set and valve springs! While the head is off, you might as well have it ported and polished--$300 or so ought to take care of that! If you have gone that far, you are going to need, at a minimum, a slip-on replacement muffler and a jet kit--another $400 ought to cover that! I'd add all this up for you but I can't count that high! :rolleyes:
 

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jeez tom, almost sounded like you were talking about real money there for a minute :~

actually, it reminds me of modifying vw bug engines. they're perfectly designed to run forever as is. touch just about any one thing and you've got to mod everything else to keep up.

scott :)
 

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Scott,
You know I have given serious thought to the piston kit. The added displacement and compression would help this bike a lot. It would also maintain the flat power curve we have all grown to love--and curse! The only problem is, fundamentally, it's tough tearing down a motor with less than a 1,000 miles on it. So for now, I'll keep riding and dreaming :z of 80 rwhp.
 

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stop dreaming! for another $1000 over the cost of the mods you can buy an old ninja or honda f2/3/4 and still put 87 octane in your zr-7 ;)

seriously though i know where you're coming from. it's fun to tinker even when you know you can get better results for less money off the shelf with a different bike. some of us just can't leave well enough alone :) personally, i'm sticking to monkeying with the suspension. i think you get better bang for the buck here than with some of the horsepower mods. and no matter how much i mod my suspension the noise from it never attracts more police :~

scott :)
 

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big bore kit

You can also get an 880 kit installed but the liners have to be replaced. They then bore the cylinder case out to accept larger liners and then bore and hone those to take the 880 pistons.

Unfortunately you will also need stronger bearings etc in the bottom to handle the increased load but if you have the money, I'm sure they have the time.
 

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Discussion Starter #7
BORE/PISTON KIT

Tom or others,

Any idea what the increae in hp/torque would be if I installed the Wiseco bore/piston kit, and left every thing else stock. (Or maybe I can't do that - are there other components that are mandatory if I install the piston upgrade ?) How much does the Wiseco kit cost ?

- Woody
 

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Woody,
You can install the 810 kit and not change anything else (internally). Because no one has done this yet, I would be guessing on the horsepower and torque increase. Assuming you have a slip-on muffler and jet kit, which would be the basis for maximizing further modifications, I would think you would get somewhere close to an 8 horsepower increase and about 6 lbs of torque (after jet kit and muffler). As I stated earlier, the piston kit runs about $400 plus cylinder boring. Contrary to a previous post, the KZ motor (which we have) is very strong and can handle massive amounts of horsepwer increase without risk--even the 880 kit (no bearing modification required)!

One of the owners of the shop were I get all my work done (including dyno runs) has a young son who drag races an old KZ 650 with the Wiseco 720 kit and GPZ cams. Though the bike is obviousley lighter than our ZR's, they are running consistent mid 11's.

The thing is, if you install the piston kit with new valve springs then you have the flexibility of changing the cams at a later date. If you have the valve spring already installed, changing the cams is then no more complicated than a major valve adjust.
 

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Wouldn't a big bore kit and cams require a new set of carburetors to really take advantage of these modifications?

Andy
 

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Andy--a new set of carbs would most certainly help, but it is not completely necessary. Besides, the only CV carbs that would fit would be the GPZ 750 carbs and they do not have the K-Tric device. While a friend of mine had is carbs off his ZRX1100, we measured them to see if they would fit the ZR-7--no such luck!
 

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Hi Tom,

I was thinking if you went with all the upgrades, a set of after-market flat slide carbs would be the way to go.

Andy
 

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This is bugging me!

To all,

In an earlier post regarding the 880 kit I mentioned you would need stronger bearings to handle the load increase from the upgrade.

Wrong!

Someone corrected this, Tom Droze I believe, and he is correct. You would not need upgraded bearings for this conversion.

Thanks Tom! It's good to know there are informed and alert readers out there!

I was thinking of the bore job in addition to a blower, cams and a nitrous kit. Carried away as usual.

Anyway, I just wanted to apoligize for the misinformation and reassure myself that I'm not a total twit.

Now, if I can just get this size 11 boot out of my mouth........!
 

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Wasn't there a turbo for the GPz750R? That should provide the extra flow needed for the bigger bore. Of course finding one and making the needed exhaust modifications might not be possible.
 
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I been looking into a big bore kits and a company out of TN. says the 880 kit they make for the GPZ 750 turbo would fit without any cam or bearing mods. Say it just a bolt-on situation. & it's been a popular request as of late. Company name is Horsepower Unlimited, Phone#615-824-6116
 

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Yes

I'll glady share my experiences with you, that's the whole point of this website. To share information. I would be grateful if you would post our Qs and As though so others can participate, I am a computer novice. Or better yet just post the questions here and I will answer them promptly.
Thank you,
R. Clayton
 
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