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Discussion Starter #1
I bought my ZR-7S a few months ago and had to clean the carbs because the previous owner had it stored for a couple of years without starting it. So I got those cleaned as well as other issues and got it ride ready, but recently I was curious what the bike could do and went WOT in fifth but found I couldn't accelerate past 80mph and rpms wouldn't go over 9000. The bike already had a K&N air filter installed as well as a Muzzy's exhaust. So now I'm just curious as to what maintenance I can do to remedy this. Thanks.
 

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will it go over 9k in lower gears?

What happens at 9k and 80mph? Does it start to stumble or run ruff or does it just feel like it has no more power to go any faster/higher rpm?

From what I"ve seen when a motor runs out of steam like that it's an air/fuel issue or an ignition problem. Of course there could also be other causes that I'm not privy too!!
 

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9,000 rpm in 5th should be about 120mph.
So, if I read your post correctly, you cann't rev beyond 9,000, or accelerate beyond 80mph in 5th.
9,000rpm in 3rd should give you over 80mph! so can you coax it faster in the lower gears?

It may be worth checking your ECU against a standard unit i.e. are the reference numbers the same.
Restricted versions of the ZR7 were sold into some markets, also its possible that someone has fitted an ECU off a different bike (ER5 maybe) - maybe that's why the previous owner stored it for a long while without starting it!

Of course, all of the above could just be confusing the issue and the problem's just a mouse nest in the airbox.
 

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Discussion Starter #5
The bike has been like that since I got it. I have suspected that rejetting could be the culprit, but I've heard that this could be a sprocket or gearing issue as well. I can get the rpms to rev into the red easily in first gear, and it becomes gradually harder the higher I gear. I can reach that speed in 4th as well. But when in 5th, I have the throttle wide open and it just doesn't have anything left. No sputtering or anything abnormal, just no more juice.
 

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your bike...

I would personally remove the carbs from the bike, and look at the main jet sizes... If they are stock, go up, as a starting point, like 2 sizes, and raise the needle 1 clip if it has one, or else shim it up with a thin washer,try that, and get some plug readings... I am betting you see an immediate improvement.
 

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Discussion Starter #7
First off, thanks for all the replies. I looked at the main jets to see what size they are, which I still don't know or how to tell, but I looked at them and noticed the third carb's jet had gotten regunked. So I cleaned that and started it up and it made all the difference. I haven't taken it out for a real test yet but just going down my road and back I can tell that the power is definitely there.
 

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your bike...

Thats cool, that you found an issue... but, still betting there is more to be had with proper rejetting...

It surely is running a bit too lean, what with factory epa jetting and K & N filter and pipe mods...
 

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Discussion Starter #9
That is still an issue that I will be looking into. The previous owner said that he rejetted it a few years ago with a K&N kit, don't think they have those anymore. Is white exhaust an indicator of running too lean?
 

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your bike...

White exhaust is usually indicative of moisture/water... it is just steam, and normal, when starting a cold bike...blue, would indicate oil being burned... Black would indicate a too rich condition....

They stamp numbers on the main jets, to identify their sizes... You can compare those numbers to what the manual says came stock, to see if it indeed has a jet kit in it... same with the needles...
 

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The ZR may not have enough power to redline the tach in 5th gear. I never tried it. But I do know that it will hit redline right around 100mph in third gear so I'm not understanding your 80mph top speed in 5th.

I also know that the ZR-7 has a small airbox and at higher rpms it is actually a bit rich because it cant get enough air. With the bike having been rejetted it might be difficult to get a good baseline starting point but I would fix whatever underlying problems there are before fooling with the jetting. It is very diofficult to get the carbs and fuel system completely clean without re-clogging issues as you already know.
 

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Discussion Starter #12
I got the carbs synched back up and everything is as you guys said it should be. Haven't opened it up in fifth yet but I can tell I won't be having to have the throttle wide open to do 80. Next I'll be looking into the air/fuel situation to see it rejetting is in order. Thanks for all the help guys.
 

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Here's another thought. Got my bike back from the repair shop and found that at about 7k rpm's it would start to cut out - felt just like a rev limiter. Eventually found one of the gas tank breather tubes had gotten pinched. Quick fix and definitely resolved the problem.
 

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i got a zx7r 2000 model does fine 1st, 2nd, and 3rd gear but as soon as i hit 4th it starts acting like it is lagging and cant get it above 80 and it wont get over 9000 rpms
 
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