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throttle doesn't hit had

803 Views 6 Replies 4 Participants Last post by  bladecutter
I have a small problem with my 98 ZX-6R. When I roll the throttle hard the motor die down for a second and then accelerates. I have this problem at all RPM but it the worst between 3500 and 9500 rpm. I don’t know if this is a zx-6r problem or what. I also ride a 97 Honda F3. (The Honda belong to my girlfriend but I take care of it) and that does not have this problem. I have tried several things to get the bike to hit harder and faster. New air filter, new plugs and rechecked the gap after a while. I also pulled the jets out and cleaned them, and that didn’t help the problem. I’ve also ran carb cleaner though the gas. I’m going to be putting a pipe and a jet kit on it this winter. Maybe that will stop the problem. But if anyone has any suggestions let me know.
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Well, I bet the experts in this forum Rob Lee and SWJohnesy etc. would be better at pinpointing it, but I'd say sounds like it COULD be a jetting problem.

3 questions:

1) Is it just in a certain rpm range? Or does it happen at ANY part of the rpm range when you lay down the throttle. If it's in any part of the powerband when you roll on, may be a problem related to the throttle cable?

2) Have you checked compression?

3) Is there any aftermarket part(s) in the carburetors? Are the stock jets still in them?

If this is only happening at a certain range (ie/ around 4000rpm)... chances are it's a jetting problem that is likely pretty easy to fix.
If you're the original owner and haven't changed anything, likely not the jetting, unless needles have been damaged somehow. Then it's a tougher one to diagnose I'd say...

Where's that Rob Lee guy when ya need him, huh?
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Without a jet kit you can only richen midrange by shimming the needles. If it does it worse when it is cold than when it is warmed up it is too lean. Put a #4 brass washer under each needle. If it improves add washers until it goes away.

The washers only cost about a nickel apiece so if it doesn't work you aren't out much.
My bike is stock. No jet kit has ever been added. The person who had the bike b4 me is my friend brother. He never altered the bike at all. He put about 3500 miles on it between 98 and 2002. I bought the bike from him in February of 2002. The only thing that might be a problem is he let the bike sit in a barn for a summer and only put 300 miles on it in 2001. I thought maybe the gas tarnished in the jet and the float bowls. That is why I took the carbs apart and cleaned them. I look at all the moving parts in the carb and everything appears normal. i.e. the throttle plates open all the way the slides move freely. I can’t say really when the problem started because I was a new rider and didn’t get on the throttle hard. But now that I can ride a little better I get on the throttle harder. And this problem seams to be getting worse and time go on. At first I could live with it but now it’s too bad to live with. I did get a little improvement when I put new plugs in it. But it didn’t get anywhere close to what is should be.
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i used ngk. and gap them at .72mm. my onwer manual said i should gap them .7mm-.8mm.
Your carbs may appear clean, but sometimes they aren't.

And a couple other things to do:

Change the fuel filter,
Synch the carbs,
Check the float levels,
Check the idle mixture screw settings.

Any of the above can cause the problems that you are experiencing. Might even be a combination of of them.

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