Sickly 2001 ZX6r, need backup please

[bacon]

Hi Everyone,

Recently I brought a street fightered zx6r for quite cheap which had been sitting in a shed for some time. I was told by the previous owner that it has issues once it hits around 110kmph which it didn't have before it sat. I took it for a ride and found that once you hit around 110kmph (in the higher gear range, around 7500rpm) the engine basically dies(like the ignition got switched off), then comes back again after a few seconds and back fires a bit, I really couldn't get it above the 110-120 mark without reving it up in low gears. So I started by cleaning out the carbs and checking the diaphragms for holes. Everything seemed ok, although 2 of the diaphragms did feel a little ..crumply? as I pushed them up and down in the carbs. Next I checked the fuel pump which seems to be pumping well when the engine is running, so fuel flow seems to be ok. I'm really no expert, especially when it comes to modern inline 4 engines as I've only really worked on simple air cooled singles. I haven't balanced the carbs as I don't have the tool for it. Could being out of sync cause this bad a problem? Here are a Couple other things I noticed which I suspect could be causing it:

*Small part of the air filter foam has come away from the border of its frame
*no holes have been created in the airbox for the correct RAM air removal mod(possible not enough air going to the carbs?)
*Haven't checked the plugs, but that is my next step.
*Thermostat seems to display the right temperature but doesn't start the fan (previous owner fitted a manual switch, possible electrical problem?).

Here are the pros:
*starts easy enough and goes through the rev range with no issues when stationary.

Any help is greatly appreciated. If there's anyone you know who can help without charging an excessive amount (I'm a pauper student) I'd be keen to get in touch.

Cheers,
Chris

[JimO]

im no mechanic so havnt a clue really perhaps its the coil?

[mossy1200]

Original speedo?

[bacon]

Original speedo?

Yep, I'm pretty sure anyway

[Katman]

Have you tried replacing the fuel filter?

[nodrog:Me]

Have you tried replacing the fuel filter?

Replacing it with what?

[bacon]

Have you tried replacing the fuel filter?

No, although I have noticed that the last owner has installed a larger car style filter

[haydes55]

vibes could cause a wire to earth out or an earth to break contact at those revs? does it cut out if it's revved to the same rpm on its stand?

stator issue?

if the bike just suddenly dies, it sounds more electrical than carburator. if the carb/fuel is an issue, it would splutter before dying, the spark plugs would still be working.

Sent from my HTC Desire 310 using Forum Fiend v1.3.2.

[bacon]

vibes could cause a wire to earth out or an earth to break contact at those revs? does it cut out if it's revved to the same rpm on its stand?

stator issue?

if the bike just suddenly dies, it sounds more electrical than carburator. if the carb/fuel is an issue, it would splutter before dying, the spark plugs would still be working.

Sent from my HTC Desire 310 using Forum Fiend v1.3.2.

When stationary the bike has no problems going through the rpm range, just once you hit around 110 the engine starts cutting out and back firing. I'm really praying its not electrical, long have I feared trying to solve electrical problems. In second and third I can get the bike up to speed and high rpm, the problem seems to occur only in the higher gear range when the engine is under more load. The previous owner claimed it was running up to 200kph without any problems before it was parked up and sat for a year which would seem to break my theory that its due to incorrect ram air modification. I'm thinking a well priced engine tuner is my best bet

[Vinz0r]

Have you fucked with how the air is directed for the intake? If so hook up the standard hoses and whatnot. Sounds like it's not getting enough air while moving at speed.

[AllanB]

First thing I'd check is the fuel filler - they are vented and if the vent is blocked they run fine at low speeds but cause a fuel vacuum type of effect as you go faster and the engine demands more fuel - engine will not rev/go past a certain point.


Easy way to check this is to crack open the fuel cap a bit and go for a ride. I'd advise you maybe duct tape a wooden (or similar) wedge in there so the cap is taped down but obviously open enough to breathe - if you leave it just open chances are you end up in a emergency stop or similar and have fuel piss out all over the hot engine.

So if it pulls cleanly when cracked open the fuel cap vent is blocked and needs clearing.

[F5 Dave]

No, although I have noticed that the last owner has installed a larger car style filter

I'd be losing that for a starter, even just for a test.

[FruitLooPs]

I'd be losing that for a starter, even just for a test.

Agreed, some of the larger car style ones have tiny outlets on them, between that the fuel vapor lock or a sidestand switch/tipover cutout - should be a simple enough solution.

Goodluck