1996 YZF600 RPM Error Code and Revving Problem

[Alexomidov]

Hi everyone,
I'm located in the US and own a 96 Yamaha YZF600, this is not a Thundercat but the generation before that (I believe it was only produced in 1995 and 96. (will attach a photo if I can)

This bike has a different fuel pump assembly than both the FZR and the Thundercat, pump and sensor are both inside the tank with no mechanical petcock, there's only an electric button on the left side fairing that you can switch between on and reserve.

I recently went through the carbs and tank and rebuilt the fuel system, the bike runs good with 2 issues that might be related or not.

1- not at the start but after a couple minutes the tachometer starts cycling between the current RPM, 0 and 8000 RPM. My research says it's a fuel light issue but the light bulb works, the fuel reserve button works and the fuel pump/sensor connector is good (Checked it). The only thing haven't checked is the fuel level sensor, could that be the issue?

2- The bike doesn't like to rev over 7-8k. In 1st and 2nd gear it struggles at around 6k but if I push it it goes over and at around 9k it feels like a totally different animal, so much power! In the higher gears though, it won't go over 7-8k at all, in fact if I push it bugs down and goes even slower!

Does anyone know what the issue is here? I'm so confused!
Could it be all related to the RPM error code? Or I have 2 separate issues?

Appreciate any tips.
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Weekends are for riding not watching TV!

[A100man]

My guess

Two separate issues. I'd be stripping the carbs and looking for anomalies, or damage to diaphragms etc..
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[to v or not to v]

i believe the 8000rpm code means fuel level sensor fault

check that youve plugged the electrical wire from the tank back in if its the same set up as my ace.
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current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.

[Alexomidov]

[Alexomidov]

[P.]

Have you had the pump out? Assuming its the in tank insert rather than the inline 1 in 1 out smaller pump.

They have a filter on them internally, mine was absolutely wrecked and gave a very similar feeling.

Its fuel and gunk in there can cause a myriad of errors.

[Alexomidov]

[Alexomidov]

[Kawasaki Jimbo]

On point 2, my ‘99 ZX6R had similar issues at 55k miles. The Dynojet needles had corrosion or wear on them. I replaced those needles and jets and haven’t had a problem since.

https://i.postimg.cc/T1Y2JV3d/IMG_0185.jpg

There were marks on the diaphragm slides too (as shown) but I reused them without issue.

[P.]

Adding a filter in line won't be a problem but they tend to be directional.

Could be worth a strip of the carbs and check each part as above.

[Alexomidov]

[Alexomidov]

[P.]

Did you strip and clean them? Photos etc

[Alexomidov]

[A100man]