Who can cure my YZF problems?

davec105 · L Plate Warrior Joined: 27 Apr 2004 Karma :

Please help me.....
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I am calling all the knowledge and wisdom on this board to help me in my quest to fix my bike!

Problem -

Tacho displaying 7000rpm (fuel pump/sensor fault)

Things I have tried -

Tried another fuel pump.
Tried another CDi unit.
Tried another set of clocks.

I believe these are the most expensive things to try, and god only knows why I tried them first but you live and learn I suppose.

What do I try next?
I am not very good with wiring (never done it before), and the wiring diagrams make no sense.

I would check all the earth connections if I knwe where they were!!

Thanks in advance.....you never know, I might even send the person who fixes my problem a present!

I also have a misfire about 4 - 4.5k, and am getting backfires when I back off the throttle. I also get a puff of black smoke when I rev the engine. I have changed the plugs and cleaned the filter.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Exactly which model of bike is it? Is it fuel injected?

All the best

Keith
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davec105 · L Plate Warrior Joined: 27 Apr 2004 Karma :

It is a 1995 model, carburetted.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Guessing a bit here. You probably have a reserve switch for the tank. On the older bikes (and a presume your bike) the fuel pump is turned on and off by the cdi unit, using a sensor in the fuel tank. Basically when the fuel level drops the power to the fuel pump is cut, and the reserve switch bypasses the sensor.

Have a play around with this circuit. Might be worth just trying to switch it to reserve and try starting it like that.

All the best

Keith
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davec105 · L Plate Warrior Joined: 27 Apr 2004 Karma :

There is no reserve switch on my bike. I think 1995 on, they did away with the reserve switch, and introduced the fuel warning light.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

It would not surprise me if there is a circuit to cut the power the fuel pump after a short time. For example on my old FZ750 (which does have a reserve switch) the fuel pump only runs at full chat for a few seconds, then you have to flick the kill switch on and off. I presume this is to stop the pump running for too long when dry, and would assume there is a similar set up on your machine.

Sorry if this is no great help, but I have not worked on a bike like yours (YZF750 I assume). Stew might be able to help, or might have a workshop manual.

All the best

Keith
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davec105 · L Plate Warrior Joined: 27 Apr 2004 Karma :

I have the haynes manual, but there is no mention of this diagnostic fault signal. The throttle position sensor and exup fault are mentioned.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Probably best to try and get hold of an original Yamaha manual.

All the best

Keith
____________________
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Stew · Posted: 19:57 - 28 Apr 2004 Post subject:

I won't be a lot of help, but have you tried changing the fuel pump relay? I can hear my pump kind of buzzing when I turn my bike on with the key (along with the EXUP squeak) this also happens when I switch from 'on' to 'reserve' positions.
Last year I rode home from the Bulldog Bash (130 miles) with the fuel pumps electric connector disconnected. I didn't know this was disconnected and nothing was displayed on my rev counter, the bike seemed to run okay until around 100mph in top gear when it started to lose power.
AFAIK 7000rpm is a fuel level sensor fault, according to the Haynes you should check for continuity between the green and black wire terminals on the sensor side of the wiring with the tank the right way up.
<edit> I have just re-read your post and noticed you already have a haynes, so you will already know all that^ and also presumably if you replace the fuel pump you will have also replaced the sensor as it is all one unit</edit>
Sorry can't help really, it must be annoying though. Confused

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Stew · Posted: 20:43 - 28 Apr 2004 Post subject:

Is your bike the YZF750? Or is it the YZF1000 thunderace? On the 'ace 7000rpm is actually an error somewhere in the EXUP sytem (valve or servo).
____________________
"Unlike public school you don't need to have your arse up and your head down to go a long way...."

davec105 · L Plate Warrior Joined: 27 Apr 2004 Karma :

Yes it is the YZF750R.

I thought about the fuel pump relay, now and again, the bike seems to lose all power as if it is struggling for fuel, but when I pull in the clutch in runs fine. Sad

tank · Nova Slayer Joined: 05 Oct 2003 Karma :

sounds like your exup valve is jammed .my mates one was jammed open on his thunder ace giving a evil kick at about 5000 rpm now its sorted it just lovely linear power .he brought a one off ebay 50 notes there about 130 new i think
oh he tried cleaning his old one up does last long they warp out off shape