YFF750R Starting problems!!!???

[shane294]

Can anyone help me.........?
I've just bought a 1994 YZF750R. When cold or damp it takes a while to get it started. It also does this if it's left for a couple of days.
It turns over fine with no choke and I get one little puff out of it, then nothing, but it will keep turning over.
When I put the choke on and turn it over, she takes 2-3 seconds then tries to fire up. Then stalls instantly. This happens 4, maybe 5 times before it gets going and starts to warm up. She'll get upto 3000rpm at idle (on the choke of course) by her self then when I bin the choke it drops to 1100rpm but sounds lumpy. What should the idle speed be?
Even when I've been using it and it's nice and warm, it's still lumpy at idle.
Any ideas on the starting problems?
Also, when riding, I can hear a bit of a squeaking. haven't worked out where its coming from yet but I'm sure it's engine related (frequency increases with engine speed). Any ideas?
I'm an engineer but my knowledge on motorbikes is sort of limited.
If anyone has any helpful hints tips etc, your help would be appreciated.

Cheers

Shane
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Shane

[spikenipple]

Try balancing your carburettors. You could also run the bike with Redex for a tank to clear any (some of) crap from the carbs and cylinders.
The idle speed should be 1400rpm ±100.
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C50 > GN250 > XJ600 > SV650S K7 > 2001 RSV Mille R > MT-09, XR400R > 2005 Fireblade (trackbike) + 2022 MT-09 + ZXR400 race bike

[T1z3R]

check the operation of the exup valve, servo and cables.
YZF750s are prone to problems with them and it can cause problems with starting/idling.
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duck my sick!

[shane294]

Thanks for the quick reply fellas!

I was going to try Redex at the weekend. Missus is at work so I can clear it all through in one good ride into Cornwall .
The carbs have been balanced as part of a major service the garage did before I bought it.
EXUP Vv, servo and cables? I've heard a few people talk about it but am I right in assuming that it controls the fuel flow rate a certain revs? Is this cable linked to the throttle? I do have a good 20degrees of rotation on the throttle before it anything happens! would this be part of the problem? I thought it was suposed to be about 10deg?
I'm not sure where to find EXUP Vv etc, or what to check.
I'm not daft so if you could point me in the right direction I'd be grateful.
thanks again for you replies guys.

Cheers

Shane
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Shane

[T1z3R]

exup valve is in the collector box of the exhaust.
the exup cables are attached to a pully on the side which are operated by the exup servo found under the tank fitted to the right of the frame and the cables run from it to the pully for pull and return.

the valve itself siezes if not looked after and is the usual cause of less than normal idle/throttle response.

i dont have my service manual handy but i think the throttle free play is less than 20deg.
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duck my sick!

[phil2alp]

Is the battery in good condition?

I think a battery with a poor charge can lead to poor slow idling.

Just an idea.

[Hooky]

Shane: its the fuel pump playing up (common problem on this model)

Hence the "squeaking" etc.

It is a pretty easy fix for a diy but really would not cost too much at the dealers (under 1 hour).

Try evilbay for the pump , it might be hard getting a decent one though.

When you turn on the ignition you should hear a "buzz" for around 5 seconds, no buzz ? pump jammed.

Constant buzzing = fuel pipe bent or kinked (check this first)

Check good flow to the pump, then check the outflow, strange thing is the problem can be intermitant .

Good luck !

[shane294]

I'll hopefully get time over the weekend or next week to check out the EXUP valve and associated parts. Sounds very likely that this combined with the low idle setting could be the problem.
The battery is in good condition and is fully charged. There's no problem turning the engine over so it's definitely a fuel/air flow control problem.
There is actually a fuel pump on EVILBAY at the moment! i don't think it's this though. There seems to be no problems getting fuel at any other times other than when it's cold. when the ignition is turned on there is a 1-2 sec buzz (motorised valve....???solenoid....??? I assume:?). When I have all the fairing off I'll try and locate the squeak. Bloody annoying!
I seem to have mastered the art of getting it started now though. I'm not worried about waking the whole street up with a back fire or draining the battery and being late to work anymore
There's definitely enough for me to get on with for now. just got to find the time to do it
Thanks for your help and advice guys.
I'll keep you posted on progress, if there is any!

Cheers

Shane [/b]
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Shane

[flyboyn2144p]

Shane,

I have read through your plight. The pump is in the bottom of the tank and hence"internal pump". I have found that to help starting mine (Mine has issues at the moment) when first kicking the thumb switch to run open the throttle for a few seconds while the pump is running and then turn the switch on again and do the same thing and see if that does not help the cold start.

to get to the EXUp and to the pump you will have to remove the drivers seat bolt 12mm and flange and the 10mm bolt from the top of the tank. Put a towel on the front of the tank so you dont scratch the paint on the fairing stay bolts.

Directly below you will see the exup solinoid with what looks like 2 break cables attached and wires comming out of a black box. then on the bottom of the tank where the hoses attach is the fuel pump and Vacuum petcock(thats french for pain in the tuckas). the #1 Cylinder controls the betcock. if there is no vacuum there that the fuel will not flow! i currently am trying to make a way to remove this and have a manual accessiable fuel shutoff.

BTW DONT TAKE THE FAIRINGS OFF UNLESS YOU WANT TO!! YOU DONT NEED TO EVEN TO TUNE THE CARBS>> WAISTED AND POSSABLY DAMAGING (to the fairings i.e scratches, cracks) STEP!!!

Nathan