1995 FZR1000 RU EXUP valve problems/running issues

RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

Hi I'm new to the forum and I have very limited knowledge of bikes as been out of biking for sometime Very Happy

I have just picked up a winter project FZR1000 ru but in fairly rough shape,its mot'd and the engine sounds tight. I intend to bring this bike back to life with some tlc and some new bits.It has a running issue,the previous owner said it popped and farted while riding and then cut out! After 5mins bike would start then repeat.

The bike starts first time but runs lumpy.

First thing I checked today was the exup valve on the collector box,its not working and the two cables running to it don't seem to do anything?
The cables run from a unit under the tank and from there connect to the ecu unit.

Is this a possible running problem as when you rev the bike it seems ok at higher revs but not on tick over or lower revs?

Any advise would be much appreciated

Cheers

Rob

Luckyfish13 · Renault 5 Driver Joined: 30 Nov 2015 Karma :

I'm not great withy the older bikes but I THINK (Note the caps) they're used to control the airflow where the down pipes meet letting the engine 'breathe' better at high revs by reducing vibrations from exhaust gas streams that join at different velocity. Quick google search says they work by opening a valve at certain angles pending on engine speed. It's controlled electrically (servo motor) so that could explain the problem especially at higher revs because there would literally be no exhaust if that valve was in its standard (almost fully shut) position.
Personally I'd be checking the carbs especially main jet for higher revs, needle jet for lower/idle revs, and the fuel and air mix screws.
Also check the spark plugs and HT leads just in case...stranger things have happened lol

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

Sounds like the valve is seized in the open position (good for top end, but crap for bottom/mid range)

There is a servo motor at the other end. If you remove the cables from it, does it turn when the revs increase?
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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

EXUP works to allow things to be tuned for high rpm without destroying low rpm power.

Basically the exhaust system works by bouncing pressure waves down. These move at a pretty fixed speed. At high rpm these will work well to bounce back to the cylinder head and bounce away again as the exhaust valve opens to pull out the next lot of exhaust gases. However at lower rpm the time it gets to the head will be in time to ram the next lot of exhaust gases into the engine.

The EXUP valve disrupts these pressure waves at low rpm.

They are well known for sticking. Bit of a pain to get out. If stuck open I would mainly expect it to have a flat spot in the mid range. Maybe a bit rough at low rpm, but not that bad

All the best

Katy
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temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

I'd give the coils/leads/caps a look at then dive in to taking a look at the carbies. Typical things to look for on an old machine like this are worn o-rings and gaskets (particularly around the float valve seat), the float valve needles and worn out emulsion tubes (needle jet) and needle (jet needle).
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RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

Cheers guys for the advise Thumbs Up

plenty to be getting on with then,going to start after the weekend off to the bike show Sunday

RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

salem1987 · Scooby Slapper Joined: 10 Sep 2013 Karma :

also careful undoing the bolts on the exup valve if you try to remove it..
9.9/10 they are seized and snap with little force if it hasnt been looked at for a while.

RobJPS · L Plate Warrior Joined: 02 Dec 2015 Karma :

Fizzer Thou · World Chat Champion Joined: 06 Aug 2011 Karma :

When I first bought my FZR-R I needed to service the Exup valve and I had problems straight away with the mounting screws.I ended up drilling them out to a bigger size and using stainless bolts instead of OEM mild steel items.

On https://www.exup1000.co.uk/ there is a supplier of a custom made SS pulley for the cables to mount as the OEM ones tend to rust badly.I may well be looking to buy one of these for my R1 as there are many similar parts for both.

I too had a problem with low RPM running.In the end,after replacing many seals within the carbs,I replaced the plug caps which cured the problem.On the Exup forum there is a post on how to install coil-in-the-caps from another machine and how easy it is to convert.A recommended modification but as I run with high output Dyna coils,not one that I will be doing anytime soon.
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