exup removal

[arkeye]

hi everyone,

been searching for a manifold/header/downpipe and have found a race one without the exup valve fitted. i had a look at the rest of the exup valve attached to the frame and im left with what i can assume being the motor to function the exup valve, it has an electrical plug going to it. can i just unplug it and remove it?

[plodder]

Usually unplugging the exup servo puts a CDI in a safe mode but does not cause it to be damaged.

I don't know specifically what happens on the 400 i.e. whether it will or won't rev out.

One easy way to find out though.

Removal of the exup usually causes horrible performance below about 4000 rpm (it does on my 1000 anyway).

[arkeye]

Usually unplugging the exup servo puts a CDI in a safe mode but does not cause it to be damaged.

I don't know specifically what happens on the 400 i.e. whether it will or won't rev out.

One easy way to find out though.

Removal of the exup usually causes horrible performance below about 4000 rpm (it does on my 1000 anyway).

well i bought this months 'performance bike' magazine and they tested one out bought from this company and it got great reviews. just keep it above 4000rpm i guess

[Evilchicken0]

That was on a ThunderAce wasn't it ???

The FZR400 is tuned to give horsepower high up the rev range, which is fine but you need to get there and to do that you have to pass through low and midrange. So Yamaha made the exup to give a smaller diameter pipe and produce better torque.
If you take away the exup you'll lose the low down performace below 6000 ... You can retune the carbs but thats dyno time.
If you fit the pipe the bike will still be ridable ... just a bit of a dog through town and pulling away

[Thunderbike_steve]

what happens with the cdi in safe mode? does it retart the ignition curve? does it reduce the rev limit?
Could be usefull to know if trying to limit power of the thunderbike? Or just pull off a plug prior to dyno testing but thats cheating and i'd never do that!

[Evilchicken0]

I don't think there is a safe mode on the FZR's. The later bikes probably had one as the CDI's become more complicated and the Injection models do ... mainly to stop you from riding on a shut valve and damaging the engine.

PS Arkeye ... don't mess with the restriction on these 400's they'll simply limit ti 12,500 revs in all gears

[spannerman]

you can get rid of the exup motor from your bike but you need to change the ecu from a standard one to the sp version there is a guy selling 2 on flee bay at the moment offer him £80 an he will accept this will also up the revs so you will get 14500 rpm
if the exhaust is a full race version a bit of rejetting will need to be done on our race bikes with ram air we are using main jets, 128 inside 2 an 130 on the outside 2 you may need slightly smaller if useing standard air box
hope this helps