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?

[ragedigital]

I ran my 96 FZR600 without the exup valve and servo. I simply unplugged it from the CDI.

You may have to retune your carbs for the higher flow...

[csofos]

Wait a minute. You can unplug the exup servo motor conection, but the valve will remain in closed position into the exhaust. And your engine will run poorly. You have also to remove the exup valve mounted in the exhaust. That's easy but you must have a new tap (handmaded) to close the non-exup exhaust manifold.

[ragedigital]

Let me clarify. I removed both the exup valve and the servo. I simply reused the exup valve cover and put a small bolt through the remaining hole to close it up. I ran it like that for quite some time before getting a full V&H supersport system.

So, yes, if you remove the servo, make certain to remove the valve as well.

[csofos]

Let me clarify. I removed both the exup valve and the servo. I simply reused the exup valve cover and put a small bolt through the remaining hole to close it up. I ran it like that for quite some time before getting a full V&H supersport system.

So, yes, if you remove the servo, make certain to remove the valve as well.

I did that to my fzr 400 once: i removed the exup valve and servo unit. But the engine run very poor in low-mid rpm. That's because the header pipes are too wide (the exup valve provide for making them narrow when on low rpm) and that's why there's no power on that rpm level. No back pressure.

So i put the exup valve back on position. If i had a new (narrower) header, won't need it.

[sbutler]

I have had long talks with my tuner about this exact issue. If you remove the exup you loose low to midrange performance. The bike has to be tuned to run without the exup. You will never get the same low end torque, so its a big trade off. You remove the exup, lose low to mid ridabillity & gain a few extra horses up top were you rarely use it.
My, & my tuner's advice [for what its worth] leave the exup on & just fit a good muffler/can you will gain a few horses up top, via better breathing & still have all your low torque.Win,win.

[ragedigital]

You remove the exup, lose low to mid ridabillity & gain a few extra horses up top were you rarely use it.

This is true if you use the bike for street use only and it will not see the track. I used mine at the track, where the FZR was born, and the "top" end is where it's at. That's the real horsepower.

There are ways to correct the mid-range loss. A jet kit can help significantly with that. Low range was never the bike's strong suit, but then again, it was never the strong suit of many Jap bikes.

[the_finch]

Another option you could go with is to get that race header and a stock shorty slip-on off of the new R6's. They have the exup valve built into the can instead of the header like the older bikes. You might have to use the newer cables, but I don't have exup, so I honestly wouldn't know. I you could get that to work, you could have your cake and eat it too.

[sbutler]

You remove the exup, lose low to mid ridabillity & gain a few extra horses up top were you rarely use it.

This is true if you use the bike for street use only and it will not see the track. I used mine at the track, where the FZR was born, and the "top" end is where it's at. That's the real horsepower.

There are ways to correct the mid-range loss. A jet kit can help significantly with that. Low range was never the bike's strong suit, but then again, it was never the strong suit of many Jap bikes.

Maybe I think we are talking about different bikes, but I can tell you I race my FZR1000 & we have had it on the dyno & it makes huge torque.
In fact it makes max torque at 3100rpm & holds it to 11500rpm. So my EXUP is staying put. Not worth losing the torque to gain a small amount of topend. Just our pinion.

[ragedigital]

Maybe I think we are talking about different bikes, but I can tell you I race my FZR1000

Yeah, this is in the FZR400 forum. I was talking about my 600. Many racers I know ditched the EXUP for full systems on the 400 and 600 platforms.

I think just about anyone would agree that the 1ks require it. I didn't realize that you had a 1k.

[alfchallis]

how do I get my fzr 400 to pull beter once I unplugged the servo and tied back the valve to an open position please help need the bike running for
work

[willandrip]

Why did you do that ?

[alfchallis]

the vavle and servo doesnt work at all thought if I could disconnect it that the bike would run beter but it doesnt is there any easy way to do this that the bike can run beter please

[DonTZ125]

Sure - service the valve and cables, so the EXUP works properly.

[Evilchicken0]

If you have a 400 on the road its better to keep the exup. It matches the exhaust size to the revs below 8000.

There could be three things wrong with your bike, either the exup is jamed, the cables are shot, or the servo isn't working.
Follow the exhaust pipes down and you'll find a chrome cover by the side stand, take that off. Behind that there's a pulley with two cables on it. Are the cables frayed ? If so they'll jam up the system. You can't buy new ones but you can get a kit from Venhill (England) to replace the cores.
Take the pulley off so you can detach the cables. Put the pulley on again and check it can rotate back and then forward freely. If its jamed you'll probably need to renew the bushes ... it can be a difficult job without the right tools - take it to a garage.
With a all this disconnected plug the servo in again and turn on the ignition you should see its pulley wheel rotate one way then the other. It should make a "weep weep" sound.
After doing all this you'll at least know where the problem is and we can advise you better