FZR400 Exup exhaust question

[chesterch05]

Hi,

im planning to buy an FZR400 1989 for a project bike but the EXUP exhaust was removed, is this still a good buy or the bike would be useless without it? Whats the difference with and without the EXUP valve?

thanks.
still new to this type of bike hehe

[TomcatMJ]

Hi!
Not every 400 has an EXUP-System included...the first generation 1WG (Modelyear 1986) and all 3BF don´t have an EXUP-System, a 3FH could easily be changed to a Non-EXUP Version by using the TCI of a 3BF and an exhaust without EXUP (and putting the then needless EXUP-Servomotor in a box instead of the Motorbike)...with a 2TK, 3EN1 or 3EN2 you should either run the EXUP-Servo without cabeling to the EXUP-Valve or use a simple EXUP-Terminator/EXUP-Eleminator (costs only a few € to build one if you can handle a soldering-iron, 5-10 € depending of where you buy the 2 transistors, the capacitor, the 5 Resistors, the Plugs, wires, small housing like a used empty screwbox and a piece of DIY-Platina)...
The differnece is that theres a small power-hole between ~6000 and ~8500 rpm and the noise and CO-Values differ a bit (bit louder in several rpm-ranges without EXUP, better CO-Values with EXUP)....but the 3FH with EXUP for example use definitely the same jetting as the 3BF without EXUP and the only real differnece between the two Models is the EXUP-System..

Edit: And as a result of this a slightly different ignition-diagram what is the reason why it makes sense to exhange the tci if you want to run a 3FH without EXUP instead of attaching an EXUP-Terminator instead of the EXUP-Servo

[willandrip]

In real life road use you are strongly advised to have the Exup fitted.
The engine is as flat as a Haddock if one is removed from one that it was designed for.
The valve size/valve timing overlap and exhaust port along with the exhaust bore was specifically designed so as to give max performance at high rpm and yet STILL retain tractability at low rpm AND easy starting from cold. .
On a race bike they are removed for weight loss BUT the lower rpm range is rarely used.

On the road you will find you need to constantly rev the engine and slip the clutch in traffic and at take off from standstill.
This very soon results in unnecessary wear on other components. It instantly results in uneccessary fuel cost expenditure.
Thousands if not hundreds of thousands of man hours, money and Dyno time have been wasted previously by owners attempting to "jet" around this scenario ...I have yet to see a proven effective solution posted. (except by those who have upgraded from a variable ratio transmission scooter and find the power deliver "awesome" as they know no better Lol.)

If a true 89 it is a 3EN2 and depending on what has been discarded and how it has been blanked off then it is a relatively simple task to replace the valve. Value the bike accordingly.

[Evilchicken0]

if you're in the UK you could be looking at a twin headlight model or a single trapezoidal light (with 2 small paralever lights inside) - the trapezoidal will be a 3tj, which is slightly better than a twin headlight model.
Either way it's better to have the exup in place than not - check the condition of the pipes before you buy and if they're very rusty it's best to avoid

[willandrip]

a 3tj, which is slightly better than a twin headlight model.

Rubbish...Lol.

Nah..Boris is correct actually..gives access to cheaper/better 17" rear rubber....but they look only half as good as a twin lamped model...

[Evilchicken0]

Everybody loves a TeeJay