The following theory was expounded following the consumption of several pints of real ale (Stella) in my local hostelry. The exup valve causes back pressure at low (sub 5000) rpm engine speeds, this in turn prevents unburnt fuel from exiting the exhaust due to valve overlap. At high rpm there is no time for the incoming mixture to get to the exhaust valve. This is the reason for the exceptionally good fuel consumption of my Gen 1, and a good reason for not removing the exup. Any comments most welcome.
it is a bit more complex than that,it works by sending the pulse back to the exhaust port which stops the incomming mixture from going into the exhaust,an exhaust can only be designed to work for a short rev range efficiently.but the exup only works on the mk1 fazer in this way,on the later fazer all it really does is to quiten the exhaust,it is the same as the valves on other make bikes
looked at mine the day
heared bike up cracked bolts for cover plate an both sheared
need to get easyouts
its all workin fine on the plus side
That's a bummer rjd1.
Best ask others about getting those screws out. I've got a feeling it's generally a down pipe off job.
Do replace with stainless, you can get packs of cap screws from screw-fix which are ideal. Just cut down to required size.
I bought my screws off Ebay and I got the correct lengths,if you see the state of my downpipes mine were fit for one thing,scrap.the screws holding the exup valve in place were non existent,I had to dremmel the heads off and that did not take long
