Kat 400 top speed issue???

[blackdog]

Hi Guys and Gals

I've still got me top speed issue on me Kat 400

1/ will run at 90/95mph all day long
2/ top speed the books say 120mph???? is this true??
3/ at 100 / 110mph for a quick blast 2-3miles all ok
4/ hold 100/110mph for a few more mile's and it fades, the revs counter just drops very slowly!
with the throttle kept in the same position in fades from 110-100-90-80-70-60, if you try and up the throttle it just nothin there!
it did this which lasted for about 2 miles I pulled in back to 1st reved like a goodun
back to top speed!
This happens all the time like something is set to do it!
I've been I the road with this bike now for over a year and pulls like a goodun
I also have toe Kat 400 tried other carbs and cdi same thing!
its just this over the ton issue I have!

So if poss can I have some imput from you other 400 Guys and Gals
top speed, niggley faults so on and so forth!

Thanks
Si

[johnr]

as fuel runs out of your fuel tap, air must get in the top to displace it. if air cant get in then the carbs will start to use more fuel than they recieve from the tank. this could be cos of a blocked air vent on the cap (its inside the tank cap lock) or it could be a kink in the petrol pipe restricting the flow of fuel, or a faulty or clogged fuel tap, it might even be clogged mesh filters in the carbs(just above the float valves) they can clog up with rust and scale from inside the tank. the fact that the engine revs perfectly in all gears suggests that your ignition and fueling are ok, but this fading sounds very symptomatic of fuel starvation, as when you slow down and the engine needs less fuel, the carbs can 'catch up' and then the power is returned.
first off, check the vacuum pipe that operates the fuel tap hasnt got cracked split or perrished, if it has then it will hold the fuel tap partly shut and restrict flow. if not, id put the tank on prime and run fuel out into a can, see how long it takes for the flow to slow down, if it does, then strip and clean out the filler cap and its lock. if the flow doesnt slow, then check the fuel pipe for kinking, and if its free then you will need to strip and clear the carbs.

[johnr]

speed restrictor is driven by a sensor inside the clocks, you can just cut the sensor wire and it will stop the restrictor operating.