www.zxrworld.co.uk

Hi all.

Firstly, my bike is a bit slow. It revs to the limiter, quickly, and willaccellerate very fast. But on a private road, I struggle to hit a ton. What can that be? The guy I bought it off could easily hit 120 so it's not restricted. It's also a uk model so should never have Been restricted. Only thing is it could have had a kit fitted to restrict it, but where? I think it needs a service and carbs lookin at but don't know what.

Also, the seat is damn hard! Where do I get a softer one??!

Ron Jeremy wrote:Hi all.

Firstly, my bike is a bit slow. It revs to the limiter, quickly, and willaccellerate very fast. But on a private road, I struggle to hit a ton. What can that be? The guy I bought it off could easily hit 120 so it's not restricted. It's also a uk model so should never have Been restricted. Only thing is it could have had a kit fitted to restrict it, but where? I think it needs a service and carbs lookin at but don't know what.

Also, the seat is damn hard! Where do I get a softer one??!

It could have restrictor washers,mine has and only just makes 100mph

You'll get used to the seat - either that or buy some memory foam or a sheepskin or something...

UK models weren't restricted like they are in some markets, but people do restrict them for the licensing laws over here. Did the bloke you bought it off just SAY he could get 120 out of it, or do you know that for a fact?

Because you say it is stopping around 100 I'd guess that is a restrictor doing it. You should get 135+ out of it normally, so even if it's blocked air filter and grotty carbs etc I wouldn't think it would slow it down all that much. It is worth giving it a full service either way, though, because it won't do any harm!

If someone had installed a restrictor or washers r smethng to limit performance, where would it be? What would it be? How do I remove it?

Spoken to the bike shop. They think it could be an import so it's restricted. They can check Monday with cahssis number. If not import, it's possible it has a restrictor kit on at the carbs. Like a washer with smaller hole to restrict flow. Could be that. May explain starting problemms. Also could be the exhaust, may need setting up properly on a rolling road. Hmm

Ho hum another restricitor saga................never ends does it ?

Import ZXR400 are restricted................to 110 mph.......this is achieved by a signal recieved in the cdi from the speedo.

There are a number of ways to overcome this..............

Remove the speedo cable

Replace the CDI

Fit a 10 ohm resistor between the speedo and the cdi...............on the brown wire ? I think ? You can get a plug in and play box to do this.............(I have one and it's for sale)

Replacing the CDI with a UK one

You can open up the speedo and bend the little switch that sends the signal to the CDI so that the CDI never gets the message that the bike is doing 110mph

If you just unplug the wiring connection between the speedo and the cdi it will go into a default setting and the bike will be even slower and only rev to 10K no matter what speed you are doing.

If the bike shop that sold you this bike sold it as a UK model and it turns out to be not so then I'd have some strong words to say to them if I was you...............and some money back as well.if you keep the bike. And I not trust them to service or maintain the bike for you if they simply just didn't know if or how it was restricted.


If it IS a UK bike and it's been restricted for licence requirements then it will have washers with holes in fitted betwen the cylinder head and the carb rubbers............easy to remove.

Good luck with it

I bought the bike off a friend so I trust him when he says it's not restricted and is a uk bike. I'll find out on Monday though. As for restrictirs, it could have washers on the carbs. Only one way to find out! The friend I got it off assures me it was once restricted but the washers have been removed. Only thing I can think o is that that tey haven't and that it's faster with him on as he's a lot lighter than me.

The CDI on an import bike has a yellow sticker on it...........

Also the speedo on an import bike has a small black wiring conector leading fron it.................. with 3 wires

You can also find restrictors in the top of the carbs that stop the throttle vales fully opening - between diaphragm and carb top.

Might be carb issues but if it's reving freely to the redline under load more likely the above.

Oh, CDI / Clock restricted you should get the same effect in 3rd, 4th, 5th & 6th - as soon as the clocks hit 180Km/h the bike starts stalling and doesn't catch again until you back off.