www.zxrworld.co.uk

This is our experience on my son's ZXR400 .........

Check that your CDI IS a UK spec - blue sticker. Restricted CDI's will not allow revs past 10 500. (with popping & banging from the exhaust as the CDI limits the revs by timing retardation) . We changed from a JAP CDI (yellow sticker) to a UK one, and immediately got 14 000 rpm and a much smother ride (the ignition map is different).

Carb restrictors do not limit the revs directly (e.g. when revving in neutral or in low gears), just the power (like running on part throttle). You can see the restrictors if you take the airbox off, lift a carb slide and peer down the carb venturi - if you see some plates with holes around a 5p coin size, this is the carb restrictor. These limit the power to 33hp - good for about 80-90 mph good - enough for a new rider I think !!

The speedo limiter limits speed to 180km/hr (120mph - ish) - I think this is JAP speedos (i.e. not mph ones) are the ones that have it - not sure as we haven't tested it. Our bike has km/hr clocks but we cannot see any wire destined for the CDI. Whether the UK CDI ignores this input we do not know - we will have to see once we take the carb restrictors out...You can read about the fixes on other posts........


Cheers


Charles

Hi checked down carbs and there fine no restrictors also cdi unit has blue sticker. revs all the way in neutral.
Think im going with balancing and cleaning out the carbs as the other day it splutted about 9k then kicked off all the way and i nearly put myself into the back of my mates bike like a sudden nos boost, lol.

Thanks for your reply think its just a good set-up should sort it think i can rule out restrictors.
Gonna reset all plugs, balance carbs and give a full clean etc . il report bck when i have got these all done thx again all.

tried to balance the carbs abd just couldnt get them all the same so annoying. How much would a full carb set-up set me back by a garage??

balancing carbs is easy mate unless the carbs are shagged, garage will charge about £30 for balancing providing nothings wrong with them.

Hi

If the bike won't rev past 10k, and pops & bangs at 10.5k (i.e. hitting the rev limiter), it is possible that you have a non UK CDI (yellow sticker) or the loom from the rev counter is not fitted correctly.

The carb restrictors are simply "washers" with a hole the size of a 10p piece fitted below the carbs. They do NOT directly affect the rev limit, only the power - think of it as running at 1/2 throttle all the time. Take the airbox off, lift a carb slider and peer down the venturi - you'll see them if fitted.


BTW a UK CDI (blue sticker) also has a different ignition map, and our bike was a lot smoother when we fitted one.

Charles

Sorry folks - saw I'd replied already to the restrictor question - DOH !!


Balancing is easy- we use the Morgan Carbtune which works really well. Need to get the revs to about 2500 to get enough vacuum and then balance carb 4-3, 3-2 and then 2-1 in that order. If it doesn't set properly I'd guess you have an air leak somewhere.


Charles

Im just going to blow the dust off this forum for a second.

I was out for a ride on a private runway the other day when I hit a 110mph and then stopped accelerating. Clearly has been limited to 110mph. Thing is it revs to 14000rpm, does about 50-55mph in 1st so dont think its fully restricted.

I have an import with KM clocks but been converted to show MPH on the KM clocks.

Is it a case of following the instructions on this link?

http://www.zxrworld.co.uk/zxr400/revlimiter.html

Thanks

If you have a clock with MPH on it then you wont need to bother with that. Id check the following

-Is the CDI a blue (UK) stickered one?
If you have one then theres no reason why it shouldnt rev out to 14.5k unless theres a fueling/running issue.

-If not, check round the back of the clocks for a spare twin terminal connector block coming from the loom.
If you have the terminal block and nothing is connected to it, then the CDi has a defualt setting where the revs are limited to 10k, this in theory should stop you going above 100-110 mph.

I really must get round to making a guide for this to help people work out what they have or havent got.

Although you have checked for washers in the carb inlets , make sure you are looking in the correct place.
With the airbox off, you will have to open the throttle and lift the slides to lookright through the carbs and into the inlets.
The washers are possibly 3-4 inches away from the airbox and are on the engine side of the inlet rubbers.
You may need a torch to see right in and if you see anything blocking the inlets it will be the washers.

cargo wrote:The little screws that tighten the clips that hold the carbs on are a pain in the ar5e to get at

I use a flexi shaft screwdriver and it works really well.

I can't see that there would have been L's on it as you can't ride a 400 on L's unless you were accompanied by an instructor... i.e. someone doing a DAS test...

As for his VFR beating it that is quite likely anyway as they are pretty torquey....On standard gearing my vfr would accelerate quicker than the zxr coz it pulled from a lot lower.