Hi guys,

Hi currently have a se7en with a zx9r engine, yes it's the dreaded 'C'

Was out doing some testing on track today for the first time and towards the end of the day i developed gear problems. I was very occasionally getting a false neutral between going down from 3rd to 4th, however at the end of the day it was pretty much impossible to find gears coming back down the box from 6th. I had absolutely no problems going up the gears from 1st right up to flat in 6th but I kept getting neutrals and then it would find a gear and sometimes slip out of it again.

I also have a digi-dash with the gear indicator which has always worked fine but at the exact same time as the problems started the gear indicator started playing up and would only display 1 or 2.

Has anyone any idea what the problem could be? I'm going to get the engine stripped down but just wondering if anyone could give me some advice.

Thanks,
Paul

I don't know much about the specifics and quirks of the ZX9r engine but usually popping out of gear is a sign of worn dog teeth, a bent shift fork, or a sticky shifter mechanism.

It might be worth checking the shifter linkage and maybe dropping the pan if it will give you access to the forks and gears.

[Edited on 21/2/10 by atm92484]

Is your gear linkage still fully attached.
Have had similar problems shifting one direction only and this was due to too much play caused by a slackened bolt.
There was just not enough gearstick travel in one direction and would get false neutrals and unable to shift.

Failing that you may have bent the selector forks inside the box.

Thanks for the replies!

Everything looks fine regarding the selectors but I'll check everything is tight and working as it should.

I'll just have to get it stripped down and checked out. I'm starting racing at the end of March - I would maybe be safer upgrading to an 'E' series motor.

Bent selector fork mate, definately, I replaced one for a mate a few years back, you can fit the E' model gearbox straight in if you can find one. When/if you change the fork then make sure that you change the shaft as well.

we had exact same problem, built locost with a C motor on 5000 miles, lasted two meetings at Cadwell with a Flatshifter. Started leaping out of third, mindful of weak box in the C series, we changed to an E - done 1 meeting since, and for the first time went home when we wanted to rather than when we had to !!.
Dont bother with the C for hard track use. The first time we had problems, I was faced with the same dilema, and took the box apart - oil and gaskets alone cost best part of 150 quid (deoosn't include forks or gears)- used E series motor 450 quid.
Put the cost of fixing the C toward a later engine. Besides, strip and rebuild takes at best a full day, if you have the new parts to hand.
hope this helps

ps stripping the c box was interesting, but an expensive exercise in curiosity !

Just had another thought
Changing to an E is relatively straight forward.

You will need to get the E series ECU and connecting plug - change or just add this to the existing loom (we now have two different ecu plugs on the same wiring - so we can plug in EITHER a C OR an E ecu depending which engine is installed but NOT BOTH at the same time).

All the engine electrical conns are the same, except the cam position sensor - there isnt one on the E series so just tape the plug and wire out of the way.

If you buy a bare engine, your C Carbs are a straight swap (E series carbs are jetted differently, I beleive to do with heat issues, though ours has runs OK up to now on C carbs).

The exhaust ports are slightly larger on the E, but the C pipes still fit, not an ideal situation if you ask an engine tuner, but irrespective ours still goes like stink when we road tested it. ( the exhaust will probably be altered when I have more time).

All in all it took a lazy day to do.
Soldering the ECU plug onto the existing wiring, fitting the baffle plate in the sump, installing the uprated Barnet clutch sprngs, and dropping the motor back in.

if you need anything else, only too happy to help

hope you sort it

Thanks for that reply ginger ninja - excellent detail and exactly the info I was after as I am currently trying to sort getting an E engine shipped over from England to N. Ireland!

How much different are the exhaust ports and how do you plan to alter yours?

The engine I'm looking at buying comes with everything, however I have mine dynojetted - does the same kit do both the C and the E? If so would I be better using the E carbs and getting it rejetted?

I'm starting racing on the 27th March so the C is out the window, it's actually already out of the car!

Thanks again for the responses.

quickest way to sort the exhaust - you will need an E manifold for the flanged pipe ends which fit into the exhaust port - cut these off and weld them to your existing exhaust, or if you are suitably adept make some from scratch. Assuming you current exhaust tubes are no smaller than E ones !
Our C carbs were dynojet and rolling road set - so we kept these, dont know if jet kit fits both - suggest you ask rolling road people before you take it. This tuning is a must and the best power increase (usually ) money can buy.