ZXR Issues

[Thaeos]

I have in my garage at the moment one of those ZXR250C's ('91 I think) that can be pretty fun but it has a few issues:


Takes a long time to start, trying the starter constantly.
After starting it takes a long time to then be ready to ride, for the revs to settle and to not cut out if you close the choke. (you have to leave the choke open for a long time, if you close it before maybe 10 - 15 minutes the bike stalls which seems excessively long).
Adjusting the choke is very sensitive, a movement of 2mm can cause the revs to jump by a large amount, say 5000.
When riding, sudden twists of the accelerator cause the revs to slow and the bike does not start accelerating straight away, it sort of stalls but doesn't cut out all together, kicks in after a few seconds. If you do this while warming up it will cut out and stop completely.
Front wheel seems to always make a noise as if the brakes are slightly engaged, even when no pressure is applied to lever.


I was planning to drop it off over at Spectrum on the north shore for them to sort out but thought I'd ask here if anyone recommends somewhere else to go or any easy fixes I can do myself if they have any idea what the causes may be. I figure a good clean and balancing of the carbs and replacing spark plugs would be a good start but I don't really want to fiddle with the carbs myself.

[Akzle]

you could/should take the opportunity to learn to DIY.
None of it is that hard.

Elsewise M/C doctors will come to you....

[Drew]

Those are all common complaints on a small capacity inline four. You have to realise that these little motors are actually making huge power for what they are. So...

It sounds to me like it doesn't have a thermostat in it. Hence the long warm up. Replace it and the radiator cap even if it does have one, it might be stuck open and their cheap as.

The sensitive choke and hesitant revving, is probably the same thing. An air leak. As in, it's getting air some place other than past the slides in the carbs and isn't properly compensating. This is where it gets tricky. To test, I use a can of ether. "Start ya bastard", or "engine start" is the action, attach a tube like you get on a can of CRC to the nozzle and spray gently around the carb boots and things. If the revs climb as you squirt in any specific place, you're getting air in there that you shouldn't.

The richening needles that are doing what a conventional 'choke' does, need to seat properly. Like, spot on proper. If they don't, then it can actually cause the same symptoms as an air leak. They can be a bitch to set up, as they are all actuated from a single rod going down all four carbs. So the carbs need to come out, the little lock screws on the rod released so the needles seat, then carefully done back up so they all stay 'synced'.

Time consuming from the beginning, but well worth the fuck around.

The brakes, sounds like they need a service. Pistons taken out, clean behind the seals, and reassembled. This isn't one for someone without experience in my...experience. It's a careful fiddly job, that can go all kinds of wrong with the slightest fuck up. No brakes, is not a situation I would wish apon anyone, after my excursion off the end of the back straight at Pukekoe.

Good luck, post up some results and prgress.