WARNING: I do not take any responsibility if your blow your engine or cause any damage which has been coursed by from reading this troubleshooter/guide. You have been warned. TINKER AT YOUR OWN RISK!
Right... now the boring bit is over, we can begin.
ok... Because so many people on here are having low rpm problems I’ve decided to make this troubleshooter/guide which should come in handy for people to be referred to. Some of the stuff I'm about to tell you is common sense if you know a fair bit about bikes, if not... not to worry as you will soon quickly pick up on it.
I once was experiencing these problems myself, so a few hours of tinkering in the garage with the carbs and the bike is now running smooth and sweet.
first of all, read through these checks before you start any tinkering.
Things to check...
1. Very Common on ZXR400's Check that all intake rubbers are not torn, ripped, perished or leaking air. (spray the rubbers with karb cleaner where the carbs connect onto and at the cylinder head (while the engine is on of course) if the engine revs high or bogs down, then there's an air leak)
2. Check that the airbox is not blocked with crud, dead flies etc...
3. Check and if you can, clean the air filter.
4. Check around the airbox when it's bolted to the carbs to see any obvious gaps.
5. Check that the carbs are balanced.
6. Check that all the slides in the carb inlets move freely up and down and go fully to the top.
7. Check float heights. How do I do that?
Another good 1 to check is the fuel. Make sure the fuel is free of water or any other liquid that shouldn't be in there. Drain all carbs 1 by 1 onto a unused bit of garage floor, patio or something and see if there is any floating water blobs sitting on top of the fuel you've just drained. If there is, this really wouldn't help at all. It would be advisable to drain the whole tank and refill with fresh fuel.
Ok, if you've done and checked all those things and still having problems, it's most probably a mixture problem. Bogging or flatspots are usally due to an over rich mixture or over lean mixture. Easiest way to check is to take a sneaky peek at the spark plugs and check the condition of them. Here's a guide on spark plug colours.
Tinkering Time... Play at your own risk!
First thing's first, warm the engine up, once fully warm... set idle to ~1350
LEAN
If your blip your throttle from idle and the revs hang at 2000rpm before dropping to 1350rpm that is a sign of the bike running lean. Another sign of the bike running very lean is the bike getting hot very quickly; you'll also find that the fan will kick in at pretty much every junction.
Tinker: Turn the mixture screws out by 1/2 a turn to richen up the idle. Make sure each carb is set to the exact amount of turns.
RICH
If your blip your throttle from idle and the revs drop below set idle I.E. 1350rpm that is a sign of the bike running rich. Another sign of the bike running rich is the bike getting conking out at junctions, lights, stopping etc... you'll also find that the bike will be very hard to start.
Tinker: Turn the mixture screws in by 1/2 a turn to lean up the idle. Make sure each carb is set to the exact amount of turns.
I hope this is of great help to you all.
Any problems, please don't hesitate to ask me.
Regards
Rich
