Hey guys, I'm new to the forums just thought I would introduce myself. I am a 20 year old from Sydney who has recently purchased 2 ZXR 250 A models, both in pretty rough shape, one has an engine knock. In 2 months when I have a bit more time I plan to strip both completely down and build one clean example. The ZX with rego and no engine knock has a problem where it refuses to rev past approximately 16K rpm. I have cleaned the carbs and replaced the carb boots and lines which lead off the carb boots but still have the same issue. After cleaning the carbs it would rev to 16K as opposed to the previous 14K hesitation. Strangely if i slowly ease on the throttle gradually the bike will pass 16K however if I wide open throttle it it will pop and stay at 16K. Additionally the bike feels down on power and is very hard to start (full choke and a fraction of an inch of throttle). I have checked the main jet sizes and they are (left to right) 122, 125, 125, 122. My bike is an A model and should have sizes 125, 128, 128, 125 from what I have read on previous posts. If I purchased the correct sizes do you think this would free up the hesitation or it's another issue? Additionally how would I identify if my engine is from an A or C model bike as I know it may have previously been swapped out? Cheers
first step is to check your engine number if it says zx250a.... then its an A model engine, if it says zx250c... then you have the wrong engine for your bike. Lets start there before moving onto jetting
kiffsta may be right the a model and c model have different cdi's which will cause the hesitation up top.
Engine number starts with ZX250AE so its an A model engine. CDI has a B on it model 21119-1263, 131800-5250
Hi there look megazip hit English Lang choose bike and it has right number that go with each model and all parts in each section and tv here number for ordering Sent from my iPhone using Tapatal
You have the right engine and cdi, so i would wager its those mainjets, put the correct 125,128,128,125 in and you might be sweeeet Save buying them and check the other bikes carbs. Probably are the correct ones
Update: The parts bike also has an A model engine and had the correct carb jets. Swapped them around and the bike picks up much better now however still a slight hesitation.
the hesitation could be a number of things, but I would hazard a guess that there could be an air leak, either in the carbs themselves (search litetek kit here on the forums) , the carb boots or the vacuum lines from the carb boots
Thanks Kiffsta! I think i've come to the point where it's best to wait until the complete stripdown of both bikes and replace all lines rather than spend time trying to find the problem. Only two more months until my uni break so will strip both carbs down first and build one using the litetek seal kit and see how it runs. I also think there is an air leak somewhere in the system but I have changed the carb boots and vacuum line already so it may be hard to diagnose. Can't wait for the build, will post a thread as soon as I start!
So I noticed that the rattle from my engine was getting worse. As suspected it was the cam chain tensioner. Removing both tensioners, cleaning all parts and building one with the least wear fixed the issue and the rattle has disappeared. Very thankful I did not have to replace the cam chain. Videos below: Before: After: The exhaust is very loud so it is a bit hard to hear
