ZXR 250 A not revving out ?

Unless you know it is knacked or you have moon and back mileage I'd get some advice on how to set the manual tensioner before you look at changing the chain. Else a new auto tensioner. May save you a lot of agro if this sorts it.
Excuse the "get some advice" if you're an ex-honda motogp mechanic! Only listen to the mechanic at your local bike shop if he's actually done it before. A lot nowadays are only really competant at servicing, fitters rather than engine builders, and these 250's are unusual in the UK of course.
Someone on here must have done it.

 

mate i would stick with an auto tensioner, the ones from a gpx fit ( either that or zzr can never remember which one), just grease it alittle and replace it every 10k or so. i would be too scared i would over tension it.

might have a chat with my mechanic who has done plenty of cam chains on zx2's (always has atleast one at his shop whenever i go, most i saw was 4 of them), but you would certainly want an endless chain at 19k rpm.

mine has some scratching on the rocker cover aswell from the previous owner.

 

he didnt have many kind words, he used the c bomb afew times.

easiest to remove engine for the best access (not necessary though), remove cams (also cct) and rhs engine cover and remove a timing gear ( guessing the gear off the crank), feed chain down make sure nothing has moved and reassemble from there.

i think once you open it all up and have a look at whats going on it should make more sense as to what you have to do, but it is a big job and important its all at tdc and stays that way. He also said he has seen the breakable chains used in other bikes but 20k rpm is another story and to just use an endless chain.

just check timing and take some pictures or mark the cams with a permanent marker in 100 spots and make sure its all good and not too much can go wrong.

 

From memory the ZXr250 cannot have a non breakable cam chain fitted without splitting the cases, one member said his mechanic did some minor adjustments to his crank cases to have off some excess cast steel ground away to make allowances for a fixed cam chain to be fitted in the future. I have used breakable chians in the past, the key is to ensure you knock over the ends of the pin so it cant come out. As for tips, please be aware the inlet and exhaust cams are different, if you donwload the manual, step are listed in there.

As stated by AJverma, the Cam Chain tensioner on the ZR250 is a match, considor checking the spring and tensioner while the cam chain is being done. If you are doing the breakable chain with a pin, you wont have to pull the engine out, it can easily be done with the engine in the frame.

Chris

 

My old boy got a street triple he selling

 

If you have the jets then go ahead - no one ever blew an engine up by it being too rich. The worst you'll do is make it fluffy and slow.
You should be more worried about it running lean. I say this a a man who's FZR 250 air box houses a nissan micra air filter and after the EXUP there's some random Japan race exhaust.
Oh, and because I was scared to take the carbs apart it's running standard jetting. Having said that it does run a bit hot sometimes! Eek, what am I doing?

 

The only time to muck around with jetting & needles is when its chained to a Dyno.
You'll most likely decrease the power & performance doing it by ear at home.
There are shops that will do it for less than you might think.

 

definetly don't want anything to move once it is at tdc, maybe check out some youtube video's so you have an idea of what to do.

 

I am averaging 18.1km per litre

 

nice balius manifold you got there i scored one of those myself last year - i found it was a little more restrictive over the stock zxr250 manifold but yielded a really crisp exhaust note!

 

ok, 14L/km is DOUBLE of what a healthy zxr250 chews. mine now runs slightly rich on standard jets at roughly 7.0L/100km. advice is to sandblast the stock exhaust manifold, give it some love with ceramic paint, then use a stock pipe as its loud enough. Our "A" models were built before emission standards after all and are not so restricted when airflow is considered..... the stroke is a mere 39 odd mills and the piston diameter is the size of a babies fist. i highly recommend that you

A: take the carbs out, take the bowls out, slam some pressurized air through the main jests (while they are out of the carbs), check the fuel tank for internal rust.

B: BALANCE the floats.... we have the resources here to show you. make sure the diaphragms have no holes and the needle is in one piece while you are at it, CV carbs are nice and simple.

C: do you have all the seals? I.e; carb to engine (are they hard and cracked?) carby to airbox, (are they all there?) vacuum hoses? (check that the two center cylinders share one hose and the two out cylinders share separate hoses that join. - "A" model only

D: check the Spark plugs too... along with the caps. individually check the plugs against the engine block... RED spark = bad... BLUE = a nice healthy spark.

E: now that you have the bike clean and the above is complete, lets TUNE the carbies...
it may be more cost effective to use a local mechanic.... some can do this job very, very well.
IF you are willing to wait, you can order a $20 pilot screw adjusting tool, and TWO vacuum gauges from trade tools under $100. this way you can not only make the bike start easier, but also make it idle more stably/ consistently/ decline from revvs smoothly and give you a far better riding experience.

PS: please note that you only need the two vac gauges as the bike ZxR250 has a two piston up, two piston down config.


Chris, please correct me on any misleading info.