ZXR 250 Restriction

[backfru]

Maybe this has been asked before, but I've just registered and can't find an answer anywhere else.
I own an '89 ZXR 250A and was wondering how I would go about derestricting it. I've read it various places that it may be washers in the carbs, or something in the airbox, even the CDI or something.. and I am sure it's restricted, I can't even get it up to 180.

Any ideas would be great.

[Hitcher]

Welcome to Kiwibiker.

To deal with your technical question, how fast do you think a four-stroke 250 can go? 180kmh seems more than enough to be going on with, for mine.

[backfru]

Well the fact that I can't even get 180 out of it seems.. a little annoying

[Hitcher]

I think you'll find there aren't many 250s around that will top out much over 150kmh. Anyway, riding bikes is about the journey, not about how quickly you arrive...

[John]

If its not hitting 180 then it wont be restricted what is the max its getting to? Maybe get the compression checked, it may be more a mechanical issue than anything else.

I get to 190, and it wont go father even though it has alot more RPM to play with, I will worry about that later, no need for those speeds.

[backfru]

C'mon guys, can you just give me some ideas of where the restrictors MIGHT be so I can check for myself?
It's getting to about 160 at roughly 15-16,000.. and it feels like it's hit a wall or something.

[N4CR]

My 250C keeps going hard all the way to about 175.. I didnt look at the speedo after that 'scary stuff' but I know I accelerated more after that... I would agree with John on this one but I hope it ain't mechanical
Best of luck with the problem!

[Sniper]

Hehehe, Im sure my bike has done over 100kmph, but Im not sure

[John]

C'mon guys, can you just give me some ideas of where the restrictors MIGHT be so I can check for myself?
It's getting to about 160 at roughly 15-16,000.. and it feels like it's hit a wall or something.

Take it and get a service, its an older bike they can loose there kick, so I guess 6th gear in the redline is getting you to 160kmph?

Sounds asthough thats about as fast as it will go.

So many possibilities of restriction its not funny, speedo - ecu - exhaust (go read tristans thread on debaffling wont give you any massive gains).

But its better if you just wait until you can get a new bike when your on your full.

[bungbung]

Maybe this has been asked before, but I've just registered and can't find an answer anywhere else.
I own an '89 ZXR 250A and was wondering how I would go about derestricting it. I've read it various places that it may be washers in the carbs, or something in the airbox, even the CDI or something.. and I am sure it's restricted, I can't even get it up to 180.

Any ideas would be great.

You'll need a really long bit of road to get to 180km/h. The last 20km/h can take a few kilometres, you'll need to tuck in your mirrors, get right down in a crouch etc etc.

[Monsterbishi]

Not to forget that even though your speedo is claiming 190kph, it's probably more like 170... It's a 250 - Physics is well against you...

[John]

Not to forget that even though your speedo is claiming 190kph, it's probably more like 170... It's a 250 - Physics is well against you...

My speedo was tested acurate to 4% dyno'd to 190. When it hit restricter thank you.

[Monsterbishi]

My speedo was tested acurate to 4% dyno'd to 190. When it hit restricter thank you.

That's pretty good for any speedo, at any rate, now add wind resistance and rider ballast and it's gonna be a stretch to get it that high on any track.

[bugjuice]

a restricter kicking in will be like a brick wall against acceleration.
I doubt your bike will be restricted. *Might* have a redline restricter, would you really want to remove that?
It's more than likely that your bike (sorry to say) is running out of puff. The wind resistance for 250s is often enough for the speed to tail off above 150/160. On my lil' CBR250 when it was on Puke, I had to tuk down and throttle it right from Castrol, if I didn't, the speed diff would be up to 10kph at the brakes for the hairpin. It use to race up to 160, then trail to 170, then push really really hard, and sometimes see 185kph. 250s aren't made to be rockets, so most aren't really restricted aside from a redliner.

If you get up to your top whack, then the bike feels like it miss-fires, thats a restricter. If you get up to top whack, and it hovers around that speed, then thats your terminal speed

welcome btw

[John]

That's pretty good for any speedo, at any rate, now add wind resistance and rider ballast and it's gonna be a stretch to get it that high on any track.

Well it manages to get to 190 on the ticker on the road in a relativly short distance, shit if your keen enough you can try it yourself doesnt take much to get it off the clock - there has being some slight engine mods done to the bike which allows it to go so nuts, I will be checking the bore width when I can be screwed to check that, but I know I have modified carbs and different gearing.

Either way, just to reinforce what I said get it checked out, but if its hitting the redline in top gear its not going to get any faster sadly.