ZXR250 - hesitation and stalls when warm

[ducatilover]

Stupidly fast was in comparison to the fzr250

yeah well in my experience their has been two problems with 400 and 250 owners

1 people bolt on parts and dont change the fueling or they come to a forum and get told a whole bunch of rubbish and still dont get the fuelling right. hardly any of them get their bike gas realized on a dyno to get the fuelling right

2 no one deals with the fundamental issue even though they agree there is a limiting factor and that is the HP limit. if you dont remove the HP limit adding bolt on parts wont make that much difference upto. im sure i'll get over 40hp on the dyno because im dealing with it's issues. fuelling and the hp limiter.


The mc22 would probably be a 40hp limited bike, that doesn't mean you can't get more than 40hp out of it though. i might point out that the 400's are also HP limited

Got any links to info on the 45hp laws? I never knew it existed, only the 40hp law.
I'd be very, very surprised if you got 40hp on a Dyno with a ZXR, unless it's correcting it for crank HP by using the drag off the throttle to calculate the percentage of power lost, then you'll get over 40...I will put money on the dyno being set up to correct it and make a predicted crank hp rating. Otherwise you had the most powerful 4 stroke 250 I've ever heard of.
I've only ridden one 40hp MC22, the rest have been earlier with the 19,000rpm redline, restricted ones had the same rev counter as an MC19, 18,000rpm redline. I've never been on a restircted ZXR either, only A and early C models.

How is the HP limited in the 45hp ones?

BTW a 40hp 250 will generally make 32 at the wheel.
My VT250 Spada did 32 standard.

[Ultrasonic2]

Yes it is possible the dyno was calculating fly wheel hp i couldn't tell you for sure.

With out even tying i found 2 you tube videos for over 40hp at the wheels crb250's
http://www.youtube.com/watch?v=xIeIc2m5N00
http://www.youtube.com/watch?v=slNkOdFD22k

You can find over 40hp ZXR's on the net too.

And here we go on the hp restrictions prior to 1993
http://bikerpat.blogspot.com/2007/06...superbike.html

like i said once you understand the bikes were limited removing the hp limiter can obviously release previously un tapped power.
But really i didn't need to post a link to the hp restrictions it just takes common scene. 3 different bikes all making the same HP, thats impossible with out some hp limiting going on. You can also clearly seeing this going on with the 4 hundreds.

peace out my friend

[ducatilover]

Cheers man, great stuff to read and now I'm more educated.
I am impressed (very) with those HP figures from those CBR's!

[Ultrasonic2]

i've been thinking over the past couple of nights and this is where im at

1. Slide Spring
2. Slide Diaphragm
3. Vacuum Slide
4. Vacuum Port
5. Needle Jet
6. Main Air Jet
7. Main Jet
8. Slow Jet
9. Idle Mixture Adjustment Screw
10. Throttle Plate


Right so there are only 2 ways that fuel enters, this is via the Slow jet(8) and Main jet(7)

The idle mixture adjustment screw allows part of the slow jets fuel(8) though at idle and beyond. But the max fuel this can allow though is ultimately limited by the jet it's fed by the slow jet (8)

The slow jet has it's own out let to deliver is maximum fuel that it's restricted

When the engine is at full rpm and at full open throttle the maximum fuel is delivered by this circuit and it is solely based on the slow jet size. whether or not the fuel is coming from the slow jet hole or the idle mixture screw hole at the same time, because all of this fuel has to pass though the slow jet.

SO It is true that adjusting the mixture fuel will affect the air fuel raito's at low vacuum settings but ultimately at full vacuum it will have NO affect at all, as the slow jet is already delivering is max fuel whether or no it is 1 or 3 turns out

It is also true that 9 and 8 can't be stopped once delivering fuel.



Cool im having fun

[ducatilover]

Now get a gas analyser and see how much difference the idle screw makes. It's naff all over 3000rpm


Carbs are fun things though aren't they?

[Ultrasonic2]

Now get a gas analyser and see how much difference the idle screw makes. It's naff all over 3000rpm


Carbs are fun things though aren't they?

well that was a comment on the carbs pictured. i know mine has another potential inlet . though i thought it was blocked off

i wish all carbs were the same though it would make everyone's life easier

[ducatilover]

Yours work the same as all the ones in my garage man

[Ultrasonic2]

on the up side there really shouldn't be any problems with me running more than 3 turns out. i really want to go back to 3-1/4 3.5 out which it idled better at

[ducatilover]

on the up side there really shouldn't be any problems with me running more than 3 turns out. i really want to go back to 3-1/4 3.5 out which it idled better at

You could go up one size on low speed jet? What size are yours? I might have some floating around.

[Ultrasonic2]

#35

and it probably should be bigger. i have looked for a biker one with no luck so far

[ducatilover]

#35

and it probably should be bigger. i have looked for a biker one with no luck so far

Damn, I think the ones in my 400 carbs are 35's too.

[Ultrasonic2]

oh well :-)

i'll put the new CDI in this weekend since i wont beable to take the carbs off

[Ultrasonic2]

i just plugged the CDI in and it doesn't work .FFS

[ducatilover]

Is it new or second hand?

[Ultrasonic2]

it just cuts out at the lights every 10 minutes if i just wait 5 minutes it will work for another 10 minutes

i tried 0.3mm shims under the needles but that was no good. I will try 0.1 and if that doesn't help i dont think there isn't much i can do next. i would love to try a different tapered needle as i think that would be better than lifting it's height.

i really struggle to understand how the issue can happen.
From o - 18krpm Full throttle is fine
low throttle is fine

Cranking the throttle open below 6k is fine.
Cranking the throttle open above 10k is fine
The closer it gets to 9k the worse the problem gets.
Im still confident the bike is to lean