ZXR250C or CBE250RR questions

[bawked]

So I've ended up with both a ZXR250C and a MC22 CBR

ZXR:

My zxr started running poorly and not revving past 12k rpm, was sent down to hamilton for work for a couple months so dropped it into cycletreads. A $1000 later, I have a bike that still runs shit.... apparently due to over worn emulsion tubes. I'm dubious as it runs poorly up at the 12k+ rpm range at full throttle, where the main jet should be doing the work. I managed to sort another set of carbs for cheap though, so I'm planning on testing them with the stock jetting to see if the situation is improved.

I have an aftermarket pipe that I imported from overseas, but if i use it I should probably up the mains jets one size. Who is the best person to talk to regarding carbs parts, such as jets and rebuild kits.

Also since it is a 250 i'm sure no one would've checked the valve clearances, who in auckland sells shims?

CBR:

The bike seems to pull smoothly through the rev range, but one thing that I have noticed is a small hesitation below 3k rpm. It's not really a problem, just annoying when taking off from the lights. It bogs, then takes off as soon as the revs have picked up a little. The bike has an aftermarket pipe on it, but I doubt that would affect fueling all the way down there. Sounds like an oversized pilot jet I think?

Also I'll check the valve clearance on this as well.

I relatively new to the whole carb tuning, I've done a efi tuning course and setup a gsxr600 engine with a link g4 storm. But this is a different ball game, so some guidance would be much appreciated.

[nzspokes]

I know a bit about carbs, so ask at the next Sass.

It will be worn needle seats, talk to this guy. Alec. Chances are if he dont have them he can make em. He is in Whitford. I had the same problem on a Kawasaki and was told at a dealership to get new carbs. I got seats from Alec for $10 each I think it was.

[bawked]

I had a chat to Alec, he recommended boring out the emulsion tubes and getting new needles made. I may do that anyway, as we have a mill at work... Getting new needles made will be a different story, might have to get a CNC place to make some on a lathe

[Tazz]

Got a vid of the CBR hesitation? Maybe it's not normal but mine is also like that (not in a way I'd complain about though so yours may be worse, I just thought it made sense considering the rev range. I wouldn't be expecting much power down low considering these rev out to 18k...).
I just ease the throttle on when that low (usually only when I haven't bothered changing down a gear/3) or just keep the revs up when pulling off... You can have them at 8-12k without sounding like you're wanting to race everyone in slow motion.

Sweet spot seems to be from about 10k and mine cruises between 10-12k around 100-120 from memory.

[FJRider]

Got a vid of the CBR hesitation? Maybe it's not normal but mine is also like that (not in a way I'd complain about though so yours may be worse, I just thought it made sense considering the rev range. I wouldn't be expecting much power down low considering these rev out to 18k...).
I just ease the throttle on when that low (usually only when I haven't bothered changing down a gear/3) or just keep the revs up when pulling off... You can have them at 8-12k without sounding like you're wanting to race everyone in slow motion.

Sweet spot seems to be from about 10k and mine cruises between 10-12k around 100-120 from memory.

I agree ...

For a bike that rev's out to 18K .. 3K is not far above stalling ....

[nzspokes]

I would have to guess a blocked idle jet.

[ducatilover]

ZXR:
Runs like shit? Can you elaborate?
You can buy the emulsion tubes from overseas, don't buy second hand carbs
For a basic slip on can, pull the jets out of cyls 2/3 (122 I think, from memory) and chuck them in to numbers 1/4, then buy the size up from Nikau on trademe, for $6 each.

CBR, hesitation under 3k?
This all depends on load and throttle position, so can't really say over teh internets.
But I would look at doing a carb sync, then a set of plugs. Because it's cheap and it's nice to pamper your bitch.
Check the air filter, intake boots etc etc etc
After these you can go set the carbs up.
Or you could just not be used to having a small 4cyl (mind you, my Bandit pulled from any revs with no flatspots and made 45hp too, could load it up in 6th from 2lrpm without flatspots)

Edit, just read you have an aftermarket pipe.
Does it go flat feeling and hollow sounding or "wet" feeling

[ducatilover]

I agree ...

For a bike that rev's out to 18K .. 3K is not far above stalling ....

I've set carbs up on a few and they never have flatspots. You just have to have all your ducks in a row, as with any engine

3k is still 1.5k above stalling and shouldn't be flatspotting

[bawked]

ZXR:
Runs like shit? Can you elaborate?
You can buy the emulsion tubes from overseas, don't buy second hand carbs
For a basic slip on can, pull the jets out of cyls 2/3 (122 I think, from memory) and chuck them in to numbers 1/4, then buy the size up from Nikau on trademe, for $6 each.

CBR, hesitation under 3k?
This all depends on load and throttle position, so can't really say over teh internets.
But I would look at doing a carb sync, then a set of plugs. Because it's cheap and it's nice to pamper your bitch.
Check the air filter, intake boots etc etc etc
After these you can go set the carbs up.
Or you could just not be used to having a small 4cyl (mind you, my Bandit pulled from any revs with no flatspots and made 45hp too, could load it up in 6th from 2lrpm without flatspots)

Edit, just read you have an aftermarket pipe.
Does it go flat feeling and hollow sounding or "wet" feeling

Well the zxr runs nice down low, at 12k and 16k rpm though it has huge dead spots. Between the dead spots it is really nice, and pulls hard. The guy at cycletreads put 2 sizes smaller jets on the inside, and one size smaller on the outside... And he suggested going another size smaller (115) on the insides.

Where can you get replacement emulsion tubes?! That is want I wanted, but everyone says you cant buy them, since they aren't replaceable.

I'll give the CBR a pampering, and see if the issue still remains. My zxr pulls smoothly from 1k rpm all day, so the CBR should as well.

[ducatilover]

Well the zxr runs nice down low, at 12k and 16k rpm though it has huge dead spots. Between the dead spots it is really nice, and pulls hard. The guy at cycletreads put 2 sizes smaller jets on the inside, and one size smaller on the outside... And he suggested going another size smaller (115) on the insides.

Where can you get replacement emulsion tubes?! That is want I wanted, but everyone says you cant buy them, since they aren't replaceable.

I'll give the CBR a pampering, and see if the issue still remains. My zxr pulls smoothly from 1k rpm all day, so the CBR should as well.

Err... smaller jets? Fuck that.
I have a mate that reckons he did his recently, will flick him a message and get back to you

Has anyone actually checked the emulsion tubes are fucked? Or just making assumptions

And has the ZXR got a standard exhaust/filter?

[mossy1200]

I'll give the CBR a pampering, and see if the issue still remains. My zxr pulls smoothly from 1k rpm all day, so the CBR should as well.

Don't think mine would like 1k. That's almost idle.
Wouldn't most 250 fours be 3k to leave from stationary.
My bike seems to launch best at 7k. I can putter off at 2k ok if there is a cage in front of me.

[ducatilover]

The majority of 250/4s will tootle off 2k cleanly if they have all their ducks in a row.

Which is insane when you look at their lobe center and duration numbers, says something about rod-stroke ratio and sexy head flow...
But this is KB, so your bike is normal. Or fucked

[FJRider]

The majority of 250/4s will tootle off 2k cleanly if they have all their ducks in a row.

Which is insane when you look at their lobe center and duration numbers, says something about rod-stroke ratio and sexy head flow...
But this is KB, so your bike is normal. Or fucked

And the majority of those 250/4's owned by site members are NOT new ... and have six figure speedometer readings.

Nothing was mentioned in the first post of this thread ... on the age or distance traveled .. of either bike.

[ducatilover]

And the majority of those 250/4's owned by site members are NOT new ... and have six figure speedometer readings.

Nothing was mentioned in the first post of this thread ... on the age or distance traveled .. of either bike.

Which is why ducks should be in rows as with any machine

[bawked]

Which is why ducks should be in rows as with any machine

This is very true, if every part of the engine is up to spec then there is no reason why it won't run well. Just because an engine has 100,000+ km doesn't mean it's shit.

I bought a second hand set of carbs, to quickly rule out the emulsion tubes. Also if I need to bore them out I'd rather have a spare set, to use as a control/backup. Turns out the set I bought had bigger jets, so don't have to worry about getting them either. And they were cheap as chips.

Took the cbr out for a good ride today and apart from the issue at low rpm, it pulls like a beast. Puts the zxr to shame I think.