ZXR250 hesitation?

[Spoonrider]

Hi guys,

Have something that I noticed with my ZXR250 that people may be able to give me ideas on...

I have been riding the bike quite a bit now the weather has been getting better and have noticed there is a stuttering or hesitation issue between 6 - 8k rpm. It is hard to explain but if you are cruising between that rev range and are applying a little bit of throttle then the issue occurs but if you give it quite a bit more throttle and get over 8000rpm it seems to come right.

Anyone got any ideas what this could be?

Also, these bikes redline at 19,000rpm so what is a good cruising rpm?

[GSF]

I think the term you're looking for is bogging. You hit that spot in the rev range and it feels flat, unresponsive, down on power? Usually a carb issue.

How long has it been sitting around for and how much/what type of riding have you been doing?
Fuel tends to gum up inside the carbs if left for an extended period of time. Carbs could probably do with a clean and balance.

Another thing to keep in mind, try to take the bike for a good run once a week. Like take it on the motorway, at least 30 minutes, let the engine get good and hot.
Burn out all that mucky rich starting mixture, also boil off any moisture that may have gotten into the oil, condensed in the exhaust system, etc.

Good cruising RPM is whatever the bike feels comfortable at. It was built to do 19 grand, so don't be afraid to wring it's neck and make it scream.
I have a Bandit 250 which is also an IL4, redlines at about 17,000RPM - I typically "cruise" on the motorway between 100-120kp/h in third gear, between 12-15 grand. It's making peak power between 14 to 15.

[SMOKEU]

I typically "cruise" on the motorway between 100-120kp/h in third gear, between 12-15 grand. It's making peak power between 14 to 15.

Why?! You should be in 6th gear at that speed if you're just cruising.

[Akzle]

carb issue. needle clips.

you will move the problem. you will never get rid of it entirely.

cruising RPM... dependers. you will feel it. probably just over your phantom 8k RPM.

[haydes55]

Why?! You should be in 6th gear at that speed if you're just cruising.

What I found was on my inline 4 FZR250 is you can't cruise at legal speeds in 6th gear. 100km/h to 110km/h is best in 5th gear, thats when the bike was about 10krpm if I remember right. When I went to 6th it would bog down. After a bit of experimenting 6th gear would cruise well at minimum of an indicated 120 (so probably 110-115km/h).

[SMOKEU]

What I found was on my inline 4 FZR250 is you can't cruise at legal speeds in 6th gear. 100km/h to 110km/h is best in 5th gear, thats when the bike was about 10krpm if I remember right. When I went to 6th it would bog down. After a bit of experimenting 6th gear would cruise well at minimum of an indicated 120 (so probably 110-115km/h).

Something isn't right with the bike then. I had an MC19 CBR250 which was fine cruising at 100kmh in 6th gear at just over 9000RPM, and I would expect any 4 stroke 250cc bike to be fine at 100kmh in top gear as well. The 4 stroke 250cc bikes won't do 200kmh without being extensively modified, so you're still doing over half the redline at 100kmh in top gear with standard gearing. I've never come across a reasonably standard 4 stroke engine that won't easily cruise at half its redline RPM (unless there's something wrong with it).

[haydes55]

Something isn't right with the bike then. I had an MC19 CBR250 which was fine cruising at 100kmh in 6th gear at just over 9000RPM, and I would expect any 4 stroke 250cc bike to be fine at 100kmh in top gear as well. The 4 stroke 250cc bikes won't do 200kmh without being extensively modified, so you're still doing over half the redline at 100kmh in top gear with standard gearing. I've never come across a reasonably standard 4 stroke engine that won't easily cruise at half its redline RPM (unless there's something wrong with it).

It was a shitter on its last legs. Maybe the gearing and power curves were different, maybe my carbs were filled with dirt.

[SMOKEU]

It was a shitter on its last legs. Maybe the gearing and power curves were different, maybe my carbs were filled with dirt.

I think the carby issue sounds about right, my GSXR was like that when it was still going and the fuel tank had a lot of dirt in it. It was also still fine at high revs.

[GSF]

Something isn't right with the bike then. I had an MC19 CBR250 which was fine cruising at 100kmh in 6th gear at just over 9000RPM, and I would expect any 4 stroke 250cc bike to be fine at 100kmh in top gear as well. The 4 stroke 250cc bikes won't do 200kmh without being extensively modified, so you're still doing over half the redline at 100kmh in top gear with standard gearing. I've never come across a reasonably standard 4 stroke engine that won't easily cruise at half its redline RPM (unless there's something wrong with it).

The Bandit can cruise in 6th at 100kph but I don't like it. Too turdy at those revs, plus the Bandit is a bit fatter than the sportier IL4 250s. I'd rather have it geared lower so I can put down some extra acceleration in case of something happening as Auckland motorways are a shitfight. Anyway, IL4 250s aren't much fun to cruise on, I'd rather thrash the shit out of it as it was intended.

[sharp2183]

Cruising in 3rd gear at 120km? Sounds like a great way to shorten the life of the bike. Those inline fours will happily run at 60km in 6th gear, why do twice the speed with half the gears?

[Brett]

Sounds like carbs - as noted before - needles could be worn or such

Cruising - A ZXR250 should cruise very happily at 110kph in 6th gear...all day. I am 100kg and NEVER had problems on my ZXR's even cruising at higher speeds in 6th gear. RPM will be dictated by your sprockets etc...but should be around 10k rpm from memory. Mine used to spend a lot of time up around the red line and never once in 40,000kms gave me an issue. But then my maintenance was top notch.

[GSF]

Cruising in 3rd gear at 120km? Sounds like a great way to shorten the life of the bike. Those inline fours will happily run at 60km in 6th gear, why do twice the speed with half the gears?

In 3rd at 120km/h the bike would be doing around 14,000 and redlines at 17,000. I don't really see a problem with engine wear, oil and filters are changed every 5,000km, valve clearances has been done about six months ago and the cam chain is good, CCT has been replaced so no slop in chain tension. Compression is still fine across all cylinders. I've been riding it like that for the last two and a bit years and the motor is still as strong as the day I bought it, about 20,000km later.

At motorway speeds in 5th gear and above, revs would be starting to get around 10k, which is where the Bandit starts gets sluggish and unresponsive. I've had to take evasive maneouvres on more than one occasion (last time being a Land Rover skidding across the Southern motorway) and the time required to drop a cog in order to get some quick acceleration could've meant the difference between evading and eating shit (in that case, the back end of an SUV)..

My opinion is those small IL4s are meant to be revved hard, it's how they were designed and intended to be ridden. I don't know about ZXRs, CBR250s and the like but the Bandit definitely will not be happy at 60km/h in 6th, it would be chugging badly.
I only get into 5th and 6th if I'm riding it really hard and at speeds which would definitely be exceeding the speed limit (hypothetically, on closed roads, of course )

[ducatilover]

8Krpm is where the needles are lifting under a cruise/roll on.
Being a ZXR it has probably worn the needles or the needle jet is out of round.

Is it running a standard filter/muffler?
They're bloody gutless at 8000rpm anyway and can bog if you give them too much throttle under load below 10krpm, but it shouldn't be too noticeable

[Rhys]

When I had the zxr it was happy around town in 6th and would happily go up hayward or Ngauranga Gorge in 6th

They are a learner bike, so suffer from being thrashed and have minimal maintenance , give it a good tune up .

If you change the oil/filters keep an eye on the can chain they will easily get 100,000 km with out anything major done the motor