Qustion from a newbie----Flat Spot

[2wheels in Red Beach]

Any ideas...... I will be cruising along 100 or so k's start to excelerate then hit a flat spot to the point of decelerating then all of a sudden the power will kick in again. would this be something obvious.

[marty]

could be anything - a flat spot on the tx curve maybe. i trust your not asking your 250/4 to accelerate from 100 in 5th/6th gear?

[2wheels in Red Beach]

It can do it fairly comfortably, but lately seems to stuggle.

[marty]

how bout that 30 knot head wind you've always got up there on the peninsula?

[2wheels in Red Beach]

lol....yup. i do get that as well but that has a different feel to it. the engine all of a sudden picks up quickly from the flat spot.

Any way wot ur saying.....ur saying I got a slow bike or wot.....

[SuperDave]

My 250 accelerates from 100kph in 5th or 6th quite comfortably up until 170kph - but then again, acceleration is all relative, to me my 250 is relative to my old FXR150

I felt a flatspot similar to this once when I was test riding the ZXR, I believe it had to to with trying to fling the throttle open wide very quickly though. Just easing off the throttle and then trying to reopen it seemed to fix the problem fine. Have yet to have it happen to me since.

[2wheels in Red Beach]

I have tried easing off the throttle and then tried to reopen it slowly
I have tried easing off the throttle and then tried to reopen it fast
I have tried easing off the throttle quickly and then tried to reopen it quickly and repeated a few times as if revving.
It just seems to make it's own mind up to put gas on again.

It's not good when I have some idiot in a cage right up my arse

[Gremlin]

What revs are you running when you try to accelerate? My zzr has a big flatspot about 4-5k, and speaking to JSG (who has a zzr) he also has it.

Two solutions I've found:
1. Run a higher gear. Accelerating from 6-10k is no effort besides twisting the wrist
2. Depending on the gear (mine seem to have different ways of behaving) some, if you gently open the throttle and allow it to build, you might be able to minimise the effect.

Riding a 250 (even a quick one like the zxr or cbr) you have to, have to use the gears. Big bikes have power from 2-3k I believe. I have most of my power beyond 9k.

For fast acceleration, drop 2-3 gears, then go

[TwoSeven]

What rpm and gear is it doing it in ?

[2wheels in Red Beach]

It is doing it in 5th gear (top) at around 10 rpm. but not always. (although seems to be getting more frequent) is it ok to drop down to 3rd at 100-110 k's? Sorry for any silly questions.

[SuperDave]

I'm no expert but I believe that dropping down to a too lower gear whilst still going fast then trying to rip the throttle open is gonna cause valve bounce (?) which is bad and can screw up your engine. Someone correct me if I'm wrong.

[thehollowmen]

I'm no expert but I believe that dropping down to a too lower gear whilst still going fast then trying to rip the throttle open is gonna cause valve bounce (?) which is bad and can screw up your engine. Someone correct me if I'm wrong.

Yes I'd say that's about right but you'd have to go over the redline to do that.

[2wheels in Red Beach]

My redline is 18 i am only at 10-11 when in fith. maybe i will only drop down one gear then. to try and get some more power.

[Hitcher]

Most four-cylinder 250s, in my experience, have a flat-spot somewhere in their power range. Some worse than others.

[Gremlin]

My redline is 18 i am only at 10-11 when in fith. maybe i will only drop down one gear then. to try and get some more power.

yep, the cbr and zxr rev very high, your power is high up in the rev band. Before you accelerate, just drop a gear (maybe two, depending on your revs) and then roll it on and grin