honda ns125rk flat spot @2500-4000rpm help!

[livin_in_sinn]

hello, i am new here and would like some advice,
i just bought a 1989 honda ns125 rk, and it has had the top end rebuilt. i seem to have a flat spot at about 3-4000 revs, any idea if this could be due to it being newly rebuilt? or may it be something else?
i'm gettin a haynes manual soon, but just wondered if anyone had this sort of problem before and what you fif to sort it.
i'd be much grateful if anyone could help.....
please?
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[Flywheel]

hi

ye i get that on my ns125rk nothing to worry about its just the way 2-strokes are.aint nothing you can realy do about it though.

Also just wondered how fast ur bike goes and if it is restricted or not.


Cheers

[baldy]

2 strokes run at high revs and have next to no power at low revs. My nsr has this problem so i just keep it above 4000rpm
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[livin_in_sinn]

thanks for replying, it seems to be like more of a flat spot than i would expect. i mean it begins to rev nice and freely, then sorta dips as it hits those revs.... i've been told not to run it above 6000rpm for at least a few hundred miles as the person who last had it rebuilt the top end. i've been advised by my friend, who has a dt 125 that it shouldnt run like that.
i'll be takin it to a bike repairers soon, and i'm waiting for my haynes manual to come through the post.

and oh yeah, i dunno if it gets done automatically or what, but thanks to whoever moved this post to the right section.

i only rode the bike for the first time on saturday, and its the first time i been on one. i am a speed freak, but only have been going fast in cars. i'll let you guys know what i can do in the bike. but the guy who had it last said he was doing 70mph @6000rpm cruising. and aparantly, thats good for a 125 ns125.
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VTEC

[baldy]

If you're just running it it don't go mad with it just yet. Just ride with the revs under 7k for about 1000 miles and then thrash away
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[Kickstart]

Hi

Restricted it will manage a shade over a true 70mph. Full power it will manage a true 90ish mph.

Normally a 2 stroke with an expansion chamber will have a flat spot at half peak revs, so the flat spot you have sounds at a little too low a revs for that.

How are you opening the throttle? The NSR uses a slide carb so if you just wrench this fully open it will not work properly (there will be virtually no pressure drop through the carb so it will not draw fuel into the air correctly). Open the throttle progressively.

It might be that the jetting is a touch lean at those throttle openings. If so lift the needle up one notch in the carb and see if that improves things.

Twas me who moved the thread by the way.

All the best

Keith
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[ts50x0]

what are you doing at these revs?????? you should be near the redline almost all the time or there is no power. powerband is at 8,000rpm. when your accelerating keep it there!!!!!! youll have lots more fun!

[livin_in_sinn]

my friend who rode it (who has a DT125) said it didnt have enough power at low revs, do trails bikes have a lot more torque at lower revs? from what i know of the use of trails, can i assume that trails bikes are tuned for more torque at lower revs? my ns125rk goes to 11000rpm, and i havent really opened it up higher than 6/7, so i guess it may be just needs runnin in nicely, then i'll let it fly and let you guys know my 0-60 and stuff.
the ns125rk is actualy my girlfriend's, cos she needs somethin cheap to get around and a bike is easier to get than a car, like all you realy need is a cbt and you can start riding. but i got on the machine once and i wouldnt get off. i'm looking to get a bike of my own, but i dunno what to get. I'm thinkin of another ns125. what do you guys think?
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VTEC

[livin_in_sinn]

oh... and many thanks to kickstart for moving the thread to the right place.

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VTEC