NSR 125 Gears

[Fladdem]

I searched but nothing related came up.

My mate owns a 2000 Honda NSR 125, it has some stuff done to it, pipe, air filter, re-jetted. We believe standard sprockets. The top speed is about 90mph. Which is about right.

My question isn't about the top speed. Sixth gear is practically unusable apparently. He says he has to rev the nuts off it in fifth to get into sixth without the revs dropping off completely. He says top only has a place if he's doing a top speed run.

Can anyone else confirm a similar thing on theirs? Our current and latest theory is that the engine isn't producing enough torque to pull the standard gearing efficiently. E.G. Perhaps gearing more designed for acceleration may also help with top speed, being easier to pull. You know how when cycling sometimes your legs aren't strong enough for a gear and sometimes you have to change down and can get more speed that way?

Another theory is that it is simply an overdrive gear, and no matter what gearing is run the gearbox is just designed to drop the revs at speed.

Any help would be much appreciated.

Thanks.
____________________
Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[SQL]

sounds like its over geared

[bodger]

I am guessing the engine could have had work done on the ports. If so, it will have a narrower power band. If the revs drop out of this band the engine will bog down. It gets tricky keeping it in the power band the higher the gear you go.
It might help as you said lowering the gear slightly.
This is assuming the engine is in good nick of course.

[skatefreak]

Nope,
standard gearing and 6'th should be plenty usable.
Even my de-restricted NSR after 4 years on the same top end and well over 10,000 miles and it was still pulling plenty in 6'th.
I would expect a stock NSR, de-restricted to pull above 90mph and if you have an after market pipe pipe then even more so.
Sounds to me like its not running quiet right.
What pipe is on there and what jets are in the exhaust?
How many teeth on the sprockets and you say some work has been done to the 'air filter'? Could you elaborate on what was done to said air filter?

There is always a chance the dimensions of the exhaust have changed the tune of the engine negatively, if you could throw a stock exhaust on there ad see how it runs that could help.

Sounds like its running okay if you are getting to 90 and its not mis-behaving however your 6'th gear should be usable...

Best regards

-Jvr

[thomp1983]

2 stroke presumably, where do you want to start? Who did the work? What exhaust and air filter have been fitted?

[Fladdem]

It's my mates bike.

I was wrong it just has a gianelli pipe on it, standard air filter and jets.

11,000 miles on original piston and rings, I think that they may need changing soon.

It's the standard gearing, apparently. Although to me it sounds over-geared. I was wondering if the standard gearing is used to maybe restrict it or something.

It's basically standard apart from the pipe, apparently the PO said the exhaust rusted through.
____________________
Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[thomp1983]

If it's an aftermarket pipe designed it'll probably be running a bit lean but not massively so. He hasn't done anything daft like drill loads of holes in the airbox has he?

[Fladdem]

No, nothing like that. I know that because we were cleaning the air filter today. It wasn't that dirty but we thought it might have something to do with it.

How would we check if it was derestricted or not? His licence means he's stuck on a 125 for a bit so he wants to get it spot on until he can get a bigger bike.


here's a pic of it.

[img] https://scontent-a-lhr.xx.fbcdn.net/hphotos-frc1/t1.0-9/1606892_761060653911772_973617562_n.jpg
____________________
Current:1991 Honda MT50 (Soon to be a H100/MTX/MT5 hybrid), 1976 Honda Cub C70, 2005 Honda Varadero 125, 1993 Yamaha TTR250 Open Enduro , 2010 Road Legal Stomp YX140, 1994 Honda CRM 250 MK III, 1999 Cagiva Mito 125, 1992 Honda CB400 Super Four, Stomp T4 230, 1984 Honda H100s, 2009 Sym XS125K
Past:2003 Aprilia RS125, 1982 Kawasaki GPZ550(FREE BIKE!)
I'm having more fun than a well-oiled midget.

[thomp1983]

What colours the plug?