tuning nsr125f

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

does any 1 no what sort of cheap ish tuning i can do to my nsr125f because i race it in a quater of a mile straight. i have been racing for 3 years now and last year i became brithish champion for my class. I would like to tune it beacuse i am reaching 75 mph in a quater with is good i think for a standing start. I have been geting in the very early 18 seconds! i am 15 and would appreciate any information you could give.

thanks steve
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steve

Trixie · World Chat Champion Joined: 27 Jul 2005 Karma :

Is it already tuned at all or is it currently standard?
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Dead nobodies in company cars...

VFR400UK · Scooby Slapper Joined: 29 Jun 2004 Karma :

The most simple thing you can do is to downgear the bike. you want to be hitting max rev's in top gear as you cross the line. at the moment i suspect you will be flat out in 5th as you cross the line.

As for more power, a full exhaust system would give you a few extra bhp.

You could get things ported, polished and flowed for a tiny bit more power but your ultimatly limited by the design of the engine and your wallet.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

I would suspect that it is still restricted (a stock early Aprilia RS125 will manage a standing 1/4 in about 15.25 seconds with a terminal speed in the high 80s, and the NSR is not much slower). As such the first thing to do is to get the restrictor out of the exhaust.

Unless you are talking about an NS125 (the older steel framed version).

Downgearing would almost certainly help for standing quarters.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

it is currently standard and if i was to gear it down i wouldnt be getting as much speed top end and i no i would be getting quicker of the line but i am doing quite well of the line at the moment.
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steve

G · The Voice of Reason Joined: 02 Feb 2002 Karma :

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

hi keith,

it is a honda ns 125 f, sorry i do not have any pictures of the bike.

i have only owned it for about 5 mounts and only raced it at 2 meetings but at those 2 meetings i was thrashing it around! I shouldnt of been going as mental as i was. Smile

but all in all i think i definatley brought a good bike since i only paid £400!
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steve

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

What changes can be done to the bike in the class you are racing in?

Micron used to do an exhaust for the NS that worked OK. The standard exhaust works well when derestricted and fitted with a DEP silencer, but that is not easy to do (from memory the restrictors are in the middle of the expansion chamber). The airbox was always reckoned to be quite restrictive. Cheap solution was to drill a load of holes in the lid, but I think they did benefit from an S&B or K&N filter.

Doing any of this will require playing with the jetting. Probably best to do this before trying any drag racing!

There was also a big bore kit available for the NS. Think (from memory of a PB test from about 15 years ago) this got them to about 30hp at the back wheel.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

cheers for that keith,

i can do anything i want in my class to my bike at the moment i am winning but the other lads are close! my mate went out and brought a brand new honda nsr 125 spent about £1, 800 on it and then go to race it and i beat him! Smile

jst shows how good this bike really is.
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steve

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Being honest he should have thrashed you, if the NSR is derestricted.

You will loose a load of low down power when you derestict the exhaust, and that might well mean lowering the gearing to make it easier to move off the line again.

Where are you racing? Could be interesting if a load of 125s are racing.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

i race in a club called the nsa ( national sprinting association)

I also race a little honda cr 80 which is a fully tuned engine in a differnt light weight frame and that flys like a rocket goes about 80 mph! ( you may be saying is that it but im only 15 and you have to start somewhere!)
Trying to keep the front end of that on the floor is a mission it is so fast of the line and the noise it defens you!

I have a lot of fun trying to turn around up the other end tho simply because it has no steering! Smile

But i have a lot of fun on this 1 especially when i run it on racing fuel (klotz)
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steve

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Mmm, plenty of meets. Which ones do you go in for?

Going to Woodbridge on Sunday.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

no im not going their sunday i only race about 10 meetings a season. 4 in somerset ,2 in devon ,1 at santa pod, 2 at tempsford and 1 more some where but i cant remember . Smile

some of them are quite big but you get some that are not as busy!

where abouts do you live ?

steve.
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steve

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

I live just outside Stafford (30 miles NW of Birmingham), which is not really convenient for any drag strips. Santa Pod is probably the closest.

Sunday is organised by the 200mph lot, so will include mainly top speed runs. Suspect my Bandit will be one of the slowest bikes there.

Really should stick a new piston in my RS125 and take that out.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

i live iin wickford in essex which is about 45 mins away from london.

santa pod is the closest for me aswell.

so u have a bandit. whats that like? any tuning?

steve.
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steve

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

1200 Bandit. Had it from new, but fancied a bit of a change so it has now been played with a bit. ~150hp. Skimmed and ported head, reprofiled cams and bored to 1216cc.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

thanks for that keith!

I like the sound of your bandit, my mate who i go racing with is 45 and owns about 12 motorbikes. he has a R1 that he raced in bonneville last summer. he is going to attempt to break the land spead record in a streamliner.
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steve

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

do you no how much bhp a honda rs 125 f has ??
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steve

simon1221 · World Chat Champion Joined: 28 Jul 2004 Karma :

Too much

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DNA50 (sorry) ->> TZR125l >> GPZ500S

racer · Two Stroke Sniffer Joined: 29 Jul 2005 Karma :

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steve

priller · Brolly Dolly Joined: 26 Jan 2004 Karma :

You'll see me probably doing some nsa rounds next year, hopefully doing 15s on a tunned rs125.