Honda NSR125 - Derestricting

[html3333]

Hello BCF, i'm new around here so go easy on me.

The other day i bought an over priced NSR125 (NSR125RV 1997). The engine has recently been rebuilt with a new top end. The guy who sold it told me that the crank and various other bottem end parts were fine.

All is well so far. Touch wood.


Now - I have been reading around the net on de-restricting them, and as i understand it's within the exhuast, reedblock and a servo?

https://www.nsr125.com/derestrict.htm


The other night i took the carb off and the inlet manifold i can safely say that the intake is not restricted, and the thottle is not restricted

Main jet is a 138 and the other jet was a 40 (im assuming it is the idle)

The exahust is standard, and i have not taken it off yet to see if that is restricted.

Top speed of the bike is abour 80mph.


Now two things i wanted to ask were

Would it be worth putting a exhuast system on to the bike?

What is the servo motor? It is located on a little tray and i was wondering what this does? As i read some where that can be a restrictor

I have also been reading that you have to cut two wires? And that there are differernt CDI units.

Thanks.

[dextersaurus]

Welcome to the forum

I've not got any experience with de-restricting bikes, but i can tell you that there are different types of NSR (from different countries) which have been restricted in various ways, depending on where they were made.

USUALLY there is a restriction in the exhaust.

Fitting a new exhaust can help performance, you can get nice arrow performance exhausts, they cost a bomb but bring power up. Would require the jets to be changed to make it work properly though.

A servo motor is basically an exhaust valve for a 2stroke, since they don't have valves... just controls the flow of gasses out the exhaust

Dunc

[N cee thirty]

wait for a guy called alains to come and answer,he will help you
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[Livefast123]

If you put the frame number of the bike up then it's build area can be identified from that. Should be something like ZDCJC22.......... or at least mine is. The letter after the 22 will determine where it is from

A - Italy
C - UK - Exhaust - Inlet and Upjet
B - France - Exhaust - Inlet - Upjet - Powervalve and CDI
E - Switzerland - Very difficult to derestrict, don't even bother!!

Depending on where they are from determines what type of restrictions are in place. The worst are the French and Swiss bikes which have electronic restrictions as well as most of the mechanical stuff.

Main ones to look for are
Intake restriction
Exhaust restriction
Under sized jets - Should have Main 138 Idle 42 and Power 65.

Then you have got the electronic stuff like
RC valve controller - derestricted part number is TV - 78
Restricted CDI - derestricted part number is CI 626

The powervalve will effect the performance of the bike and should be done with the CDI although 80 Mph isn't a bad speed. A fully derestricted bike should do around 105 indicated.

Also every 2 stroke for sale has had a rebuild.......I would get a compression tester and see what it reads. Whilst NSR's are one of the most reliable 2 strokers out there they must be run on top quality synthetic oil to give you maximum performance and engine life.
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Current ride - Yamaha MT-07

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[Livefast123]

If you are in the market for a new exhaust then consider a Tyga. They are well though of in the NSR community and even though it states for a NSR 150 it actually fits the 125. They are much cheaper than the arrow system.

https://tyga-performance.com/site/product_info.php?currency=GBP&cPath=71_815_816&products_id=515

with

https://tyga-performance.com/site/product_info.php?cPath=71_815_816&products_id=524

Or they do a stainless system for £175 plus either £21 for the silencer or £84 for the carbon version
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[html3333]

okay sorry guys for the late reply. And thanks for all the help recived so far.


RC valve controller, which is think is the little box of tricks sitting on the tray under the tank? If so all it has written on the side is " GMN-6MX157F "

Is this restricted? Does it need alter

Where is the CDI located on the NSR?

Yoke number is: ZDCJC22


I started her up a momnt ago and when it hits around 8.5K revs ( i think ) the little motor started turning and adjusting ... I don't how much it is spining as i have no comparison.

[Livefast123]

[Livefast123]

CDI location is under the rear seat lock crossmember (photo 1)

Powervalve controller location (photo 2) If you look through the right side if the frame you can see the part number with a torch (by Alcast sticker)
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[Teflon-Mike]

Sigh.....
Why do you want to de-restrict it?
Why not buy a bigger, faster, more reliable bike to begin with?
Wouldn't be because you are on L-Plates would it?
In which case.... de-restricting it isn't being clever, its costing you money you could use to get your licence and ride anything you like, perfectly legally, to make a tiddler infantesimally faster, inordinately less reliable, and more illegal, than just riding a big-bike 'off-the-books'...... But of course thats scary.... riding a de-restricted tiddler on L's is fun, you think your getting away with something, kidding yourself that you have a 'fast' bike, and getting away with it, because you have an insurance cert to show any-one that asks with the right reg on it.... And you can kid yourself that its worth all the hassle and all the money, and that your a good rider, getting so much out of a little bike, without actually having to prove it to an examiner, or anyone, with teh fail-safe excuse when some-one on an old Honda Super-Dream goes past you, that well, you're only 'allowed' to ride a 125, so it's not your fault....
New here? Being harsh on you?
Maybe.... but, think about it, WHY do you want to de-restrict a 125 to gain, MAYBE an ectre 5-10mph on teh speedo?
If you have a licence to ride a de-restricted bike, flog the thing, get a bigger bike.
If you don't have a licence..... use it to get yourself one, then flog it and get a bigger bike.... meanwhile, save your pennies and pottential hassles, leave it legal, don't fix what ent broke, and put tour energy into doing Theory Mocs and your money into booking the tests!
How to de-restrict an NSR125?
Get a licence Buy a CBR600!
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In responce to Livefast123:

Yoke number is: ZDCJC2280 0D013592

https://i152.photobucket.com/albums/s183/html33/23022011989.jpg

Managed to get the CDI out after pulling bits for ages. Whats the easiest root to get it out? Coulden't come towards the front of the bike as theres plastic all in the way...

Any way here it is. This is the only text on it which is "KBS" and somthing a long the lines of " CI62 " and some other smallprint text. I can barely read it as its almost rubbed away.

https://i152.photobucket.com/albums/s183/html33/23022011993.jpg

https://i152.photobucket.com/albums/s183/html33/23022011986.jpg

https://i152.photobucket.com/albums/s183/html33/23022011985.jpg



Here is the powervalve controller:

https://i152.photobucket.com/albums/s183/html33/23022011988.jpg


In responce to Teflon-Mike. I've always wanted a NSR125 as a project bike to restore. I actually own a CBR600 RR that is restricted down to 33BHP for another 15 months or unless i do part two.

Now i love two strokes, i love the sound and the smell.
So your comments on being illegal are completely irrelevant
Please leave my thread and stop bashing.

[html3333]

So from what it appears - Everything is de-restricted?

Only thing i have not checked is the exhuast.

[slyrob]

If its got the standard exhaust then you should be able to see where its been cut and re welded if the restriction has been taken out. I would definitely recommend the Tyga exhaust, I had it on mine and the difference in weight from the original is phenomenal.
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[Teflon-Mike]

[chris-red]

Mike

The retricted NSR will be about 14 bhp and unrestricted is low 20s bhp.

I would hardly call a third extra power 'infantesimal', I also believe the top speed will go to about 100mph from about 70. Again not a small amount. I also can't see how it will be ' inordinately less reliable', the bike will be standard as Honda intended it, not tuned to within an inch of it's life.
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[Teflon-Mike]

[stevo as b4]

Mike your being rediculous! The guy might have a Hayabusa in the garage too for all i know, but wanting to get the full designed power output out of a small bike that was originally specified before legislation for the uk and other countries stated that you must have 12bhp is not being silly or pointless.

If you had a 12bhp 125 and following the official de restriction process could often double that output, then i think you will find that this will then give the machine in question a totally different character and power delivery, that was always supposed to be there from the factory.

It would be like owning a 33bhp restricted RGV250 which would cough and splutter at over 6000rpm, and then saying oh it's not worth de-restricting to 62bhp as it will either bugger it up or not make it much faster! It would in reality have a massive effect on performance and the bike would be a very different machine to ride and much better for it in terms of clean running, and more responsive.

Your points on L-plate holders riding illeagally de-restricted 125's was fair and correct IMO, but the rest is fairly a load of bollocks pal!

[Livefast123]

Mike has very valid points about ped boi's etc derestricting their bikes. However we are not their mother and if they want to mess with their bike then they should realise that actions have concequences and should be willing to accept them. Their bikes probably won't last long enough to get them into trouble!

Jumping to conclusions is also a dangerous hobby.

I believe the majority of NSR owners these days are mature, licence holding riders like myself and html who maybe want to go back to their youth. The NSR was certainly something I drooled over at school but could never afford.

What could be better than buying your childhood fantasy, restoring it to full power and going for a ride..........or am I getting far too romantic here
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Current ride - Yamaha MT-07

[Livefast123]

Your bike seems to be fully derestricted so should do more than 80 Mph indicated.

I would check that the air filter is clean and give the exhaust a de carb.

Also buy a compression tester and see what compression you are running. Any less than 120 i think and a new set of rings is needed. Don't take somebodies word for it that it has been rebuilt, you need some evidence!
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Current ride - Yamaha MT-07

[lozza]

im wondering if mike has ever ridden a restricted 125 or even a derestricted 125...

the differences between the two are relatively huge (in the NSR's case at least).

as for the point that derestricting the bike will make it less reliable this is completely invalid seeing as the bike was designed to be used at full power and then restricted afterwards so that it was suited for certain markets.

this is shown by the fact that the italian model of the nsr was sold as stock with no restrictions in place. removing the intake and exhaust restrictions from the UK model will make it the same as the italian.

its not tuning - its removing restrictions.

[Livefast123]

Thats what i've done to mine....ahh two stroke heaven....or at least it will be when it's back on the road.

Removing restrictions has no bearing on the reliability of the bike at all, what does have bearing on the reliability of sports two strokes is ped boi stylee maintenance.
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[html3333]

Thanks for the replys guys, both sides of the argument are correct i feel although dont want to get too involved .

LiveFast

[lozza]

check the exhaust as soon as poss - it makes a massive difference.