Derestricting an NSR

[nsr125YRH]

Hi everyone

I have an Italian import NSR 125 at least that’s what I think it is...

So I had a rough look on here and found most people say the restriction is in the exhaust and inlet to the carb well this is a picture of the exhaust and as u can see there isn’t a restrictor in this

I also looked at the inlet to the carb and found this

After both of these I took it out and still could only do 65mph

I looked at the CDI unit and another item and this is what it looked like

I heard that the Italian import can’t rev above 10.5 revs but I got mine up to 11 thousand revs before I changed gear

I can only do 65mph but it doesn’t seem to matter about wind or uphill it still does 65 and I haven’t been downhill yet as to be honest that would be cheating haha

I bought this bike thinking it would be rapid and fast for a 125 (90mph) but my old 50 used to do 60 so it’s not a great improvement

pictures below are everything i have described in here

Any help would be much appreciated

Thanks in advance
:)
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honda baby

[Willson]

NSR is a two stroke yes?

Not massively clued up on them but I believe there could be something to do with the exhaust.

A nice little animated picture below, but basically the engine will work more efficiently if it's not blowing out fuel/air mixture.

https://www.instructables.com/image/FCPAPL1F8QANFPB/Two-Stroke-Theory.jpg
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Benson: Wouldn't life be easier if we were all turtles?
Me: Pig on bread = The way forward.
Riding: '00 Suzuki SV650S. Previous: '99 Kawasaki ER5 - sold, '02 Suzuki GZ125 Marauder - sold

[Nope.]

If it is a two stroke, the restrictors will be in the exhaust. A small washer in the manifold and there might also be tubes coming off the side of the exhaust that go no where, these need to be cut off and the holes welded up. Another thing some manufacturers do on 125 two strokes is put restrictions in the expansion chamber itself which often requires a new exhaust to be fitted due to the difficult nature of expansion chamber modification so you may wish to look into this.

If it is just a washer or back pressure pipes you'll need to upjet 3%-5% once you've removed them.
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Former: Derbi GP1 50, Sachs XTC 125, Suzuki GSXR 400 GK73A, Kawasaki ZX7R, Suzuki DR250, Yamaha RD350
Current: 2011 Yamaha XT660Z Ténéré, 2003 Yamaha YZR-R1 5PW (In Build), 2009 Kawasaki ZZR1400

[anthony_r6]

Isn't the Italian model restricted in the electronics somewhere?
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Ted : "Maybe he's agoraphobic."
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[Kickstart]

Hi

UK NSR would be restricted in the exhaust and the intake. Older Italian market one would be totally unrestricted as standard. However even restricted it should easily do more than 65mph, with the exception of those for some markets restricted to low speeds (some German market ones for example).

First thing I would suggest is give the bike a good service and check the compression.

All the best

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

[UKRedwing]

[nsr125YRH]

the bike has been serviced and it the w reg foxeye model and as for compression testing how much and where would i be able to get it done

does the amount of compression really slow your bike down that much?
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honda baby

[Kickstart]

Hi

You test the compression using a compression tester (basically a pressure gauge that latches the reading and screws into spark plug hole). Should be 143psi give or take 28psi (from memory).

The NSR doesn't have a specified service interval for the changing of the rings, and compared to the RS125 the rings are pretty long lived. But they will eventually wear out.

And yes low compression can lose you loads of power.

All the best

Keith
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[UKRedwing]

Hmmm according to wikipedia

"Italy

This has the frame number ZDCJC22A or ZDCJC22D (D is a sport styling model.)

This bike has restrictions in the exhaust."

Your bike is deffinetly the italian model looking at the frame number. Not sure how true the italian models being restricted via exhaust is, always thought they were full power from standard. Exhaust looks unrestricted form your picture anyway.

As kickstart said do a compression test and anything below 130 psi is bad,
do you know when it last had a rebuild, needs piston rings every 7.5k miles and a complete top end rebuild every 21k miles

Edit: Btw check the needles in the carb, full power sizes are 138 main 42 idle 65 power

[skatefreak]

I'm a little dubious about the 7.5k/15k rings/piston stuff I keep hearing.
I met a chap opposite my house who just so happened to be on a tidy NSR identical to mine (seen the bike many times) and he's had this bike from new, 22k on the clocks, de-restricted within a week of owning it, all services and work done by a mechanic but not a single thing done on the engine (no rings/pistons etc)!
I've heard him coming a going a couple of times to and he doesnt hang about so I'm beginning to wonder if rings really are needed every 7.5k?

I dont suppose anyone has a genuine service interval sheet for these things?

-Jvr

[UKRedwing]

[Kickstart]

Hi

Honda do not list the rings being changed as a service items at all. Does list exhaust port and cylinder head decarbonisation at 5k.

Think people on here have done 30k on an NSR without changing the rings.

The NSR has an extra bridge piece across the exhaust port which I suspect gives the rings a FAR easier life than those on an RS125 or Mito (probably at the expense of a tiny bit of power).

All the best

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

[lozza]

yup the italian is totally derestricted from stock.

i'd be looking at compression for definite, if thats not at fault have a go at decoking the exhaust - all it'll cost you is the price of some caustic soda and a new exhaust gasket. and as said as well clean the carb out nicely and check the jet sizes.

also if its got a fair amount of miles and your not sure of the service history check the plug condition and replace if necessary i always find that gives my bike a nice boost.

[alains]

as wanted by your PM , download my file https://www.geneva-racing.ch/~alains/NSRtips.doc
your serial number shows that your bike is unresytricted except this :
- underjetting (you require at least 138,42,65)
- bad sparkplug , you need BR9EIX
- bad reeds membranes , buy those (you can trust them) https://cgi.ebay.de/JOllify-Carbon-Membrane-Honda-NSR-125-R-JC22-036-/160568283756?pt=Motorrad_Kraftradteile&hash=item25629d926c
- poor exhaust system as honda's are , you can buy any race pipes the cheapest is tyga-performance for the 150SP
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the worst day fishing is better than the best day working

[nsr125YRH]

ok so lets say i buy just the jets and the sparkplug and fit them. would i be able to buy the rest later on and still get a performance upgrade without these for now.

also once upjetted and new spark plug do i need to do anything or just run it like normal?

And one last question what do the membranes do and where are they located

thanks again
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honda baby

[lozza]

[nsr125YRH]

could be because atm the sparkplugs most probably never been changed before not sure but im gonna put the better one in tomorrow and the jets and then i will see if it makes a difference ill keep everyone updated
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honda baby

[Kickstart]

Hi

The things Alains mentions are going to get the bike running better than standard if it is in good condition. Maybe a couple of mph increase in top speed. Not going to account for the ~30mph you bike is down on top speed.

Spark plug is probably not going to give you much. Long before it would have lost you 30mph the bike would probably be unable to start.

All the best

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

[nsr125YRH]

so what would you suggest would be the loss of power?
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honda baby

[Kickstart]

Hi

First thing to check is the compression.

Could also be worth checking the ignition timing (not meant to be adjustable, but some faults could cause major issues). Also check the power valve operates and is adjusted correctly (although I would expect it to still do more than 65mph if the power valve wasn't working).

All the best

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

[lozza]

^ +1

[nsr125YRH]

ok so how do i check the powervalve setting? pictures would be much appriciated
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honda baby

[Kickstart]

Hi

Best to check the manual for details on that.

First thing is does the power valve operate when you switch on the ignition.

All the best

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

[nsr125YRH]

i have no idea haha
____________________
honda baby

[lozza]

https://www.mediafire.com/?i5724g515r0o1wo

says JC20 but all the important stuff applies to the JC22 as well.

find the powervalve calibration bit.

the valve is controlled by an electric motor. look between the tank and the frame on the right hand side of your bike, just in front/under the air box theres a small plasic block with a metal pulley on the top and two cables around the pulley.

basically start the bike, warm it up first because youll need to rev it up past 7000.

it should stick at one position, then move when you go over 2000 rpm. then start to move back to the original position once you pass 7000rpm. it moves gradually at this point i think to rev it all the way up to about 10 to make sure.