NSR 125 Derestriction questions

[Jamrock]

I'm going to be taking my A2 test in January and want to stick with the 2001 NSR 125 for a little while yet before I go and splash on something big. Obviously once I have passed the test I can have a bike of up to 33bhp.

I was curious as to the impact of each restriction taken out, for example if I just derestricted the exhaust how much of a power gain would I get? and how badly would the restrictor in the intake bottleneck the performance. And same the other way around, how much performance gain would I get from leaving the exhaust one in but taking the intake restrictor out?

I'm curious as I want to do them gradually and not both at the same time, so knowing which one raises what will help muchos!

Cheers BCF!

[ncrn]

By doing one and not the other you won't notice much of a difference, and to be honest you could cause damage to the engine. They are designed to run either in as a pair or out as a pair.

To be totally honest the power difference will feel massive to you at first, but realistically you will only be gaining around 10-12bhp so the step up isn't gigantic, you'll get used to it quickly.
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Past: 55 Sym Jet, 91 ZZR250, 03 NSR125R. Present: 97 ER-5.
https://www.nsr125.co.uk - NSR Owners forum.

[Stav]

I may be wrong, but I don't think that's quite how it works. I believe that the intake and exhaust restrictions work in tandem.

I derestricted mine the day after I got it and to be honest the power change although noticeable isn't particularly scary and fully derestricted it makes about 28 bhp iirc. If you do it don't forget to up jet the carb and change the plug as in the umpteen threads in the workshop forum.

Worth doing though as it brings the bike to life...
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Present> 03 Tuono RSV1000 - Past > 02 Honda NSR125RR > 02 Triumph TT600
Cage> 03 Audi TT

[Jamrock]

Yes cause I have a UK model I have to upjet to a 138 main and leave the rest alone. When you say change plugs do I just put a new plug of any kind on there? I'm assuming it's to cope with the new jetting and such.

[Stav]

Can't actually remember as i got rid of the NSR a couple of years ago, but if you search the workshop forum you'll come across the recommended plug, I believe that it gives a hotter spark or something..... use the search function.

Also I believe that you need to change all the jets again as recommended and set the needle to the 2nd notch from the top.

Hope that helps....
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Present> 03 Tuono RSV1000 - Past > 02 Honda NSR125RR > 02 Triumph TT600
Cage> 03 Audi TT

[Mr Hammers]

Plug is BR9EIX.

Cheapest i've found is here for £6.47.
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[Jamrock]

Thanks for all the info guys, I'm a bit OCD about getting info way before I do the job so this gives me time to book it in the garage and ask them anymore questions.

I've tried searching for the 138 main jet but can't find any info or items to buy anywhere. Any ideas?

[Mr Hammers]

You can buy them direct from dellorto.
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